Document

POS AM 1 esstech-posamsx3.htm POS AM Document

As filed with the Securities and Exchange Commission on November 3, 2022

Registration No. 333-263316

Registration No. 333-260693

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 2 TO

FORM S-1 ON FORM S-3

REGISTRATION STATEMENT NO. 333-263316

POST-EFFECTIVE AMENDMENT NO. 3 TO

FORM S-1 ON FORM S-3

REGISTRATION STATEMENT NO. 333-260693

UNDER

THE SECURITIES ACT OF 1933

ESS TECH, INC.

(Exact name of registrant as specified in its charter)


Delaware (State or other jurisdiction of incorporation or organization)						98-1550150 (I.R.S. Employer Identification Number)
26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (855) 423-9920 (Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Eric Dresselhuys

Chief Executive Officer

ESS Tech, Inc.

26440 SW Parkway Ave., Bldg. 83

Wilsonville, Oregon 97070

(855) 423-9920

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:


Mark B. Baudler Christoph Luschin Alexandra Perry Wilson Sonsini Goodrich & Rosati, Professional Corporation 650 Page Mill Road Palo Alto, California 94304 (650) 493-9300			Amir Moftakhar Chief Financial Officer ESS Tech, Inc. 26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon 97070 (855) 423-9920

From time to time after the effective date of this registration statement.

(Approximate date of commencement of proposed sale to the public)

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box: ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Securities and Exchange Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer

☐

Accelerated filer

☐

Non-accelerated filer

☒

Smaller reporting company

☒

Emerging growth company

☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of Securities Act. ☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

On November 2, 2021, the registrant filed a registration statement with the Securities and Exchange Commission (the “SEC”) on Form S-1 (File No. 333-260693) (the “Initial Resale Registration Statement”), which was declared effective by the SEC on November 10, 2021. On December 9, 2021, the registrant filed Post-Effective Amendment No. 1 to the Initial Resale Registration Statement with the SEC, which was declared effective by the SEC on December 13, 2021.

On March 4, 2022, the registrant filed a filed a registration statement with the SEC on Form S-1 (File No. 333-263316) (the “Additional Resale Registration Statement” and together with the Initial Resale Registration Statement, the “Prior Registration Statements”), which was declared effective by the SEC on March 16, 2022. Pursuant to Rule 429 under the Securities Act of 1933, as amended (the “Securities Act”), the Additional Resale Registration Statement constituted Post-Effective Amendment No. 2 to the Initial Resale Registration Statement with respect to the offering of any unsold shares thereunder.

Pursuant to Rule 429 under the Securities Act, this Post-Effective Amendment No. 2 to Form S-1 on Form S-3 Registration Statement (File No. 333-263316) and Post-Effective Amendment No. 3 to Form S-1 on Form S-3 Registration Statement (File No. 333-260693) (the “Post-Effective Amendment”) is being filed with the SEC (i) to convert the Prior Registration Statements on Form S-1 into a registration statement on Form S-3, and (ii) to update certain other information. No additional securities are being registered under this Post-Effective Amendment. All applicable registration fees were paid at the time of the original filings of the Prior Registration Statements.

The information in this preliminary prospectus is not complete and may be changed. The securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion, dated November 3, 2022

PRELIMINARY PROSPECTUS

130,044,756 Shares of Common Stock

This prospectus relates to the registration of common stock, par value $0.0001 per share (“Common Stock”), of ESS Tech, Inc. as described herein.

This prospectus relates to the resale from time to time by the selling stockholders described in this prospectus or their permitted transferees (the “Selling Stockholders”) of up to 130,044,756 shares of Common Stock beneficially owned by certain former stockholders of Legacy ESS (as defined herein).

The Selling Stockholders may sell any, all or none of the securities and we do not know when or in what amount the Selling Stockholders may sell their securities hereunder following the date of this prospectus. The Selling Stockholders may sell the securities described in this prospectus in a number of different ways and at varying prices. We provide more information about how the Selling Stockholders may sell their securities in the section titled “Plan of Distribution” beginning on page 21 of this prospectus.

We are registering the offer and sale of these securities to satisfy certain registration rights we have granted under certain agreements between us and the Selling Stockholders. We will not receive any of the proceeds from the sale of the securities by the Selling Stockholders. We will pay the expenses associated with registering the sales by the Selling Stockholders other than any underwriting discounts and commissions, as described in more detail in the section titled “Use of Proceeds” appearing on page 6 of this prospectus.

Our Common Stock is listed on The New York Stock Exchange (“NYSE”) under the symbol “GWH”. On November 2, 2022, the last quoted sale price for our Common Stock as reported on NYSE was $3.89 per share.

We are an “emerging growth company,” as defined under the federal securities laws, and, as such, may elect to comply with certain reduced public company reporting requirements for this prospectus and for future filings.

INVESTING IN OUR SECURITIES INVOLVES A HIGH DEGREE OF RISK. PLEASE CAREFULLY READ THE INFORMATION UNDER THE HEADINGS “RISK FACTORS” BEGINNING ON PAGE 4 OF THIS PROSPECTUS AND “ITEM 1A – RISK FACTORS” OF OUR MOST RECENT REPORT ON FORM 10-K OR 10-Q THAT IS INCORPORATED BY REFERENCE IN THIS PROSPECTUS BEFORE YOU INVEST IN OUR SECURITIES.

You should rely only on the information contained in this prospectus or any prospectus supplement or amendment hereto. We have not authorized anyone to provide you with different information.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is , 2022.

TABLE OF CONTENTS


			Page
About this Prospectus			ii
Prospectus Summary			1
The Offering			3
Risk Factors			4
Cautionary Note Regarding Forward-Looking Statements			5
Use of Proceeds			6
Selling Stockholders			7
Description of Securities			10
Plan of Distribution			21
Legal Matters			24
Experts			24
Where You Can Find More Information			24
Incorporation by Reference			25

ABOUT THIS PROSPECTUS

Pursuant to Rule 429 under the Securities Act of 1933, as amended (the “Securities Act”), this prospectus is a combined prospectus relating to (i) up to 125,952,180 shares of our Common Stock previously registered for resale pursuant to the registration statement on Form S-1 initially filed with the Securities and Exchange Commission (the “SEC”) on November 3, 2021 (File No. 333-260693) and (ii) up to 4,092,576 shares of our Common Stock previously registered for resale pursuant to the registration statement on Form S-1 initially filed with the SEC on March 4, 2022 (File No. 333-263316).

You should rely only on the information contained in this prospectus or in any applicable prospectus supplement prepared by us or on our behalf. Neither we nor the Selling Stockholders have authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. Neither we nor the Selling Stockholders are making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus is accurate only as of the date on the front cover of this prospectus. Our business, financial condition, results of operations and prospects may have changed since that date.

This prospectus is part of a registration statement on Form S-3 that we filed with the SEC using the “shelf” registration process. Under this shelf registration process, the Selling Stockholders hereunder may, from time to time, sell the securities offered by them described in this prospectus. Additionally, under the shelf process, in certain circumstances, we may provide a prospectus supplement that will contain certain specific information about the terms of a particular offering by one or more of the Selling Stockholders. We will not receive any proceeds from the sale by such Selling Stockholders of the securities offered by them described in this prospectus.

We may also provide a prospectus supplement or post-effective amendment to the registration statement to add information to, or update or change information contained in, this prospectus. You should read both this prospectus and any applicable prospectus supplement or post-effective amendment to the registration statement together with the additional information to which we refer you in the section of this prospectus titled “Where You Can Find More Information.”

On October 8, 2021 (the “Closing Date”), ESS Tech, Inc., a Delaware corporation (f/k/a ACON S2 Acquisition Corp., a Cayman Islands exempted company (“STWO”)), consummated a business combination (the “Business Combination”) pursuant to that certain Agreement and Plan of Merger, dated May 6, 2021 (the “Merger Agreement”), by and among STWO, SCharge Merger Sub, Inc., a Delaware corporation and wholly owned direct subsidiary of STWO (“Merger Sub”), and ESS Subsidiary Tech, Inc., a Delaware corporation (f/k/a ESS Tech, Inc.) (“Legacy ESS”), following the approval at a special meeting of the stockholders of STWO held on October 5, 2021.

Pursuant to the terms of the Merger Agreement, STWO deregistered by way of continuation under the Cayman Islands Companies Act (2021 Revision) and registered as a corporation in the State of Delaware under Part XII of the Delaware General Corporation Law, and a business combination between STWO and Legacy ESS was effected through the merger of Merger Sub with and into Legacy ESS, with Legacy ESS surviving as a wholly owned subsidiary of STWO (together with the other transactions described in the Merger Agreement, the “Merger”). On the Closing Date, the registrant changed its name from “ACON S2 Acquisition Corp.” to “ESS Tech, Inc.”

Unless the context indicates otherwise, references to “ESS,” the “Company,” “we”, “us” and “our” refer to ESS Tech, Inc., a Delaware corporation, and its consolidated subsidiaries following the Business Combination.

The ESS design logo and the ESS mark appearing in this prospectus are the property of ESS Tech, Inc. Trade names, trademarks and service marks of other companies appearing in this prospectus are the property of their respective holders. We have omitted the ® and TM designations, as applicable, for the trademarks used in this prospectus.

PROSPECTUS SUMMARY

This summary highlights selected information that is presented in greater detail elsewhere, or incorporated by reference, in this prospectus. It does not contain all of the information that may be important to you and your investment decision. Before investing in our securities, you should carefully read this entire prospectus, including the matters set forth under the section of this prospectus captioned “Risk Factors” and the financial statements and related notes and other information that we incorporate by reference herein, including our Annual Report on Form 10-K and our Quarterly Reports on Form 10-Q.

Company Overview

ESS is a long-duration energy storage company specializing in iron flow battery technology. We design and produce long-duration batteries predominantly using earth-abundant materials that we expect can be cycled over 20,000 times without capacity fade. Because we designed our batteries to operate using an electrolyte of primarily salt, iron and water, they are non-toxic and substantially recyclable.

Our long-duration iron flow batteries are the product of nearly 50 years of scientific advancement. Our founders, Craig Evans and Dr. Julia Song, began advancing this technology in 2011 and formed ESS. Our team has significantly enhanced the technology, improved the round-trip efficiency and developed an innovative and patented solution to the hydroxide build-up problem that plagued previous researchers developing iron flow batteries. Our proprietary solution to eliminate the hydroxide formation is known as the Proton Pump, and it works by utilizing hydrogen generated by side reactions on the negative electrode. The Proton Pump converts the hydrogen back into protons in the positive electrolyte. This process eliminates the hydroxide and stabilizes the electrolytes’ pH levels. The Proton Pump is designed to allow the electrolyte to be used for over 20,000 cycles without any capacity fade.

Our batteries provide flexibility to grid operators and energy assurance for commercial and industrial customers. Our technology addresses energy delivery, duration and cycle-life in a single battery platform that compares favorably to lithium-ion batteries, the most widely deployed alternative technology. Using our iron flow battery technology, we are developing two products, each of which is able to provide reliable, safe, long-duration energy storage. Our first energy storage product, the Energy Warehouse, is our “behind-the-meter” solution (referring to solutions that are located on the customer’s premises, behind the service demarcation with the utility) that offers energy storage ranging from four to 12-hour duration. Our second, larger scale energy storage product, the Energy Center, is designed for “front-of-the-meter” (referring to solutions that are located outside the customer’s premises, typically operated by the utility or by third-party providers who sell energy into the grid, often known as independent power producers) deployments specifically for utility and large commercial and industrial consumers.

We began shipping our second-generation Energy Warehouses in the third quarter of 2021 and, during the second quarter of 2022, we received final customer acceptance for the first units shipped. With each battery deployed, we will further our mission to accelerate the transition to a zero-carbon energy future with increased grid reliability.

Corporate Information

On October 8, 2021 (the “Closing Date”), ESS, f/k/a ACON S2 Acquisition Corp., a Cayman Islands exempted company (“STWO”), consummated a merger pursuant to that certain Agreement and Plan of Merger, dated May 6, 2021 (the “Merger Agreement”), by and among STWO, SCharge Merger Sub, Inc., a Delaware corporation and wholly owned direct subsidiary of STWO (“Merger Sub”), and ESS Tech Subsidiary, Inc., a Delaware corporation, f/k/a ESS Tech, Inc. (“Legacy ESS”), following the approval at a special meeting of the stockholders of STWO held on October 5, 2021.

Pursuant to the terms of the Merger Agreement, STWO deregistered by way of continuation under the Cayman Islands Companies Act (2021 Revision) and registered as a corporation in the State of Delaware under Part XII of the Delaware General Corporation Law, and a business combination between STWO and ESS was effected through the merger of Merger Sub with and into Legacy ESS, with Legacy ESS surviving as a wholly owned subsidiary of STWO (together with the other transactions described in the Merger Agreement, the “Merger”). On the Closing Date, the registrant changed its name from “ACON S2 Acquisition Corp” to “ESS Tech, Inc.”

On October 11, 2021, our Common Stock and public warrants to purchase shares of Common Stock, exercisable for one share of Common Stock at a price of $11.50 per share, subject to adjustments, formerly those of STWO, began trading on the New York Stock Exchange under the ticker symbols “GWH” and “GWH.W,” respectively.

Our principal executive offices are located at 26440 SW Parkway Ave., Bldg. 83, Wilsonville, Oregon 97070, and our telephone number is (855) 423-9920.

Our website address is https://essinc.com. The information on, or that can be accessed through, our website is not part of this prospectus and should not be considered to be part of this prospectus unless expressly noted.

THE OFFERING


Shares of Common Stock offered by the Selling Stockholders hereunder			130,044,756 shares.

Use of proceeds			We will not receive any proceeds from the sale of our Common Stock offered by the Selling Stockholders. See the section titled “Use of Proceeds” appearing on page 6 of this prospectus for more information.

Risk factors			See the section titled “Risk Factors” beginning on page 4 of this prospectus and other information included in this prospectus for a discussion of factors that you should consider carefully before deciding to invest in our Common Stock.

NYSE symbol			“GWH” for our Common Stock.

RISK FACTORS

An investment in our securities involves a high degree of risk. Prior to making a decision about investing in our securities, you should carefully consider the risks, uncertainties and assumptions discussed under “Part I—Item 1A—Risk Factors” of our most recent Annual Report on Form 10-K and in “Part II—Item 1A—Risk Factors” in our most recent Quarterly Report on Form 10-Q filed subsequent to such Form 10-K that are incorporated herein by reference, as may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and any prospectus supplement and the information incorporated by reference in this prospectus and any prospectus supplement contain certain statements that constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The words “believe,” “may,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “expect,” “could,” “would,” “project,” “plan,” “potentially,” “likely,” and similar expressions and variations thereof are intended to identify forward-looking statements, but are not the exclusive means of identifying such statements. Those statements appear in this prospectus, any accompanying prospectus supplement and the documents incorporated herein and therein by reference, particularly in the sections captioned “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and include statements regarding the intent, belief or current expectations of our management that are subject to known and unknown risks, uncertainties and assumptions. You are cautioned that any such forward-looking statements are not guarantees of future performance and involve risks and uncertainties, and that actual results may differ materially from those projected in the forward-looking statements as a result of various factors.

Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified, you should not rely upon forward-looking statements as predictions of future events. The events and circumstances reflected in the forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Except as required by applicable law, including the securities laws of the United States and the rules and regulations of the SEC, we do not plan to publicly update or revise any forward-looking statements contained herein after we distribute this prospectus, whether as a result of any new information, future events or otherwise.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus, and although we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted a thorough inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

This prospectus, any prospectus supplement and the documents incorporated by reference in this prospectus may contain market data that we obtain from industry sources. These sources do not guarantee the accuracy or completeness of the information. Although we believe that our industry sources are reliable, we do not independently verify the information. The market data may include projections that are based on a number of other projections. While we believe these assumptions to be reasonable and sound as of the date of this prospectus, actual results may differ from the projections.

USE OF PROCEEDS

All of the shares of Common Stock offered by the Selling Stockholders pursuant to this prospectus will be sold by the Selling Stockholders for their respective accounts. We will not receive any of the proceeds from the sale of the shares of Common Stock hereunder. With respect to the registration of all shares of Common Stock offered by the Selling Stockholders pursuant to this prospectus, the Selling Stockholders will pay any underwriting discounts and commissions and expenses incurred by them for brokerage, accounting, tax or legal services or any other expenses incurred by them in disposing of the securities. We will bear the costs, fees and expenses incurred in effecting the registration of the shares of Common Stock covered by this prospectus, including all registration and filing fees and fees and expenses of our counsel and our independent registered public accounting firm.

SELLING STOCKHOLDERS

This prospectus relates to the resale by the Selling Stockholders from time to time of up to 130,044,756 shares of Common Stock. The Selling Stockholders may from time to time offer and sell any or all of the Common Stock set forth below pursuant to this prospectus and any accompanying prospectus supplement.

When we refer to the “Selling Stockholders” in this prospectus, we mean the persons listed in the table below, and their permitted transferees, lenders and others who later come to hold any of the Selling Stockholders’ interest in the Common Stock in accordance with the terms of the agreement(s) governing the registration rights applicable to such Selling Stockholder’s shares of Common Stock.

The following table sets forth the names of the Selling Stockholders, the aggregate number of shares of Common Stock beneficially owned prior to the offering, the aggregate number of shares of Common Stock that the Selling Stockholders may offer pursuant to this prospectus, and the number of shares of Common Stock beneficially owned by, and percentage ownership of, the Selling Stockholders after the sale of the shares of Common Stock offered hereby. We have determined beneficial ownership in accordance with the rules of the SEC, and thus it represents sole or shared voting or investment power with respect to our securities. Unless otherwise indicated below, to our knowledge, the persons and entities named in the table have sole voting and sole investment power with respect to all shares that they beneficially owned, subject to community property laws where applicable. The information does not necessarily indicate beneficial ownership for any other purpose, including for purposes of Sections 13(d) and 13(g) of the Securities Act.

We have based our calculation of the percentage of beneficial ownership prior to this offering on 152,919,714 shares outstanding as of September 30, 2022. We have based on our calculation on the percentage of beneficial ownership after this offering on the resale of 130,044,756 shares originally offered by the Selling Stockholders.

The information set forth below is based on information provided by or on behalf of the Selling Stockholders prior to the date hereof. Information concerning the Selling Stockholders may change from time to time. We cannot advise you as to whether the Selling Stockholders will in fact sell any or all of the Common Stock being offered hereunder. In addition, the Selling Stockholders may sell, transfer or otherwise dispose of, at any time and from time to time, the Common Stock in transactions exempt from the registration requirements of the Securities Act after the date of this prospectus. In addition, since the date on which the Selling Stockholders provided this information to us, such Selling Stockholders may have sold, transferred or otherwise disposed of all or a portion of the offered shares. For purposes of this table, we have assumed that the Selling Stockholders will sell all of the shares of Common Stock covered by this prospectus upon the completion of the offering.

In computing the number of shares beneficially owned by a person and the percentage ownership of that person, we deemed outstanding Common Stock subject to options held by that person that are currently exercisable or exercisable within 60 days of September 30, 2022. We did not deem these shares outstanding, however, for the purpose of computing the percentage ownership of any other person.

Unless otherwise indicated, the address of each beneficial owner listed in the table below is c/o ESS Tech, Inc., 26440 SW Parkway Ave., Bldg. 83, Wilsonville, Oregon 97070.


	Shares Beneficially Owned Prior to the Offering			Shares Being Offered	Shares Beneficially Owned After the Offering
Name of Beneficial Owner	Shares	%			Shares	%
Executive Officers and Directors:
Craig Evans (1)	5,547,476	3.6	%	5,391,860	155,616	*
Julia Song (2)	2,479,152	1.6	%	2,278,104	201,408	*
5% or Greater Stockholders:
BASF Venture Capital GmbH (3)	9,214,562	6.0	%	9,214,862	—	—
Breakthrough Energy Ventures, LLC (4)	18,559,329	12.1	%	18,559,329	—	—
Cycle Capital Fund III, L.P. (5)	11,292,025	7.4	%	11,292,025	—	—
Entities affiliated with Pangaea Ventures III LLC (6)	13,000,782	8.5	%	13,000,782	—	—
SB Energy Global Holdings One Ltd. (7)	35,954,722	23.5	%	35,954,722	—	—
Entities affiliated with Fidelity (8)	13,200,000	8.6	%	13,200,000	—	—
Selling Stockholders:
Spring Creek Capital LLC (9)	5,000,000	3.3	%	5,000,000	—	—
Entities affiliated with Presidio (10)	5,614,457	3.7	%	5,614,457	—	—
Evergy Ventures, Inc. (11)	3,117,818	2.0	%	3,117,818	—	—
All other Selling Stockholders (12)	8,569,593	5.6	%	7,421,097	1,148,496	*

__________________

*Represents less than one percent.

(1)Consists of (i) 5,332,876 shares, (ii) 112,235 restricted stock units vested or vesting within 60 days of September 30, 2022 and (iii) options to purchase 102,365 shares exercisable within 60 days of September 30, 2022.

(2)Consists of (i) 2,221,478 shares, (ii) 95,507 restricted stock units vested or vesting within 60 days of September 30, 2022 and (iii) options to purchase 162,167 shares exercisable within 60 days of September 30, 2022.

(3)Based on the Schedule 13G/A filed by BASF Ventures Capital GmbH with the SEC on February 11, 2022. The address for BASF Ventures Capital GmbH is BE 01, Benckiserplatz 1, Ludwigshagen/Rhine, Germany 67059.

(4)Breakthrough Energy Ventures, LLC is managed by Breakthrough Energy Investments, LLC, its manager, which may be deemed to have beneficial ownership over the shares and exercises voting and investment control through its investment committee. The address for each of Breakthrough Energy Ventures, LLC and Breakthrough Energy Investments, LLC is 250 Summer Street, 4th Floor, Boston, Massachusetts 02210.

(5)Cycle Capital Management II Inc. is the general manager of Cycle Capital III, L.P., which is the general partner of Cycle Capital Fund III. Andrée-Lise Methot and Claude Vachet, as managing partners of Cycle Capital III, L.P., may be deemed to share beneficial ownership over the shares held by Cycle Capital Fund III. The address for each of the Cycle Capital entities, Andrée-Lise Methot and Claude Vachet is 100 Sherbrooke West, Suite 1610, Montreal, Québec, Canada H3A 3G4.

(6)Based on the Schedule 13G filed by Pangaea Ventures Fund III, LP on January 28, 2022. Consists of (i) 12,546,771 shares held by Pangaea Ventures Fund III, LP, (ii) 166,230 shares held by Pangaea Partners LLC, (iii) 220,892 shares held by Monoc Capital Ltd. (“Monoc”), and (iv) 66,889 shares held by Vicap LLC (“Vicap”). Pangaea Venture Funds III, LP is managed by its general partner, Pangaea Ventures III LLC (“Pangaea GP”). Pangaea GP is managed and controlled by Vicap, PSee Ventures LLC and Monoc, which are owned and controlled by Chris Erickson, Purnesh Seegopaul and Andrew Haughian, respectively. Chris Erickson and Andrew Haughian share voting and dispositive control over the shares held by Pangaea Partners LLC. The address for each of these entities and individuals is c/o Pangaea Ventures III LLC, 5080 North 40th Street, Unit 105, Phoenix, Arizona 85018.

(7)The address for SB Energy Global Holdings One Ltd. is 69 Grosvenor Street, London, W1K 3JP, United Kingdom,. The address of SoftBank Group Corp. is 1-9-1, Higashi-Shimbashi Minato-ku, Tokyo 105-7303 Japan.

(8)Based on the Schedule 13G filed by FMR LLC and Abigail Johnson with the SEC on February 9, 2022. These shares are held by accounts managed by direct or indirect subsidiaries of FMR LLC. Abigail P. Johnson is a Director, the Chairman, the Chief Executive Officer and the President of FMR LLC. Members of the Johnson family, including Abigail P. Johnson, are the predominant owners, directly or through trusts, of Series B voting common shares of FMR LLC, representing 49% of the voting power of FMR LLC. The Johnson family group and all other Series B shareholders have entered into a shareholders’ voting agreement under which all Series B voting common shares will be voted in accordance with the majority vote of Series B voting common shares. Accordingly, through their ownership of voting common shares and the execution of the shareholders’ voting agreement, members of the Johnson family may be deemed, under the Investment Company Act, to form a controlling group with respect to FMR LLC. Neither FMR LLC nor Abigail P. Johnson has the sole power to vote or direct the voting of the shares owned directly by the various investment companies registered under the Investment Company Act (“Fidelity Funds”) advised by Fidelity Management & Research Company (“FMR Co”), a wholly owned subsidiary of FMR LLC, which power resides with the Fidelity Funds’ Boards of Trustees. Fidelity Management & Research Company carries out the voting of the shares

under written guidelines established by the Fidelity Funds’ Boards of Trustees. The address for each of these entities is c/o FMR LLC, 245 Summer Street, Boston, MA 02210.

(9)Consists of shares held directly by Spring Creek Capital LLC. The address for this entity is 4111 E 37th St N, Wichita, Kansas 67220.

(10)Consists of (i) 4,612,031 shares held by Presidio Partners Investment Management LLC, and (ii) 1,002,426 shares held by Presidio-IPM j.s.a. The address for each of these entities is 2181 Greenwich Street, San Francisco, CA 94123.

(11)Consists of shares held directly by Evergy Ventures, Inc. The address for Evergy Ventures, Inc. is 1200 Main St., Suite 2000 Kansas City, MO 64105.

(12)Each of the other Selling Stockholders beneficially owns less than 1.0% of our Common Stock.

DESCRIPTION OF SECURITIES

The following description of our securities and certain provisions of our certificate of incorporation and amended and restated bylaws are summaries and are qualified by reference to the certificate of incorporation and the amended and restated bylaws. Copies of these documents have been filed with the SEC as exhibits to our registration statement, of which this prospectus forms a part.

Our authorized capital stock consists of 2,200,000,000 shares of capital stock, of which:

•2,000,000,000 shares are designated as common stock, par value $0.0001 per share; and

•200,000,000 shares are designated as preferred stock, par value $0.0001 per share.

Our board of directors is authorized, without stockholder approval, except as required by the listing standards of the New York Stock Exchange, to issue additional shares of capital stock.

Common Stock

The holders of our Common Stock are entitled to one vote per share on all matters submitted to a vote of the stockholders and do not have cumulative voting rights. Accordingly, subject to the rights of holders of any preferred stock outstanding at the time, where a quorum is present at a meeting of stockholders, directors are elected by plurality vote. Subject to preferences that may be applicable to any preferred stock outstanding at the time, the holders of outstanding shares of our Common Stock are entitled to receive ratably any dividends declared by the board of directors out of assets legally available. Upon the liquidation, dissolution or winding up, holders of our Common Stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preference of any then outstanding shares of preferred stock. Holders of our Common Stock have no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to our Common Stock.

Preferred Stock

Our board of directors is authorized, subject to limitations prescribed by the Delaware General Corporation Law (“DGCL”), to issue preferred stock in one or more series, to establish from time to time the number of shares to be included in each series, and to fix the designation, powers, preferences, and rights of the shares of each series and any of its qualifications, limitations, or restrictions, in each case without further vote or action by the stockholders. The board of directors is empowered to increase, but not above the total number of authorized shares of preferred stock, or decrease the number of shares of any series of preferred stock, but not below the number of shares of that series then outstanding, without any further vote or action by the stockholders. Our board of directors is able to authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of our Common Stock. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring, or preventing a change in control of ESS and might adversely affect the market price of our Common Stock and the voting and other rights of the holders of our Common Stock. There are currently no plans to issue any shares of preferred stock.

Warrants

Public Warrants

Each whole warrant entitles the registered holder to purchase one share of Common Stock at a price of $11.50 per share, subject to adjustment as discussed below. Pursuant to the Warrant Agreement, dated September 16, 2020, as amended by the Assignment, Assumption and Amendment Agreement, dated October 8, 2021 (together, the “Warrant Agreement”), a warrant holder may exercise its warrants only for a whole number of shares of Common Stock. This means only a whole warrant may be exercised at a given time by a warrant holder. No fractional warrants will be issued upon separation of the units and only whole warrants trade. The warrants expire on October 8, 2026, at 5:00 p.m., New York City time, or earlier upon redemption or liquidation.

Redemption of Warrants when the price per share of our Common Stock equals or exceeds $18.00. Once the public warrants become exercisable, we may redeem the outstanding warrants (excluding the private placement warrants):

•in whole and not in part;

•at a price of $0.01 per public warrant;

•upon a minimum of 30 days’ prior written notice of redemption to each warrant holder; and

•if, and only if, the closing price of our Common Stock equals or exceeds $18.00 per share (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a warrant as described under the heading “—Anti-dilution Adjustments”) for any 20 trading days within a 30-trading day period ending three trading days before we send the notice of redemption to the warrant holders.

We will not redeem the warrants as described above unless a registration statement under the Securities Act covering the issuance of our Common Stock issuable upon exercise of the warrants is then effective and a current prospectus relating to those shares of our Common Stock is available throughout the 30-day Redemption Period (as defined below). If and when the warrants become redeemable, we may exercise our redemption right even if we are unable to register or qualify the underlying securities for sale under all applicable state securities laws.

We have established the last of the redemption criteria discussed above to prevent a redemption call unless there is at the time of the call a significant premium to the warrant exercise price. If the foregoing conditions are satisfied and we issue a notice of redemption of the warrants, each warrant holder will be entitled to exercise his, her or its warrant prior to the scheduled redemption date. However, the price of our Common Stock may fall below the $18.00 redemption trigger price (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a warrant as described under the heading “—Anti-dilution Adjustments”) as well as the $11.50 (for whole shares) warrant exercise price after the redemption notice is issued.

Redemption of warrants when the price per share of our Common Stock equals or exceeds $10.00. Once the warrants become exercisable, we may redeem the outstanding warrants:

•in whole and not in part;

•at $0.10 per warrant upon a minimum of 30 days’ prior written notice of redemption provided that holders will be able to exercise their warrants on a cashless basis prior to redemption and receive that number of shares determined by reference to the table below, based on the redemption date and the “fair market value” of our Common Stock (as defined below) except as otherwise described below;

•if, and only if, the closing price of our Common Stock equals or exceeds $10.00 per public share (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a warrant as described under the heading “—Anti-Dilution Adjustments”) for any 20 trading days within the 30-trading day period ending three trading days before we send the notice of redemption to the warrant holders; and

•if the closing price of our Common Stock for any 20 trading days within a 30-trading day period ending on the third trading day prior to the date on which we send the notice of redemption to the warrant holders is less than $18.00 per share (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a warrant as described under the heading “—Anti-dilution Adjustments”), the preferred stock must also be concurrently called for redemption on the same terms as the outstanding public warrants, as described above.

In accordance with the Warrant Agreement, in the event that we elect to redeem the outstanding warrants as set forth under the headings “—Redemption of Warrants when the price per share of our Common Stock equals or exceeds $18.00” and “—Redemption of Warrants when the price per share of our Common Stock equals or exceeds $10.00,” we will fix a date for the redemption. Notice of redemption will be mailed by first class mail, postage prepaid, by us to all shareholders, including beneficial owners, not less than 30 days prior to the redemption date (the “30-day Redemption Period”) to the registered holders of the warrants to be redeemed at their last addresses as

they appear on the registration books. Any notice mailed in the manner provide above will be conclusively presumed to have been duly given whether or not the registered holder of the warrants received such notice. We are not contractually obligated to notify investors when its warrants become eligible for redemption, and does not intend to so notify investors upon eligibility of the warrants for redemption.

Beginning on the date the notice of redemption is given until the warrants are redeemed or exercised, holders may elect to exercise their warrants on a cashless basis. The numbers in the table below represent the number of shares of our Common Stock that a warrant holder will receive upon such cashless exercise in connection with a redemption by us pursuant to this redemption feature, based on the “fair market value” of our Common Stock on the corresponding redemption date (assuming holders elect to exercise their warrants and such warrants are not redeemed for $0.10 per warrant), determined for these purposes based on volume weighted average price of our Common Stock during the 10 trading days immediately following the date on which the notice of redemption is sent to the holders of warrants, and the number of months that the corresponding redemption date precedes the expiration date of the warrants, each as set forth in the table below. We will provide warrant holders with the final fair market value no later than one business day after the 10-trading day period described above ends.

The share prices set forth in the column headings of the table below will be adjusted as of any date on which the number of shares issuable upon exercise of a warrant or the exercise price of a warrant is adjusted as set forth under the heading “—Anti-dilution Adjustments” below. If the number of shares issuable upon exercise of a warrant is adjusted, the adjusted share prices in the column headings will equal the share prices immediately prior to such adjustment, multiplied by a fraction, the numerator of which is the number of shares deliverable upon exercise of a warrant immediately prior to such adjustment and the denominator of which is the number of shares deliverable upon exercise of a warrant as so adjusted. The number of shares in the table below shall be adjusted in the same manner and at the same time as the number of shares issuable upon exercise of a warrant. If the exercise price of a warrant is adjusted, (a) in the case of an adjustment pursuant to the fifth paragraph under the heading “—Anti-dilution Adjustments” below, the adjusted share prices in the column headings will equal the unadjusted share price multiplied by a fraction, the numerator of which is the higher of the Market Value and the Newly Issued Price as set forth under the heading “—Anti-dilution Adjustments” and the denominator of which is $10.00 and (b) in the case of an adjustment pursuant to the second paragraph under the heading “—Anti-dilution Adjustments” below, the

adjusted share prices in the column headings will equal the unadjusted share price less the decrease in the exercise price of a warrant pursuant to such exercise price adjustment.


Redemption Date (period to expiration of warrants)	Fair Market Value of Common Stock
	$10.00	11.00	12.00	13.00	14.00	15.00	16.00	17.00	18.00
60 months	0.261	0.281	0.297	0.311	0.324	0.337	0.348	0.358	0.361
57 months	0.257	0.277	0.294	0.310	0.324	0.337	0.348	0.358	0.361
54 months	0.252	0.272	0.291	0.307	0.322	0.335	0.347	0.357	0.361
51 months	0.246	0.268	0.287	0.304	0.320	0.333	0.346	0.357	0.361
48 months	0.241	0.263	0.283	0.301	0.317	0.332	0.344	0.356	0.361
45 months	0.235	0.258	0.279	0.298	0.315	0.330	0.343	0.356	0.361
42 months	0.228	0.252	0.274	0.294	0.312	0.328	0.342	0.355	0.361
39 months	0.221	0.246	0.269	0.290	0.309	0.325	0.340	0.354	0.361
36 months	0.213	0.239	0.263	0.285	0.305	0.323	0.339	0.353	0.361
33 months	0.205	0.232	0.257	0.280	0.301	0.320	0.337	0.352	0.361
30 months	0.196	0.224	0.250	0.274	0.297	0.316	0.335	0.351	0.361
27 months	0.185	0.214	0.242	0.268	0.291	0.313	0.332	0.350	0.361
24 months	0.173	0.204	0.233	0.260	0.285	0.308	0.329	0.348	0.361
21 months	0.161	0.193	0.223	0.252	0.279	0.304	0.326	0.347	0.361
18 months	0.146	0.179	0.211	0.242	0.271	0.298	0.322	0.345	0.361
15 months	0.130	0.164	0.197	0.230	0.262	0.291	0.317	0.342	0.361
12 months	0.111	0.146	0.181	0.216	0.250	0.282	0.312	0.339	0.361
9 months	0.090	0.125	0.162	0.199	0.237	0.272	0.305	0.336	0.361
6 months	0.065	0.099	0.137	0.178	0.219	0.259	0.296	0.331	0.361
3 months	0.034	0.065	0.104	0.150	0.197	0.243	0.286	0.326	0.361
0 months	—	—	0.042	0.115	0.179	0.233	0.281	0.323	0.361

The exact fair market value and redemption date may not be set forth in the table above, in which case, if the fair market value is between two values in the table or the redemption date is between two redemption dates in the table, the number of shares of Common Stock to be issued for each warrant exercised will be determined by a straight-line interpolation between the number of shares set forth for the higher and lower fair market values and the earlier and later redemption dates, as applicable, based on a 365 or 366-day year, as applicable. For example, if the volume weighted average price of our Common Stock during the 10 trading days immediately following the date on which the notice of redemption is sent to the holders of the warrants is $11.00 per share, and at such time there are 57 months until the expiration of the warrants, holders may choose to, in connection with this redemption feature, exercise their warrants for 0.277 shares of Common Stock for each whole warrant. For an example where the exact fair market value and redemption date are not as set forth in the table above, if the volume weighted average price of our Common Stock during the 10 trading days immediately following the date on which the notice of redemption is sent to the holders of the warrants is $13.50 per share, and at such time there are 38 months until the expiration of the warrants, holders may choose to, in connection with this redemption feature, exercise their warrants for 0.298 shares of Common Stock for each whole warrant. In no event will the warrants be exercisable on a cashless basis in connection with this redemption feature for more than 0.361 shares of Common Stock per warrant (subject to adjustment). Finally, as reflected in the table above, if the warrants are out of the money and about to expire, they cannot be exercised on a cashless basis in connection with a redemption by us pursuant to this redemption feature, since they will not be exercisable for any shares of Common Stock.

This redemption feature differs from the typical warrant redemption features used in some other blank check offerings, which only provide for a redemption of warrants for cash (other than the private placement warrants) when the trading price of our Common Stock exceeds $18.00 per share for a specified period of time. This redemption feature is structured to allow for all of the outstanding warrants to be redeemed when our Common

Stock is trading at or above $10.00 per public share, which may be at a time when the trading price of our Common Stock is below the exercise price of the warrants. We have established this redemption feature to provide it with the flexibility to redeem the warrants without the warrants having to reach the $18.00 per share threshold set forth above under “—Redemption of warrants when the price per share of our Common Stock equals or exceeds $18.00.” Holders choosing to exercise their warrants in connection with a redemption pursuant to this feature will, in effect, receive a number of shares for their warrants based on an option pricing model with a fixed volatility input as of the date of this prospectus. This redemption right provides us with an additional mechanism by which to redeem all of the outstanding warrants, and therefore have certainty as to its capital structure as the warrants would no longer be outstanding and would have been exercised or redeemed. We will be required to pay the applicable redemption price to warrant holders if we choose to exercise this redemption right and it will allow us to quickly proceed with a redemption of the warrants if we determine it is in its best interest to do so. As such, we would redeem the warrants in this manner when we believe it is in its best interest to update its capital structure to remove the warrants and pay the redemption price to the warrant holders.

As stated above, we can redeem the warrants when our Common Stock is trading at a price starting at $10.00, which is below the exercise price of $11.50, because it will provide certainty with respect to our capital structure and cash position while providing warrant holders with the opportunity to exercise their warrants on a cashless basis for the applicable number of shares. If we choose to redeem the warrants when our Common Stock is trading at a price below the exercise price of the warrants, this could result in the warrant holders receiving fewer shares of Common Stock than they would have received if they had chosen to wait to exercise their warrants for our Common Stock if and when such shares were trading at a price higher than the exercise price of $11.50.

No fractional shares of Common Stock will be issued upon exercise. If, upon exercise, a holder would be entitled to receive a fractional interest in a share, we will round down to the nearest whole number of the number of shares of Common Stock to be issued to the holder.

Redemption procedures. A holder of a warrant may notify us in writing in the event it elects to be subject to a requirement that such holder will not have the right to exercise such warrant, to the extent that after giving effect to such exercise, such person (together with such person’s affiliates), to the warrant agent’s actual knowledge, would beneficially own in excess of 9.8% (or such other amount as a holder may specify) of our Common Stock issued and outstanding immediately after giving effect to such exercise.

Anti-dilution Adjustments. If the number of outstanding shares of Common Stock is increased by a capitalization or share dividend payable in shares of Common Stock, or by a split-up of ordinary shares or other similar event, then, on the effective date of such capitalization or share dividend, split-up or similar event, the number of shares of Common Stock issuable on exercise of each warrant will be increased in proportion to such increase in the outstanding ordinary shares. A rights offering made to all or substantially all holders of ordinary shares entitling holders to purchase shares of Common Stock at a price less than the “historical fair market value” (as defined below) will be deemed a share dividend of a number of shares of Common Stock equal to the product of (i) the number of shares of Common Stock actually sold in such rights offering (or issuable under any other equity securities sold in such rights offering that are convertible into or exercisable for shares of Common Stock) and (ii) one minus the quotient of (x) the price per share of Common Stock paid in such rights offering and (y) the historical fair market value. For these purposes, (i) if the rights offering is for securities convertible into or exercisable for shares of Common Stock, in determining the price payable for shares of Common Stock there will be taken into account any consideration received for such rights, as well as any additional amount payable upon exercise or conversion and (ii) “historical fair market value” means the volume weighted average price of our Common Stock as reported during the 10 trading day period ending on the trading day prior to the first date on which the shares of Common Stock trade on the applicable exchange or in the applicable market, regular way, without the right to receive such rights.

In addition, if we, at any time while the warrants are outstanding and unexpired, pays a dividend or make a distribution in cash, securities or other assets to all or substantially all of the holders of shares of Common Stock on account of such shares (or other securities into which the warrants are convertible), other than (a) as described above, or (b) any cash dividends or cash distributions which, when combined on a per share basis with all other cash dividends and cash distributions paid on the shares of Common Stock during the 365-day period ending on the date

of declaration of such dividend or distribution does not exceed $0.50 (as adjusted to appropriately reflect any other adjustments and excluding cash dividends or cash distributions that resulted in an adjustment to the exercise price or to the number of the shares of Common Stock issuable on exercise of each warrant) but only with respect to the amount of the aggregate cash dividends or cash distributions equal to or less than $0.50 per share.

If the number of outstanding shares of Common Stock is decreased by a consolidation, combination, reverse share split or reclassification of shares of Common Stock or other similar event, then, on the effective date of such consolidation, combination, reverse share split, reclassification or similar event, the number of shares of Common Stock issuable on exercise of each warrant will be decreased in proportion to such decrease in outstanding shares of Common Stock.

Whenever the number of shares of Common Stock purchasable upon the exercise of the warrants is adjusted, as described above, the warrant exercise price will be adjusted by multiplying the warrant exercise price immediately prior to such adjustment by a fraction (x) the numerator of which will be the number of shares of Common Stock purchasable upon the exercise of the warrants immediately prior to such adjustment and (y) the denominator of which will be the number of shares of Common Stock so purchasable immediately thereafter.

In case of any reclassification or reorganization of the outstanding shares of Common Stock (other than those described above or that solely affects the par value of such shares of Common Stock), or in the case of any merger or consolidation of us with or into another corporation (other than a consolidation or merger in which we are the continuing corporation and that does not result in any reclassification or reorganization of outstanding shares of Common Stock), or in the case of any sale or conveyance to another corporation or entity of our assets or other property as an entirety or substantially as an entirety in connection with which we are dissolved, the holders of the warrants will thereafter have the right to purchase and receive, upon the basis and upon the terms and conditions specified in the warrants and in lieu of the shares of Common Stock immediately theretofore purchasable and receivable upon the exercise of the rights represented thereby, the kind and amount of shares of Common Stock or other securities or property (including cash) receivable upon such reclassification, reorganization, merger or consolidation, or upon a dissolution following any such sale or transfer, that the holder of the warrants would have received if such holder had exercised their warrants immediately prior to such event. However, if such holders were entitled to exercise a right of election as to the kind or amount of securities, cash or other assets receivable upon such consolidation or merger, then the kind and amount of securities, cash or other assets for which each warrant will become exercisable will be deemed to be the weighted average of the kind and amount received per share by such holders in such consolidation or merger that affirmatively make such election, and if a tender, exchange or redemption offer has been made to and accepted by such holders under circumstances in which, upon completion of such tender or exchange offer, the maker thereof, together with members of any group (within the meaning of Rule 13d-5(b)(1) under the Exchange Act) of which such maker is a part, and together with any affiliate or associate of such maker (within the meaning of Rule 12b-2 under the Exchange Act) and any members of any such group of which any such affiliate or associate is a part, own beneficially (within the meaning of Rule 13d-3 under the Exchange Act) more than 50% of the issued and outstanding shares of Common Stock, the holder of a warrant will be entitled to receive the highest amount of cash, securities or other property to which such holder would actually have been entitled as a shareholder if such warrant holder had exercised the warrant prior to the expiration of such tender or exchange offer, accepted such offer and all of the shares of Common Stock held by such holder had been purchased pursuant to such tender or exchange offer, subject to adjustment (from and after the consummation of such tender or exchange offer) as nearly equivalent as possible to the adjustments provided for in the warrant agreement. If less than 70% of the consideration receivable by the holders of shares of Common Stock in such a transaction is payable in the form of shares in the successor entity that is listed for trading on a national securities exchange or is quoted in an established over-the-counter market, or is to be so listed for trading or quoted immediately following such event, and if the registered holder of the warrant properly exercises the warrant within thirty days following public disclosure of such transaction, the warrant exercise price will be reduced as specified in the warrant agreement based on the Black-Scholes value (as defined in the warrant agreement) of the warrant. The purpose of such exercise price reduction is to provide additional value to holders of the warrants when an extraordinary transaction occurs during the exercise period of the warrants pursuant to which the holders of the warrants otherwise do not receive the full potential value of the warrants. The purpose of such exercise price reduction is to provide additional value to holders of the warrants when an extraordinary transaction occurs during

the exercise period of the warrants pursuant to which the holders of the warrants otherwise do not receive the full potential value of the warrants.

The warrant holders do not have the rights or privileges of holders of ordinary shares and any voting rights until they exercise their warrants and receive shares of Common Stock. After the issuance of shares of Common Stock upon exercise of the warrants, each holder will be entitled to one vote for each share held of record on all matters to be voted on by shareholders.

No fractional warrants will be issued upon separation of the units and only whole warrants will trade. If, upon exercise of the warrants, a holder would be entitled to receive a fractional interest in a share, we will, upon exercise, round down to the nearest whole number the number of shares of Common Stock to be issued to the warrant holder.

We have agreed that, subject to applicable law, any action, proceeding or claim against it arising out of or relating in any way to the Warrant Agreement will be brought and enforced in the courts of the State of New York or the United States District Court for the Southern District of New York, and we irrevocably submits to such jurisdiction, which jurisdiction will be the exclusive forum for any such action, proceeding or claim. This provision applies to claims under the Securities Act but does not apply to claims under the Exchange Act or any claim for which the federal district courts of the United States of America are the sole and exclusive forum.

Private Placement Warrants

Except as described below, the private placement warrants have terms and provisions that are identical to those of the public warrants. 3,500,000 of the private placement warrants vested on October 8, 2021 pursuant to the terms of the Sponsor Letter Agreement (the “Sponsor Letter Agreement”), dated as of May 6, 2021, by and among ACON S2 Sponsor, L.L.C., a Delaware limited liability company (the “Sponsor”), ESS, Legacy ESS, and, solely for purposes of certain sections, the Insiders (as defined in the Sponsor Letter Agreement). The remaining 583,334 of the private placement warrants vested on November 9, 2021, upon the occurrence of the earnout milestone events pursuant to the Sponsor Letter Agreement. The private placement warrants will not be redeemable by us (except as described under “—Public Warrants—Redemption of warrants when the price per share of our Common Stock equals or exceeds $10.00”) so long as they are held by the Sponsor or its permitted transferees (except as otherwise set forth herein). The Sponsor, or its permitted transferees, has the option to exercise the private placement warrants on a cashless basis. If the private placement warrants are held by holders other than the Sponsor or its permitted transferees, the private placement warrants will be redeemable by us in all redemption scenarios and exercisable by the holders on the same basis as the public warrants. Any amendment to the terms of the private placement warrants or any provision of the Warrant Agreement with respect to the private placement warrants will require a vote of holders of at least 50% of the number of the then outstanding private placement warrants.

Except as described above under “—Public Warrants—Redemption of warrants when the price per share of our Common Stock equals or exceeds $10.00,” if holders of the private placement warrants elect to exercise them on a cashless basis, they would pay the exercise price by surrendering his, her or its warrants for that number of shares of Common Stock equal to the quotient obtained by dividing (x) the product of the number of shares of Common Stock underlying the warrants, multiplied by the excess of the “Sponsor fair market value” (as defined below) over the exercise price of the warrants by (y) the Sponsor fair market value. For these purposes, the “Sponsor fair market value” shall mean the average reported closing price of the shares of Common Stock for the 10 trading days ending on the third trading day prior to the date on which the notice of warrant exercise is sent to the warrant agent.

Registration Rights

Under the Registration Rights Agreement (the “Registration Rights Agreement”), dated October 8, 2021, by and among ESS, the Sponsor and other holders of Common Stock, the holders of 73,022,199 shares of Common Stock or their permitted transferees have the right to require us to register the offer and sale of their shares, or to include their shares in any registration statement we file, in each case as described below.

Resale Registration Statement

We filed a registration statement on Form S-1 on November 2, 2021 (File No. 333-260693) (the “Initial Resale Registration Statement”), Post-Effective Amendment No. 1 to the Initial Resale Registration Statement on December 9, 2021, and a registration statement on Form S-1 and Post-Effective Amendment No. 2 to the Initial Resale Registration Statement on March 4, 2022 (File No. 333-263316) (the “Additional Resale Registration Statement” and together with the Initial Resale Registration Statement, the “Prior Registration Statements”) for an offering of our Common Stock to be made on a delayed or continuous basis. Pursuant to the Registration Rights Agreement, the holders of at least $30.0 million of shares having registration rights then outstanding can request that we effect an underwritten public offering pursuant to such Prior Registration Statements. We are only obligated to effect no more than four such registrations within any 12-month period. These registration rights are subject to specified conditions and limitations, including the right of the underwriters to limit the number of shares included in any such registration under certain circumstances.

The Additional Resale Registration Statement was declared effective by the SEC on March 16, 2022.

Pursuant to Rule 429 under the Securities Act, the post-effective amendment to the Prior Registration Statements of which this prospectus forms a part was filed with the SEC (i) to convert the Prior Registration Statements on Form S-1 into a registration statement on Form S-3 and (ii) to update certain other information.

Piggyback Registration Rights

If we propose to register the offer and sale of our Common Stock under the Securities Act, all holders of these shares then outstanding can request that we include their shares in such registration, subject to certain marketing and other limitations, including the right of the underwriters to limit the number of shares included in any such registration statement under certain circumstances. As a result, whenever we propose to file a registration statement under the Securities Act, other than with respect to a registration (i) relating to any employee stock option or other benefit plan, (ii) on Form S-4 (or similar form that relates to a transaction subject to Rule 145 under the Securities Act or any successor rule thereto), (iii) relating to an offering of debt that is convertible into equity securities of ESS, or (iv) for a dividend reinvestment plan.

Termination

The registration rights terminate upon the date as of which all of the registrable securities have been sold pursuant to a registration statement or are permitted to be sold under Rule 144 or any similar provision under the Securities Act.

Registration Rights for PIPE Shares

On May 6, 2021, STWO entered into subscription agreements with certain investors, pursuant to which STWO agreed to issue and sell to the investors 25,000,000 shares of Common Stock (“PIPE Shares”) at a purchase price of $10.00 per share for an aggregate commitment of $250,000,000 (the “PIPE Financing”). The PIPE Financing was consummated on October 8, 2021. The Prior Registration Statements also registered the PIPE Shares for resale.

Form S-8 Registration Statement

We filed a registration statement on Form S-8 under the Securities Act to register the shares of Common Stock issued or issuable under our 2021 Employee Stock Purchase Plan, 2021 Equity Incentive Plan and 2014 Equity Incentive Plan. The Form S-8 registration statement became effective automatically upon filing, and shares covered by the registration statement became eligible for sale in the public market, subject to Rule 144 limitations applicable to affiliates and vesting restrictions.

Limitation of Liability and Indemnification

Our certificate of incorporation contains provisions that limit the liability of our directors for monetary damages to the fullest extent permitted by the DGCL. In addition, if the DGCL is amended to authorize corporate action

further eliminating or limiting the personal liability of directors of corporations, then the personal liability of our directors will be eliminated or limited to the greatest extent permitted by the DGCL.

In addition, our bylaws, which became effective upon consummation of the Merger, provides that we will indemnify our directors and officers to the fullest extent permitted by the DGCL and we may indemnify our employees, agents and any other persons to the extent not prohibited by the DGCL or other applicable law. Our amended and restated bylaws will also provide that we must advance expenses incurred by or on behalf of a director or officer in advance of the final disposition of any action or proceeding, subject to limited exceptions.

Further, we have entered into indemnification agreements with our directors and executive officers that are broader than the specific indemnification provisions contained in the DGCL and may continue to do so in the future. These indemnification agreements require us to indemnify our directors and executive officers against liabilities that may arise by reason of their status or service. These indemnification agreements also require us to advance all expenses reasonably and actually incurred by our directors and executive officers in investigating or defending any such action, suit or proceeding. We believe that these agreements are necessary to attract and retain qualified individuals to serve as directors and executive officers.

We also maintain insurance policies under which our directors and officers are insured, within the limits and subject to the limitations of those policies, against certain expenses in connection with the defense of, and certain liabilities which might be imposed as a result of, actions, suits, or proceedings to which they are parties by reason of being or having served as a director or officer of ESS. At present, we are not aware of any pending litigation or proceeding involving any person who is one of our directors or officers or is or was one of our directors or officers, or is or was one of our directors or officers serving at our request as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, for which indemnification is sought, and we are not aware of any threatened litigation that may result in claims for indemnification.

Description of Certain Terms in the Charter Documents and Delaware Law

The certificate of incorporation and amended and restated bylaws contain provisions that could have the effect of delaying, deferring or discouraging another party from acquiring control of ESS. These provisions and certain provisions of Delaware law, which are summarized below, could discourage takeovers, coercive or otherwise. These provisions are also designed, in part, to encourage persons seeking to acquire control of ESS to negotiate first with our board of directors. ESS believes that the benefits of increased protection of the potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire the Company.

Issuance of Undesignated Preferred Stock. As discussed above under “—Preferred Stock,” our board of directors has the ability to designate and issue preferred stock with voting or other rights or preferences that could deter hostile takeovers or delay changes in control or management.

Limits on Ability of Stockholders to Act by Written Consent or Call a Special Meeting. The certificate of incorporation provides that the stockholders may not act by written consent. This limit on the ability of stockholders to act by written consent may lengthen the amount of time required to take stockholder actions. As a result, the holders of a majority of our capital stock may not be able to amend the amended and restated bylaws or remove directors without holding a meeting of stockholders called in accordance with the amended and restated bylaws.

In addition, the amended and restated bylaws provide that special meetings of the stockholders may be called only by the chairperson of the board of directors, the chief executive officer, the president, or a majority of our board of directors (measured based on the total authorized directorships, including any vacancies or unfilled seats). A stockholder may not call a special meeting, which may delay the ability of the stockholders to force consideration of a proposal or for holders controlling a majority of our capital stock to take any action, including the removal of directors.

Requirements for Advance Notification of Stockholder Nominations and Proposals. The amended and restated bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of our board of directors or a committee

of our board of directors. These advance notice procedures may have the effect of precluding the conduct of certain business at a meeting if the proper procedures are not followed and may also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect its own slate of directors or otherwise attempt to obtain control of ESS.

Board Classification. The certificate of incorporation provides that our board of directors is divided into three classes, one class of which is elected each year by the stockholders. The directors in each class will serve for a three-year term. The classified board of directors may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of ESS because it generally makes it more difficult for stockholders to replace a majority of the directors.

Election and Removal of Directors. The certificate of incorporation contains provisions that establish specific procedures for appointing and removing members of our board of directors. Under the certificate of incorporation and amended and restated bylaws, vacancies and newly created directorships on our board of directors may be filled only by a majority of the directors then serving on our board of directors. Under the certificate of incorporation, directors may be removed only for cause by the affirmative vote of the holders of at least a majority of the voting power of the issued and outstanding capital stock of the Company entitled to vote in the election of directors.

No Cumulative Voting. The DGCL provides that stockholders are not entitled to the right to cumulate votes in the election of directors unless a corporation’s certificate of incorporation provides otherwise. The certificate of incorporation and amended and restated bylaws do not expressly provide for cumulative voting. Without cumulative voting, a minority stockholder may not be able to gain as many seats on the board of directors as the stockholder would be able to gain if cumulative voting were permitted. The absence of cumulative voting makes it more difficult for a minority stockholder to gain a seat on the board of directors to, among other things, influence the board of directors’ decision regarding a takeover.

Amendment of Charter Provision. Any amendment of the above provisions in the certificate of incorporation or amended and restated bylaws would require approval by holders of at least 662/3% of the then outstanding capital stock entitled to vote, voting together as a single class.

Delaware Anti-Takeover Statute. ESS is subject to the provisions of Section 203 of the DGCL regulating corporate takeovers. In general, Section 203 prohibits a publicly held Delaware corporation from engaging, under certain circumstances, in a business combination with an interested stockholder for a period of three years following the date the person became an interested stockholder unless:

•prior to the date of the transaction, the board of directors approved either the business combination or the transaction that resulted in the stockholder becoming an interested stockholder;

•upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the voting stock outstanding, but not the outstanding voting stock owned by the interested stockholder, (1) shares owned by persons who are directors and also officers and (2) shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

•at or subsequent to the date of the transaction, the business combination is approved by the board of directors and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting stock that is not owned by the interested stockholder.

Generally, a business combination includes a merger, asset or stock sale or other transaction resulting in a financial benefit to the interested stockholder. An interested stockholder is generally defined under Section 203 to be a person who, together with affiliates and associates, owns or, within three years prior to the determination of interested stockholder status, did own 15% or more of a corporation’s outstanding voting stock. ESS expects the existence of this provision to have an anti-takeover effect with respect to transactions our board of directors does not

approve in advance. We also anticipate that Section 203 may discourage attempts that might result in a premium over the market price for the shares of Common Stock held by stockholders.

The provisions of Delaware law and the provisions of the certificate of incorporation and amended and restated bylaws could have the effect of discouraging others from attempting hostile takeovers and as a consequence, they might also inhibit temporary fluctuations in the market price of our Common Stock that often result from actual or rumored hostile takeover attempts. These provisions might also have the effect of preventing changes in management. It is also possible that these provisions could make it more difficult to accomplish transactions that stockholders might otherwise deem to be in their best interests.

Choice of Forum. The amended and restated bylaws provides that the Court of Chancery of the State of Delaware will be the exclusive forum for: (i) any derivative action or proceeding brought on ESS’ behalf; (ii) actions asserting a breach of fiduciary duty; (iii) any action arising under the DGCL, the certificate of incorporation or amended and restated bylaws; and (iv) any action asserting a claim against ESS that is governed by the internal-affairs doctrine. The amended and restated bylaws further provide that the federal district courts of the United States will be the exclusive forum for resolving any complaint asserting a cause of action arising under the Securities Act.

Transfer Agent

The transfer agent and warrant agent for the Common Stock is Computershare Inc. The transfer agent’s address is 150 Royall Street, Canton, MA 02021 and its telephone number is (206) 406-5789.

PLAN OF DISTRIBUTION

We have previously registered up to 130,044,756 shares of our Common Stock on the Prior Registration Statements, for resale by the Selling Stockholders. As used herein, references to “Selling Stockholders” includes donees, pledgees, transferees, distributees or other successors-in-interest selling shares of Common Stock or interests in the securities received after the date of this prospectus from a Selling Stockholder as a gift, pledge, partnership distribution or other transfer.

We will not receive any of the proceeds of the sale of the securities offered by this prospectus. The aggregate proceeds to the Selling Stockholders from the sale of the securities will be the purchase price of the securities less any discounts and commissions. We will not pay any brokers’ or underwriters’ discounts and commissions in connection with the registration and sale of the securities covered by this prospectus. The Selling Stockholders reserve the right to accept and, together with their respective agents, to reject, any proposed purchases of securities to be made directly or through agents.

The securities offered by this prospectus may be sold from time to time to purchasers:

•directly by the Selling Stockholders;

•through underwriters, broker-dealers or agents, who may receive compensation in the form of discounts, commissions or agent’s commissions from the Selling Stockholders or the purchasers of the securities; or

•through a combination of any of these methods of sale.

Any underwriters, broker-dealers or agents who participate in the sale or distribution of the securities may be deemed to be “underwriters” within the meaning of the Securities Act. As a result, any discounts, commissions or concessions received by any such broker-dealer or agents who are deemed to be underwriters will be deemed to be underwriting discounts and commissions under the Securities Act. Underwriters are subject to the prospectus delivery requirements of the Securities Act and may be subject to certain statutory liabilities under the Securities Act and the Exchange Act. We will make copies of this prospectus available to the Selling Stockholders for the purpose of satisfying the prospectus delivery requirements of the Securities Act. To our knowledge, there are currently no plans, arrangements or understandings between the Selling Stockholders and any underwriter, broker-dealer or agent regarding the sale of the securities by the Selling Stockholders.

The securities may be sold in one or more transactions at:

•fixed prices;

•prevailing market prices at the time of sale;

•prices related to such prevailing market prices;

•varying prices determined at the time of sale; or

•negotiated prices.

These sales may be effected in one or more transactions:

•through one or more underwritten offerings on a firm commitment or best efforts basis;

•settlement of short sales entered into after the date of this prospectus;

•agreements with broker-dealers to sell a specified number of the securities at a stipulated price per share;

•in “at the market” offerings, as defined in Rule 415 under the Securities Act, at negotiated prices, at prices prevailing at the time of sale or at prices related to such prevailing market prices, including sales made directly on a national securities exchange or sales made through a market maker other than on an exchange or other similar offerings through sales agents;

•in privately negotiated transactions;

•in options or other hedging transactions, whether through an options exchange or otherwise;

•in distributions to members, limited partners or stockholders of Selling Stockholders;

•any other method permitted by applicable law;

•on any national securities exchange or quotation service on which the securities may be listed or quoted at the time of sale, including the NYSE;

•in the over-the-counter market;

•in transactions otherwise than on such exchanges or services or in the over-the-counter market;

•any other method permitted by applicable law; or

•through any combination of the foregoing.

These transactions may include block transactions or crosses. Crosses are transactions in which the same broker acts as an agent on both sides of the trade.

In connection with distributions of the securities or otherwise, the Selling Stockholders may enter into hedging transactions with broker-dealers or other financial institutions. In connection with such transactions, broker-dealers or other financial institutions may engage in short sales of the securities in the course of hedging transactions, broker-dealers or other financial institutions may engage in short sales of the securities in the course of hedging the positions they assume with Selling Stockholders. The Selling Stockholders may also sell the securities short and redeliver the securities to close out such short positions. The Selling Stockholders may also enter into option or other transactions with broker-dealers or other financial institutions which require the delivery to such broker-dealer or other financial institution of the securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction). The Selling Stockholders may also pledge the securities to a broker-dealer or other financial institution, and, upon a default, such broker-dealer or other financial institution, may effect sales of the pledged securities pursuant to this prospectus (as supplemented or amended to reflect such transaction).

A Selling Stockholder may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell the securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by any Selling Stockholder or borrowed from any Selling Stockholder or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from any Selling Stockholder in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement (or a post-effective amendment). In addition, any Selling Stockholder may otherwise loan or pledge the securities to a financial institution or other third party that in turn may sell the securities short using this prospectus. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

At the time a particular offering of the securities is made, a prospectus supplement, if required, will be distributed, which will set forth the name of the Selling Stockholders, the aggregate amount of securities being offered and the terms of the offering, including, to the extent required, (1) the name or names of any underwriters, broker-dealers or agents, (2) any discounts, commissions and other terms constituting compensation from the Selling Stockholders and (3) any discounts, commissions or concessions allowed or reallowed to be paid to broker-dealers. We may suspend the sale of securities by the Selling Stockholders pursuant to this prospectus for certain periods of time for certain reasons, including if the prospectus is required to be supplemented or amended to include additional material information, and we may file a post-effective amendment to the registration statement of which this

prospectus is a part to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement.

The Selling Stockholders also may transfer the securities in other circumstances, in which case the transferees, pledgees or other successors-in-interest will be the selling beneficial owners for purposes of this prospectus. Upon being notified by a Selling Stockholder that a donee, pledgee, transferee, other successor-in-interest intends to sell our securities, we will, to the extent required, promptly file a supplement to this prospectus to name specifically such person as a Selling Stockholder.

The Selling Stockholders will act independently of us in making decisions with respect to the timing, manner, and size of each resale or other transfer. There can be no assurance that the Selling Stockholders will sell any or all of the securities under this prospectus. Further, we cannot assure you that the Selling Stockholders will not transfer, distribute, devise or gift the securities by other means not described in this prospectus. In addition, any securities covered by this prospectus that qualify for sale under Rule 144 of the Securities Act may be sold under Rule 144 rather than under this prospectus. The securities may be sold in some states only through registered or licensed brokers or dealers. In addition, in some states the securities may not be sold unless they have been registered or qualified for sale or an exemption from registration or qualification is available and complied with.

The Selling Stockholders may, from time to time, pledge or grant a security interest in some shares of the securities owned by them and, if a Selling Stockholder defaults in the performance of its secured obligations, the pledgees or secured parties may offer and sell such shares of the securities, from time to time, under this prospectus, or under an amendment or supplement to this prospectus amending the list of the Selling Stockholders to include the pledgee, transferee or other successors in interest as the Selling Stockholders under this prospectus. The Selling Stockholders also may transfer shares of the securities in other circumstances, in which case the transferees, pledgees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

A Selling Stockholder that is an entity may elect to make an in-kind distribution of the securities to its members, partners or shareholders pursuant to the registration statement of which this prospectus is a part by delivering a prospectus. To the extent that such members, partners or shareholders are not affiliates of ours, such members, partners or stockholders would thereby receive freely tradable shares of the securities pursuant to the distribution through a registration statement.

A Selling Stockholder that is an entity may elect to make an in-kind distribution of the securities to its members, partners or shareholders pursuant to this prospectus is a part by delivering a prospectus. To the extent that such members, partners or shareholders are not affiliates of ours, such members, partners or stockholders would thereby receive freely tradable shares of the securities pursuant to the distribution through this prospectus.

For additional information regarding expenses of registration, see the section titled “Use of Proceeds” appearing elsewhere in this prospectus.

LEGAL MATTERS

The validity of the Common Stock being offered hereby will be passed upon for us by Wilson Sonsini Goodrich & Rosati, Professional Corporation, Palo Alto, California. Additional legal matters may be passed on for us, or any underwriters, dealers or agents by counsel we may name in a prospectus supplement.

EXPERTS

The consolidated financial statements of ESS Tech, Inc. appearing in ESS Tech, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2021, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at www.sec.gov. Copies of certain information filed by us with the SEC are also available on our website at https://essinc.com/. Information accessible on or through our website is not a part of this prospectus.

This prospectus and any prospectus supplement is part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. You should review the information and exhibits in the registration statement for further information on us and our consolidated subsidiaries and the securities that we are offering. Forms of any indenture or other documents establishing the terms of the offered securities are filed as exhibits to the registration statement of which this prospectus forms a part or under cover of a Current Report on Form 8-K and incorporated in this prospectus by reference. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should read the actual documents for a more complete description of the relevant matters.

INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference much of the information that we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated by reference in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus incorporates by reference the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those documents or the portions of those documents furnished pursuant to Items 2.02 or 7.01 of any Current Report on Form 8-K and, except as may be noted in any such Form 8-K, exhibits filed on such form that are related to such information), until the offering of the securities under the registration statement of which this prospectus forms a part is terminated or completed:

•our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 4, 2022;

•our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2022, June 30, 2022 and September 30, 2022, filed with the SEC on May 13, 2022, August 12, 2022 and November 3, 2022, respectively;

•the portions of our Definitive Proxy Statement on Schedule 14A (other than information furnished rather than filed) that are incorporated by reference into our Annual Report on Form 10-K, filed with the SEC on April 22, 2022;

•our Current Reports on Form 8-K filed on February 17, 2022, March 30, 2022, June 2, 2022, August 26, 2022 and October 24, 2022; and

•The description of our Common Stock contained in the Registration Statement on Form 8-A relating thereto, filed on October 8, 2021, including any amendment or report filed for the purpose of updating such description.

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address:

ESS Tech, Inc.

26440 SW Parkway Ave., Bldg. 83

Wilsonville, Oregon 97070

Attn: Investor Relations

(855) 423-9920

130,044,756 Shares of Common Stock

PROSPECTUS

, 2022

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth all expenses to be paid by us in connection with the distribution of the shares of Common Stock being registered by this registration statement. All amounts shown are estimates except for the SEC registration fee.

We will bear all costs, expenses and fees in connection with the registration of the securities. The Selling Stockholders, however, will bear all brokers and underwriting commissions and discounts, if any, attributable to the sale of their securities.


			Amount to be Paid
SEC registration fee			$ 193,668*
Accounting fees and expenses			**
Legal fees and expenses			**
Financial printing and miscellaneous expenses			**
Total			$ **

__________________

*Registration fees of $192,067 and $1,601 were previously paid in connection with the Prior Registration Statements relating to the securities that are included in this registration statement in accordance with Rule 429 under the Securities Act. Accordingly, there is no registration fee due in connection with the registration of such securities hereby.

**Omitted because estimates are not currently available. The expenses of any offering will be set forth in the applicable prospectus supplement.

Item 15. Indemnification of Directors and Officers

Section 102(b)(7) of the DGCL allows a corporation to provide in its certificate of incorporation that a director of the corporation will not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except where the director breached the duty of loyalty, failed to act in good faith, engaged in intentional misconduct or knowingly violated a law, authorized the payment of a dividend or approved a stock repurchase in violation of Delaware corporate law or obtained an improper personal benefit. Our certificate of incorporation provides for this limitation of liability.

Section 145 of the DGCL, provides, among other things, that a Delaware corporation may indemnify any person who was, is or is threatened to be made, party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person is or was an officer, director, employee or agent of such corporation or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe that his or her conduct was unlawful. A Delaware corporation may indemnify any persons who were or are a party to any threatened, pending or completed action or suit by or in the right of the corporation by reason of the fact that such person is or was a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit, provided such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests, provided further that no indemnification is permitted without judicial approval if the officer, director, employee or agent is adjudged to be liable to the corporation. Where an officer or director is successful on the merits or otherwise in the defense of any action referred to above, the corporation must indemnify him or her against the expenses (including attorneys’ fees) which such officer or director has actually and reasonably incurred.

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Section 145 further authorizes a corporation to purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or enterprise, against any liability asserted against such person and incurred by such person in any such capacity, or arising out of his or her status as such, whether or not the corporation would otherwise have the power to indemnify such person under Section 145.

Our amended and restated bylaws provide that we must indemnify and advance expenses to our directors and officers to the full extent authorized by the DGCL.

We have entered into indemnification agreements with each of our directors and executive officers. Such agreements may require us, among other things, to advance expenses and otherwise indemnify our executive officers and directors against certain liabilities that may arise by reason of their status or service as executive officers or directors, to the fullest extent permitted by law.

The indemnification rights set forth above shall not be exclusive of any other right which an indemnified person may have or hereafter acquire under any statute, any provision of our certificate of incorporation, amended and restated bylaws, agreement, vote of stockholders or disinterested directors or otherwise. Notwithstanding the foregoing, we shall not be obligated to indemnify a director or officer in respect of a proceeding (or part thereof) instituted by such director or officer, unless such proceeding (or part thereof) has been authorized by the Board pursuant to the applicable procedure outlined in our amended and restated bylaws.

Section 174 of the DGCL provides, among other things, that a director, who willfully or negligently approves of an unlawful payment of dividends or an unlawful stock purchase or redemption, may be held jointly and severally liable for such actions. A director who was either absent when the unlawful actions were approved or dissented at the time may avoid liability by causing his or her dissent to such actions to be entered in the books containing the minutes of the meetings of the Board at the time such action occurred or immediately after such absent director receives notice of the unlawful acts.

We currently maintain and expect to continue to maintain standard policies of insurance that provide coverage (1) to our directors and officers against loss rising from claims made by reason of breach of duty or other wrongful act and (2) to us with respect to indemnification payments that we may make to such directors and officers.

These provisions may discourage stockholders from bringing a lawsuit against our directors for breach of their fiduciary duty. These provisions also may have the effect of reducing the likelihood of derivative litigation against directors and officers, even though such an action, if successful, might otherwise benefit us and our stockholders. Furthermore, a stockholder’s investment may be adversely affected to the extent we pay the costs of settlement and damage awards against officers and directors pursuant to these indemnification provisions.

We believe that these provisions, the insurance, and the indemnity agreements are necessary to attract and retain talented and experienced officers and directors.

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Item 16. Exhibits

(a)Exhibits.


		Incorporation by Reference
Exhibit Number	Exhibit Description	Form	File No.	Exhibit Number	Filing Date	Filed Herewith
2.1#	Merger Agreement, dated as of May 6, 2021, by and among STWO, SCharge Merger Sub, Inc. and ESS Tech, Inc.	8-K	001-39525	2.1	May 7, 2021
3.1	Certificate of Incorporation	8-K	001-39525	3.1	October 15, 2021
3.2	Amended and Restated Bylaws	10-Q	001-39525	3.2	November 3, 2022
5.1	Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation	S-1	333-260693	5.1	November 3, 2021
5.2	Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation	S-1	333-263316	5.1	March 4, 2022
23.1	Consent of Independent Registered Public Accounting Firm					X
23.2	Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (included in the opinion filed as Exhibit 5.1 to this Registration Statement)	S-1	333-260693	5.1	November 3, 2021
23.3	Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (included in the opinion filed as Exhibit 5.2 to this Registration Statement)	S-1	333-263316	5.1	March 4, 2022
24.1	Power of Attorney (included on the signature page of the Additional Resale Registration Statements)	S-1	333-263316	24.1	March 4, 2022	X
107	Filing Fee Table	S-1	333-263316 333-260693	107	March 4, 2022

__________________

# Portions of this exhibit have been omitted in accordance with Item 601 of Regulation S-K.

(b)Calculation of Filing Fees Table.

The Calculation of Filing Fees Table filed as Exhibit 107 to the Prior Registration Statement filed on March 4, 2022 is incorporated herein by reference. No additional securities are being registered under this Post-Effective Amendment and all applicable registration fees were paid at the time of the filing of the Prior Registration Statements on November 3, 2021 and March 4, 2022, respectively. Accordingly, no changes to the Calculation of Filing Fees Table are necessary.

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Item 17. Undertakings

(a)The undersigned registrant hereby undertakes:

(1)to file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i)to include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii)to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC, pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii)to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that paragraphs (1)(i), (1)(ii) and (1)(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2)that, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3)to remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4)that, for the purpose of determining liability under the Securities Act to any purchaser:

(i)each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii)each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii) or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by

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reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5)that, for the purpose of determining liability of a registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of such undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i)any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii)any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii)the portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv)any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6)that, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(7)to file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Commission under Section 305(b)(2) of the Trust Indenture Act.

(b)Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

(c)The undersigned registrant hereby undertakes that:

(1)For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

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(2)For the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Wilsonville, State of Oregon, on November 3, 2022.


ESS TECH, INC.

By:			/s/ Eric P. Dresselhuys
			Eric P. Dresselhuys
			Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated:

Signature

Title

Date

/s/ Eric P. Dresselhuys

Chief Executive Officer and Director
(Principal Executive Officer)

November 3, 2022

Eric P. Dresselhuys

/s/ Amir Moftakhar

Chief Financial Officer
(Principal Financial and Accounting Officer)

November 3, 2022

Amir Moftakhar

Chairman of the Board

November 3, 2022

Michael R. Niggli

Director

November 3, 2022

Craig Evans

Director

November 3, 2022

Raffi Garabedian

Director

November 3, 2022

Claudia Gast

Director

November 3, 2022

Rich Hossfeld

Director

November 3, 2022

Kyle Teamey

Director

November 3, 2022

Alexi Wellman

Director

November 3, 2022

Daryl Wilson


*By:						/s/ Eric P. Dresselhuys
						Eric P. Dresselhuys
						Attorney-in-fact

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