ESS Tech (NYSE: GWH) revises Yorkville note terms, shifts $10M tranche to Feb 28, 2026

Rhea-AI Filing Summary

ESS Tech, Inc. entered into a second amendment to its existing promissory note with YA II PN, LTD., an investment fund managed by Yorkville Advisors Global. The amendment moves the date for the second tranche payment of $10 million (less the applicable discount) from December 12, 2025 to February 28, 2026, giving more time before this financing becomes available. It also tightens a key condition: for the second tranche to be funded, the principal amount outstanding under Tranche One must now be equal to or less than $7,000,000, reduced from the prior $20,000,000 threshold. This change links access to the additional capital more closely to how much of the first tranche has been repaid or converted.

Insights

Capital structure and financing analyst

ESS Tech tightened conditions and delayed timing on a planned $10M note tranche.

The amendment to the Yorkville-managed note keeps total committed funding intact but pushes the second $10 million tranche from December 12, 2025 to February 28, 2026. This means potential cash inflow from that tranche arrives later, which can matter if the company was planning on those funds for operations or growth initiatives.

The change in the Tranche One condition from a $20,000,000 maximum outstanding principal to $7,000,000 makes access to the second tranche more dependent on reducing the first tranche balance. That can influence how the company manages repayments or conversions under Tranche One. The overall effect on liquidity and dilution depends on how quickly Tranche One is brought down to or below the new $7,000,000 threshold.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): December 4, 2025

ESS TECH, INC.

(Exact Name of Registrant as Specified in Charter)

Delaware

001-39525

98-1550150

(State or other jurisdiction of incorporation)

(Commission File Number)

(I.R.S. Employer Identification Number)

26440 SW Parkway Ave., Bldg. 83 Wilsonville, Oregon						97070
(Address of principal executive offices)						(Zip code)

(855) 423-9920

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Stock, $0.0001 par value per share

GWH

The New York Stock Exchange

Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $11.50

GWH.W

The New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2).

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 13(a) of the Exchange Act. ☐

Item 1.01     Entry into a Material Definitive Agreement.

On December 4, 2025, ESS Tech, Inc. (the “Company”) and YA II PN, LTD., an investment fund managed by Yorkville Advisors Global, L.P. (“Yorkville”), entered into Amendment No. 2 (the “Note Amendment”) to the promissory note, originally issued on October 14, 2025, and as amended on October 31, 2025 (the “First Note Amendment”), by and between the Company and Yorkville (the “Note”). Capitalized terms used but not otherwise defined herein shall have the meanings ascribed thereto in the Note. The Note Amendment revised the Second Tranche Date from December 12, 2025 to February 28, 2026, extending the deadline by which Yorkville shall pay the Company the second tranche of $10 million less the applicable discount. In addition, the Note Amendment provides that the principal amount outstanding under Tranche One must be equal to or less than $7,000,000 instead of $20,000,000 for the second tranche to be paid. For more information on the Note and the First Note Amendment, please refer to our Current Report on Form 8-K, filed with the Securities and Exchange Commission (the “SEC”) on October 14, 2025, and our Quarterly Report on Form 10-Q, filed with the SEC on November 13, 2025.

The foregoing summary of the terms and conditions of the Note Amendment is qualified in its entirety by reference to the full text of the Note Amendment, a copy of which is filed as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01     Financial Statements and Exhibits.

(d)    Exhibits.

Exhibit No.
10.1						Note Amendment, dated December 4, 2025
104						Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized.

Dated: December 5, 2025

ESS TECH, INC.
By:			/s/ Kate Suhadolnik
Name:			Kate Suhadolnik
Title:			Interim Chief Financial Officer

FAQ

What did ESS Tech (GWH) change in its financing agreement with Yorkville?

ESS Tech entered into Amendment No. 2 to its promissory note with YA II PN, LTD., shifting the second tranche date and tightening the condition tied to Tranche One’s outstanding principal.

How much is the second tranche under ESS Techs note with Yorkville?

The second tranche under the promissory note is for $10 million, less the applicable discount, subject to the amended conditions being satisfied.

What new condition must ESS Tech meet to receive the $10 million second tranche?

For the second tranche to be paid, the principal amount outstanding under Tranche One must be equal to or less than $7,000,000, reduced from the prior $20,000,000 threshold.

When was the second tranche date changed to for ESS Techs note?

The second tranche date was revised from December 12, 2025 to February 28, 2026 under the new amendment.

Who is the counterparty to ESS Techs amended promissory note?

The promissory note and its amendments are between ESS Tech, Inc. and YA II PN, LTD., an investment fund managed by Yorkville Advisors Global, L.P..

Where can investors find the full text of ESS Techs note amendment?

The full Note Amendment is filed as Exhibit 10.1 to the current report and is incorporated by reference.