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ESS Tech

GWH on NYSE. Market value $5m.

Watch this stockFree. We tell you when something changes.

Should I look at this?

Look carefully before going further

Why it could be worth it

Nothing stands out yet.

What to watch out for

Read the warning sign in its own filings

This is not advice.

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Who owns it

None of the long-term investors we follow own it. 46 funds in all.

Jun '25
Dec '25
Jun '26
Largest holders overall

From 13F filings for the quarter ended 30 June 2026.

Big holders and activists

3 investors own more than 5%.

  • at least 20.2%
    (filed with 3 related holders)
    Since 23 August 2024
  • Ayrton Capital LLC
    Passive investor
    at least 8.1%−1.9 pts
    (filed with 2 related holders)
    Since 30 June 2026
  • at least 4.8%−0.4 pts
    (filed with 2 related holders)
    Since 30 June 2026

From Schedule 13D and 13G filings: anyone owning more than 5% must file one.

What insiders did

In the last 12 months, 1 insider bought $25,750 of shares on the open market. 2 sold $16,612.

  • Suhadolnik Kate Eileen
    Chief Financial Officer
    Sold
    Date
    21 August 2026
    Shares
    3,927
    Price
    $0.40
    Value
    $1,579
  • Goodman Kelly F.
    SEE REMARKS
    Sold
    Date
    21 August 2026
    Shares
    5,400
    Price
    $0.40
    Value
    $2,172
  • Buckley Drew P
    CEO, Director
    Bought
    Date
    4 June 2026
    Shares
    25,000
    Price
    $1.03
    Value
    $25,750
  • Suhadolnik Kate Eileen
    Chief Financial Officer
    Sold
    Date
    22 May 2026
    Shares
    1,922
    Price
    $0.93
    Value
    $1,787
  • Goodman Kelly F.
    SEE REMARKS
    Sold
    Date
    22 May 2026
    Shares
    2,751
    Price
    $0.93
    Value
    $2,558
  • Suhadolnik Kate Eileen
    Chief Financial Officer
    Sold
    Date
    21 May 2026
    Shares
    1,735
    Price
    $0.92
    Value
    $1,596
  • Goodman Kelly F.
    SEE REMARKS
    Sold
    Date
    21 May 2026
    Shares
    2,482
    Price
    $0.92
    Value
    $2,283
  • Suhadolnik Kate Eileen
    Chief Financial Officer
    Sold
    Date
    20 February 2026
    Shares
    741
    Price
    $1.54
    Value
    $1,141
  • Goodman Kelly F.
    SEE REMARKS
    Sold
    Date
    20 February 2026
    Shares
    2,269
    Price
    $1.54
    Value
    $3,494

From Form 4 filings: insiders must report trades in their own company's shares within two days.

Warning signs in its filings

Problems the company itself reported to the SEC, in its own words.

1 serious warning sign in ESS Tech’s filings.

We look for five warning signs: doubt it can keep going, weak checks on its own accounts, a notice that its past accounts can't be relied on, a change of auditor, and one customer bringing in a big share of sales. We don't check lawsuits, investigations or debt yet.

We couldn't fully read the 10-K filed 5 Mar 2026, so we can't say there are no warning signs.

  • Doubt it can keep going

    Serious

    The company or its auditor warned it may not have enough money to last the next year.

    “These uncertainties cause substantial doubt to exist as to the Company’s ability to continue as a going concern for 12 months from the issuance of these financial statements.”
    Show the full paragraph
    The continuation of the Company as a going concern is dependent upon its ability to obtain additional debt or equity financing in the near term in order to meet its near-term operating cash flow requirements and to generate profit from its operations. Management is evaluating various strategies to obtain additional funding, which may include additional offerings of equity, issuance of debt, or other capital sources. There is no assurance that the Company will be able to generate sufficient profits or obtain such financings on acceptable terms and conditions, on the timeline required, or at all. Any such financing activities are subject to market conditions and accordingly involve factors that are outside the Company’s control. If the Company is unable to raise sufficient capital in the near term, or if financing terms are not desirable, it will not have sufficient cash and liquidity to finance its business operations and make required payments. As a result, the Company may be required to delay, reduce the scope of, limit, curtail or terminate its business activities and product development, or may be forced to cease operations, liquidate assets, or seek protection under Chapters 7 or 11 of the United States Bankruptcy Code. These uncertainties cause substantial doubt to exist as to the Company’s ability to continue as a going concern for 12 months from the issuance of these financial statements. The accompanying condensed consolidated financial statements have been prepared on a going concern basis, which

    From the 10-Q filed 11 August 2026, Part I, Item 1. Financial Statements. Read it in the filing

A 10-K is the yearly report every US company files with the SEC. An 8-K is a short notice of a big event.

The deep dive

Everything above is arithmetic on public filings. The deep dive reads the last ten years of annual reports, the proxy statements, and the earnings calls, then argues the case the way Buffett, Klarman, and Hohn would, and checks every claim against the source.

  • What the business is worth, as a range, and the margin of safety at today’s price
  • Prices to start buying, buy, and buy hard
  • The three things that would make this a mistake
  • Every number footnoted to the filing it came from
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What a finished deep dive looks like

Not advice. Numbers on this page come from SEC filings and are updated each night; prices are updated again after the US market closes. The five-year figures are rounded.