COMPANY PROFILE / NEXT-GEN ENERGY STORAGE
ESS Tech
A U.S. company that began with long-duration iron flow batteries and is now widening to sodium-ion: substantial doubt about its ability to continue as a going concern has been disclosed, and the New York Stock Exchange suspended trading in its shares in October 2026
ESS Tech comes up in any discussion of next-generation storage because it is one of the few listed companies that has tried to commercialize the "iron flow battery", which uses a water-based electrolyte of iron, salt and water, as a long-duration storage product. Its annual report (Form 10-K) for the year ended 31 December 2025, filed on 5 March 2026, shows revenue of US$1.58 million (US$6.3 million a year earlier), a gross loss of US$27.7 million and a net loss of about US$63.4 million, and it states that "there is substantial doubt" about the company's ability to continue as a going concern. From April 2026 the company announced a widening of its business to sodium-ion batteries (with cells bought from third parties), and on 2 October 2026 the New York Stock Exchange (NYSE) began delisting proceedings and suspended trading. This profile follows the 10-K, 10-Q, 8-Ks and other disclosures as written, setting out what the company has put into next-generation storage, what has happened, and what cannot be confirmed, in a neutral way. It is not an assessment of the company's financial condition or technology.
- ESS Tech in 30 seconds, and where it stands in next-generation storage
- The logo and how the name is written
- Where the company sits in the field
- Scale
- Resources committed to next-generation storage
- What it has done so far
- What comes next
- What the company is aiming for in next-generation storage
- Map of partnerships in next-generation storage
- Technologies, products and services
- The risks this company carries
- Glossary, references and claim-to-source audit
1. ESS Tech in 30 seconds, and where it stands in next-generation storage
Oregon, U.S.One facility of about 200,000 square feet houses headquarters, R&D and manufacturing lines
Storage systems & operators (secondary)Iron flow batteries (primary) and sodium-ion battery systems (secondary). One segment
ESS Tech has developed an iron flow battery with the target that capacity does not fade over 20,000 charge-discharge cycles, but its revenue is very small and substantial doubt about its ability to continue as a going concern has been disclosed Sourced. Both the 10-K (March 2026) and the 10-Q (August 2026) say that cash is insufficient for the next 12 months and that there is substantial doubt. The company states that it needs more equity or debt, and that if it cannot raise it, it may have to scale back or cease operations, or seek protection under Chapter 7 or 11 of the U.S. Bankruptcy Code. First-half 2026 revenue was US$0.2 million (US$3.0 million a year earlier) and the net loss was US$31.5 million. On the business side, in April 2026 it signed a letter of intent for 8.5 GWh of sodium-ion batteries with Alsym Energy, and in July it launched a sodium-ion system called "Bridge". The company says it will keep developing iron flow technology but streamline its Wilsonville operations and redirect capital toward sodium-ion Sourced. This profile keeps technology and product descriptions, financial disclosures and the listing situation separate, as the company's own materials present them.
2. The logo and how the name is written
A note on names: the legal entity is ESS Tech, Inc.; the website and logo use ESS, Inc. (the logo reads "ESS INC ENERGY SOLUTIONS"). The iron flow product is called Energy Base in the 10-K and 10-Q (earlier generations: Energy Warehouse and Energy Center) and Horizon on the website from July 2026. The 10-Q still says Energy Base, and whether the two are the same product (a rename) could not be confirmed. The sodium-ion system is Bridge and the plant software is COMMAND (all company names). The logo image was taken from the one served by the company's official website (essinc.com).
Official site: https://essinc.com/3. Where the company sits in the field
ESS Tech falls mainly under "long-duration & new chemistries", with "storage systems & operators" as a secondary type added in 2026. The 10-K described the company as one specializing in iron flow batteries for long-duration storage. The 10-Q for June 2026 says it "develops, manufactures and integrates non-lithium energy storage solutions" using sodium-ion and iron flow technologies, and that its sodium-ion systems use cells bought from third parties, while the company manufactures and assembles the battery modules, housings, energy management systems and other key components Sourced. In other words, it has two faces: a new-chemistry company that makes the battery itself (iron flow), and a systems integrator that uses other companies' cells (sodium-ion). The strengths one would expect in this type are the company's "no thermal runaway with an aqueous electrolyte" and "widely available materials", and the weakness one would expect is "limited scale and track record" Our calculation (the categories and axes of assessment are our own framing, not the company's self-assessment). Others in the long-duration type include Form Energy (iron-air), Eos Energy Enterprises (zinc-based) and Invinity Energy Systems (vanadium redox flow).
4. Scale
The fiscal year runs January to December. The figures below are from the annual report (10-K) for 2025 and the quarterly report (10-Q) for the first half of 2026 Sourced.
| Indicator (US$ million) | Year to Dec 2024 | Year to Dec 2025 | First half 2026 [prior-year half] |
|---|---|---|---|
| Revenue | 6.3 | 1.6 | 0.2 [3.0] |
| Cost of revenue | 51.7 | 29.3 | 14.7 [16.2] |
| Gross profit / (loss) | (45.4) | (27.7) | (14.5) [(13.2)] |
| R&D expenses | 11.8 | 8.3 | 4.8 [3.9] |
| Loss from operations | (89.8) | (57.4) | (28.9) [(29.7)] |
| Net loss | (86.2) | (63.4) | (31.5) [-] |
| Cash flow from operating activities | - | (50.3) | (22.4) [-] |
| Other indicators | Value | As of |
|---|---|---|
| Cash and short-term investments | Cash US$14.5 million plus short-term investments US$7.5 million = US$22.0 million / cash US$10.8 million / about US$5.6 million (preliminary) | 31 December 2025 / 30 June 2026 / 31 July 2026 |
| Balance sheet | Total assets US$32.5 million, total liabilities US$35.2 million, so stockholders' equity of -US$2.7 million (a deficit). Accumulated deficit US$877.3 million | 30 June 2026 |
| Main obligations | An unsecured promissory note to Yorkville (YA II PN) of up to US$40 million (3% interest, 8% original issue discount). Financing obligations from the sale-leaseback with UOP, an affiliate of Honeywell (sale price US$10.5 million): US$5.8 million current plus US$8.7 million non-current | 30 June 2026 |
| Shares outstanding | 32.9 million (22.4 million at the end of 2025). A 1-for-15 reverse split on 23 August 2024 | 30 June 2026 |
| Revenue breakdown | Of 2025 revenue of US$1.58 million, US$2.38 million was from related parties. The remainder (-US$0.80 million) reflects reductions from winding down legacy contracts (our calculation: 158.3 - 237.9). First half 2026: customer A 61%, customer B 34% | Year to Dec 2025 / first half 2026 |
| Orders and projects | A backlog figure could not be found in the 10-K or 10-Q (individual projects are in section 5) | - |
The figures above are statutory figures set side by side, not an assessment of financial condition. The 10-K and 10-Q state that, given recurring losses and insufficient cash to fund operations for the next 12 months, there is substantial doubt about the company's ability to continue as a going concern. The company says that, after cost cuts and cash conservation (including a furlough of a substantial number of employees from 30 May 2025), it needs additional debt or equity financing in the near term. Those plans assume, among other things, that vendors continue to cooperate on payment plans for outstanding invoices, and the company says that if those assumptions prove wrong it may use up its capital sooner than expected. An 8-K says the offering of 20 August 2026 sold 6,400,000 shares at US$0.50 a share (expected net proceeds of about US$2.5 million). The company has disclosed several times that it fell short of the NYSE's listing standards (below), and on 2 October 2026 the NYSE suspended trading.
5. Resources committed to next-generation storage
ESS Tech is wholly a non-lithium storage business, so company-wide figures are almost entirely figures for next-generation storage. However, headcount and R&D spending are not split between iron flow and sodium-ion.
| Type of resource | What primary sources confirm | Status |
|---|---|---|
| People | 62 employees (31 December 2025, all full-time), of whom about 21 in R&D. R&D is in Oregon. A furlough of a substantial number of employees since 30 May 2025. More than 315 patents granted, applied for or in the pipeline | Sourced |
| Money (R&D and facilities) | R&D expense was US$8.3 million in 2025 (US$11.8 million in 2024) and US$4.8 million in the first half of 2026. The 10-K says about US$184.7 million has been invested since January 2019. In the first half of 2026 the company took abandonment charges of US$4.3 million after reassessing fixed assets in light of its current manufacturing activities. Wilsonville's capacity was about 560 MWh a year in 2025, and the 10-K described plans to reach 1.05 GWh a year with a second automated line and then 2.0 GWh (the position after the June 2026 streamlining could not be confirmed) | Sourced / partly not confirmed |
| Acquisitions, investments, joint ventures and divestments | (1) VoltStorage GmbH (Germany, iron-salt batteries): its intellectual property and assets were acquired in February 2026 for 100,000 shares and US$750,000. (2) UOP, an affiliate of Honeywell: in September 2023 a common stock and warrant purchase agreement (US$15 million prepayment), a supply agreement, a joint development agreement and a patent license agreement. In July 2025 a sale-leaseback of the stack assembly line (US$10.5 million; accounted for as a financing). (3) SB Energy (SoftBank group): a framework agreement of April 2021; the 10-K says no orders have been placed to date. (4) On 6 August 2026 a letter of intent for a business combination with a private company (non-binding; the counterparty is not disclosed) | Sourced |
| Universities, research institutes and public funding | DOE ARPA-E grant: some research was grant-funded, and the company granted the U.S. government a non-exclusive license (10-K). Export-Import Bank of the United States (EXIM): a loan facility of up to US$22.7 million (agreed 1 November 2024; no borrowings at 30 June 2026). U.S. Air Force Research Laboratory (AFRL): a US$9.9 million contract through Concurrent Technologies Corporation (29 January 2026). Joint research with a university could not be confirmed | Sourced / partly not confirmed |
| Investments in start-ups | Could not be confirmed | Not confirmed |
Next come the main projects and agreements. Stages are in the wording of the company's announcements, and plans and targets are Not yet confirmed.
| Project | Location | Size | Stage (in the announcements' wording) | Date | Source |
|---|---|---|---|---|---|
| Salt River Project (SRP), "Project New Horizon" | Florence, Arizona, U.S. | 5 MW / 50 MWh (iron flow, Energy Base) | A pilot. ESS sells capacity to SRP under a ten-year storage agreement. In March 2026 the company announced it was joining a collaboration of SRP and Google. Operating date could not be confirmed | 9 October 2025; 3 March 2026 | Reference 15, 16 |
| U.S. Air Force Research Laboratory (AFRL) / Concurrent Technologies | Alaska, U.S. (Clear Space Force Station) | Up to 27 MWh (iron flow) | Contract signed (US$9.9 million); part of a demonstration initiative | 29 January 2026 | Reference 17 |
| Alsym Energy | U.S. | 8.5 GWh of sodium-ion cells and modules | A letter of intent (strategic partnership). Whether it is binding is not stated in the announcement | 29 April 2026 | Reference 10 |
| Juniper Energy | California, U.S. and others | 500 MWh or more (sodium-ion). The first project is 10 MW / 80 MWh | A letter of intent, setting a framework | 2026 (no date on the company website) | Reference 14 |
| SB Energy | U.S. | Size not stated | A framework agreement of April 2021; the 10-K says no orders have been placed | As of 31 December 2025 | Reference 1 |
| UOP (Honeywell) | U.S. | Purchases of up to US$300 million by 2030 (the basis for issuing warrants) | Supply, joint development and patent licence. UOP has no obligation to place orders (10-K) | 21 September 2023 | Reference 1 |
According to the 10-K, ESS's iron flow battery works by charging in which ferrous iron (Fe2+) is oxidized to ferric iron (Fe3+) on the positive side and ferrous iron is reduced to metallic iron (plated) on the negative side, and by the reverse on discharge. The two electrolytes are held in tanks outside the cell and pumped through. The electrolyte is mainly salt, iron and water; power is set by the size of the cells and duration by the size of the tanks Sourced. The materials challenge is hydroxide formation, which the company says stopped researchers in the 1970s: hydrogen produced by side reactions at the negative electrode changes the electrolyte pH, and hydroxides clog the electrodes. The company says its patented "Proton Pump" converts that hydrogen back into protons and returns them to the positive electrolyte, which stabilizes pH and prevents hydroxide formation. The company says this makes a design of 20,000 cycles without capacity fade possible, but the 10-K states that this is "based on lab-scale results". Among the parts, the 10-K lists a porous separator, electrodes, the Proton Pump, and the limited use of high-cost materials such as platinum in manufacturing. The use of platinum (whether as a catalyst) could not be confirmed. The 10-Q also states that "as of 30 June 2026 we had limited iron flow products fully deployed" and that the sodium-ion and Energy Base products are still under development. No round-trip efficiency figure appears in the 10-K or 10-Q. See also our explainers on redox flow batteries and on long-duration storage (iron-air and zinc-based).
6. What it has done so far
| When | What happened | Why it matters |
|---|---|---|
| 2011 | Craig Evans and Dr. Julia Song formed the predecessor, Legacy ESS, and began advancing iron flow batteries | Per the 10-K |
| 2021 | April: framework agreement with SB Energy. October: listed through a business combination with a SPAC (ACON S2 Acquisition Corp.), renamed ESS Tech, Inc. | How it became public |
| September 2023 | With UOP, an affiliate of Honeywell: a common stock and warrant purchase agreement (US$15 million prepayment), a supply agreement, a joint development agreement and a patent license agreement | Relationship with a strategic partner |
| 2024 | 23 August: a 1-for-15 reverse stock split. 1 November: a loan facility of up to US$22.7 million agreed with EXIM | A public loan facility for production lines |
| 24 March 2025 | Notice from the NYSE that market capitalization and stockholders' equity were below US$50 million, so the listing standard (Section 802.01B) was not met. A cure plan was submitted on 7 May and accepted on 19 August | The start of the listing problem |
| May-July 2025 | 30 May: furlough of a substantial number of employees. 9 July: equity purchase agreement with Yorkville (up to US$25 million; completed in October). 10 July: sale-leaseback with UOP (US$10.5 million) | Securing cash |
| October-November 2025 | 9 October: announced the 5 MW / 50 MWh project with SRP. 14 October: promissory note to Yorkville (up to US$40 million). 13 November: set up an at-the-market program of up to US$75 million | A pilot project and fundraising |
| January 2026 | 29 January: a US$9.9 million contract with AFRL / Concurrent Technologies. Same day: a registered direct offering (net proceeds of about US$14 million) | A defense project and an equity raise |
| February-March 2026 | 10 February: acquired VoltStorage's assets. 3 March: announced joining the SRP and Google collaboration. 5 March: filed the 10-K (substantial doubt about going concern) | Adding iron flow IP, and the going-concern disclosure |
| April-June 2026 | 29 April: letter of intent with Alsym Energy for 8.5 GWh of sodium-ion. 9 June: NYSE notice that the share price was below US$1 (30-trading-day average US$0.98; Section 802.01C). 23 June: announced it will accelerate sodium-ion development and streamline Wilsonville operations | Reviewing the focus of the business |
| July 2026 | 1 July: the NYSE announced delisting proceedings and a trading suspension for the public warrants (GWH.W), which trade over the counter. 8 July: launched the sodium-ion system "Bridge". 16 July: changed the sales agents for the at-the-market program | Product addition and tidying of financing |
| August 2026 | 6 August: a letter of intent for a business combination with a private company (non-binding; the company targets a final agreement by the end of September 2026 and closing within the year). 20 August: sold 6,400,000 shares at US$0.50 and, at the same time, issued warrants for two shares per share bought (exercise price US$0.50) (closed 21 August). Letter of intent with Juniper Energy for 500 MWh or more of sodium-ion | Securing cash, and exploring a restructuring |
| September-October 2026 | 2 September: "Awardable" status in the U.S. Department of Defense's procurement marketplace (the company writes "Department of War"). 24 September: the NYSE decided to begin delisting proceedings (the company intends to appeal). 2 October: the NYSE decided to begin delisting proceedings on market-capitalization grounds (30-trading-day average below US$15 million) and suspended trading | The listing position |
7. What comes next
These items are company plans and expectations, not results Not yet confirmed. The official materials also contain the following plans.
- Keep developing iron flow technology while streamlining Wilsonville operations and reducing expenses and cash burn (announcement of 23 June 2026)
- Announce sodium-ion "container, rack and hardware solutions" and software to optimize battery and system health in the near future (announcement of 23 June 2026; Bridge was launched on 8 July)
- The first Juniper Energy project (10 MW / 80 MWh) is expected to use Bridge and the energy management system
- The 10-K had described a plan to expand Wilsonville to 1.05 GWh a year and then 2.0 GWh. The plan after the June 2026 streamlining could not be confirmed
- Yorkville promissory note: Tranche 2 matures on 27 February 2027 (10-Q). The company intends to use about US$1.5 million of the August offering's proceeds to repay it
Published round-trip efficiency or energy-density figures and operating results for the iron flow battery; the relationship between Energy Base and Horizon (whether it is a rename); the counterparty and final agreement for the business combination; the date of the SRP pilot's start of operation; whether the Alsym letter of intent is binding and the supply volume and price of the sodium-ion cells; the date and legal force of the Juniper Energy letter of intent; backlog; the latest cash balance (after the preliminary figure for 31 July 2026); the outcome of any request for NYSE review. None of this appears in the 10-K, 10-Q, 8-Ks or website reviewed.
8. What the company is aiming for in next-generation storage
We separate what the company says directly from what we read into it. Inference marks an interpretation of ours drawn from primary information.
| What we read from it | Primary information behind it | Status |
|---|---|---|
| The aim is "to offer non-lithium storage, from short durations to several days, from one company" | The company description on its website says it combines sodium-ion and iron flow to address storage from minutes to multiple days. The April 2026 announcement calls the two chemistries "complementary" | Sourced (company statement) |
| The current focus appears to be commercializing sodium-ion, which is closer to revenue, rather than expanding iron flow manufacturing | The 23 June 2026 announcement says it will streamline Wilsonville and redirect capital to sodium-ion. The 10-Q says near-term revenue is expected mainly from Bridge and Energy Base sales. An abandonment charge of US$4.3 million after the review of manufacturing | Sourced / Inference (priority) |
| Sodium-ion is a model of using other companies' cells and specializing in system design and assembly | The 10-Q says sodium-ion cells are bought from third parties and the company manufactures and assembles modules, housings and energy management systems. The Alsym letter of intent is also for adding cells and modules | Sourced |
| It is targeting AI data centers and defense | AI data centers head the list of uses for sodium-ion on the website. The January 2026 AFRL contract and the September procurement-marketplace status | Sourced / Inference (a trend) |
The reading that "commercializing sodium-ion, which is closer to revenue, is the focus rather than expanding iron flow manufacturing" rests on how the allocation of resources changed in 2026. The 10-K (March 2026) described, as a plan, a second automated line at Wilsonville and an expansion to 1.05 GWh a year and then 2.0 GWh Sourced. The 23 June announcement says that, while it will continue iron flow development, it will "streamline" Wilsonville operations, "reduce expenses and cash burn", and redirect capital to sodium-ion, which has "greater near-term revenue potential" Sourced. The 10-Q also records US$4.3 million of abandonment charges for fixed assets in the first half of 2026, explaining that it reassessed the use of assets "to respond to market and customer focus on the Bridge sodium-ion BESS and Energy Base product offerings" Sourced. We therefore read this as large-scale iron flow manufacturing expansion having a lower priority, at least for now Not yet confirmed. This is our interpretation, not a policy the company has stated. The company also says it will continue long-term iron flow development.
9. Map of partnerships in next-generation storage
What stands out in ESS Tech's partnerships is that its strategic partners (UOP, an affiliate of Honeywell, and SB Energy) are also related parties, under frameworks with no obligation to order Sourced. The 10-K says SB Energy is "under no obligation to place any firm orders at any price point" and has placed no orders to date, and that UOP likewise has no obligation to place additional orders. Of 2025 revenue, US$2.38 million was from related parties. The recent relationships (Alsym and Juniper Energy) are both at the letter-of-intent stage. Also, the supply terms for the sodium-ion cells and the counterparty to the 6 August 2026 business combination do not appear in the materials reviewed, and we do not speculate on them.
10. Technologies, products and services
Products are described within the 10-K, 10-Q and the company's website. Performance values are the manufacturer's stated values; where no test conditions are given we say conditions are unknown, and we make no comparison with other companies.
| Area | What the 10-K and website say | Note |
|---|---|---|
| Energy Base / Horizon (iron flow battery) | The electrolyte is mainly salt, iron and water; power is set by the stack size and duration by the tank size, independently. The 10-K describes a "gigawatt-hour scale, fully configurable product" and an "expectation of 20,000 cycles" (based on lab-scale results). The website's Horizon page says 16 to 48+ hours, the home page says "20 hours or more", and the April 2026 announcement says "8-24 hours", so the duration differs between documents. Design life of 20 years (website) | Round-trip efficiency and energy-density figures could not be confirmed. "No capacity fade over 20,000 cycles" is a lab-scale result, and operating results from full-scale units could not be confirmed |
| Bridge (sodium-ion battery system) | A 1.2 MWh basic unit (a 10-foot container). Stacked, it gives up to 4.8 MWh in the footprint of a standard 20-foot container. Discharge from 1 to 16+ hours depending on configuration. Operating temperature -40 °C to 50 °C, design life 20 years, simple forced-air cooling (website; announcement of 8 July 2026). Cells are bought from third parties (10-Q) | Launched in July 2026; the 10-Q describes it as under development. The cell supplier and volumes could not be confirmed |
| COMMAND and the energy management system | Plant-wide energy management, monitoring and optimization software | Website description only |
| Earlier generations (Energy Warehouse, Energy Center) | Initial products. No longer offered for sale; warranty and maintenance continue for units in the field (10-K). Revenue was reduced by winding down contracts | 2025 revenue was mainly from related parties |
| Manufacturing | A facility of about 200,000 square feet in Wilsonville with automated and semi-automated lines. Capacity of about 560 MWh a year in 2025. Streamlining announced in June 2026 | Current utilization could not be confirmed |
| Standards and certification | The 10-K and 10-Q give no status for standards such as UL 9540A or UL 1973 (none found) | No certificate or test report could be confirmed |
The company cites iron, salt and water, abundant and inexpensive materials, as a strength Sourced. However, an iron flow battery needs tanks, pumps, piping and electrolyte-management equipment in addition to the stack. The company says the balance-of-system parts are commercially available products and that its intellectual property and differentiation lie in the Proton Pump, power module, battery management system and electrolyte. The 10-K lists, as risks, past quality problems and delays in manufacturing and the fact that some products are still under development. The sodium-ion battery uses sodium instead of lithium, and the company says it removes thermal-runaway risk and reduces dependence on constrained critical minerals, but because the cells are bought from third parties (including under the Alsym letter of intent), cell performance (energy density, life, cost) depends on the supplier's technology Inference. See also our explainers on sodium-ion batteries, hard carbon anodes and redox flow batteries.
11. The risks this company carries
| Risk | Detail | Status |
|---|---|---|
| Continuing as a going concern | Both the 10-K and 10-Q state that there is substantial doubt about the company's ability to continue as a going concern. The company states that without more funding it could scale back or cease operations, liquidate assets or seek protection under Chapter 7 or 11. Liabilities exceed assets (stockholders' equity of -US$2.7 million), and cash was about US$5.6 million at the end of July 2026 (preliminary) | Sourced |
| Suspension and delisting of the shares | On 2 October 2026 the NYSE suspended trading, on a decision based on market capitalization (30-trading-day average below US$15 million), on top of a separate decision on 24 September 2026 (failure to regain compliance with the listing standard). The company expects over-the-counter trading and the 8-K says liquidity may fall. The deadline for requesting review is ten business days from notice | Sourced |
| Dilution | Shares outstanding rose from 22.4 million at the end of 2025 to 32.9 million at the end of June 2026. The August 2026 offering was at US$0.50 a share, with warrants for two shares per share bought (12,800,000 shares, exercisable after stockholder approval). An at-the-market program, a promissory note and warrants also exist | Sourced |
| Product maturity | The 10-Q says "as of 30 June 2026 we had limited iron flow products fully deployed" and that the sodium-ion and Energy Base products are under development. The 10-K cites the difficulty of scaling manufacturing and past quality problems and delays | Sourced |
| Revenue and customer concentration | Revenue was US$1.58 million in 2025 and US$0.2 million in the first half of 2026. Two customers were 95% of first-half revenue. No backlog figure is disclosed. The main strategic partners (SB Energy and UOP, an affiliate of Honeywell) have no obligation to order | Sourced |
| Related-party dealings | The 10-K describes the relationships with UOP, an affiliate of Honeywell (common stock and warrants, supply, joint development, patent license and sale-leaseback), and with SB Energy as risks involving possible conflicts of interest | Sourced |
| Change of strategy and restructuring | In 2026 the company widened its focus from iron flow to sodium-ion and signed a letter of intent for a business combination, so the direction of the business has changed in a short time. The letters of intent are either non-binding or not stated to be binding | Sourced / Not yet confirmed |
| Dependence on policy | The 10-K and 10-Q say that tax credits under the IRA and OBBB (Section 45X and the ITC) and sourcing restrictions tied to foreign entities of concern (FEOC) affect the business, and the company cites FEOC compliance in marketing sodium-ion as well (we have not checked the current state of the law against the legal text) | Sourced / Not yet confirmed |
| Competing approaches | The 10-K names lithium-ion, lithium iron phosphate, sodium-ion (including by CATL), vanadium and zinc-bromine batteries, sodium-sulfur batteries, compressed air, hydrogen and pumped hydro among its competitors. This profile does not rank them | Sourced |
| Difficulty of outside verification | Figures such as 20,000 cycles and a 20-year life are the manufacturer's stated values and lab-scale results, and neither test conditions nor third-party verification appear in the official materials | Not yet confirmed |
This profile summarizes a company and is not advice on the design, installation or safety of batteries or storage facilities. Installing and operating storage equipment is subject to national and local laws, standards and operators' safety rules.
12. Glossary
- Iron flow battery
- A battery in which iron-ion electrolytes are held in outside tanks and pumped through the cell for charge and discharge. Power (cell size) and capacity (tank size) can be set separately.
- Proton Pump
- ESS's patented technology. It converts hydrogen from side reactions at the negative electrode back into protons and returns them to the positive electrolyte, stabilizing pH and suppressing hydroxide formation (company description).
- Going concern
- The accounting assumption that a company will continue in business. Where there is substantial doubt, the company discloses it in the notes and the annual report.
- NYSE listing standards (802.01B / C / D, 802.02)
- Sections of the NYSE Listed Company Manual: market capitalization and stockholders' equity (B), a US$1 share price (C), an abnormally low trading price (D), and suitability for listing (802.02).
- ATM / SEPA / RDO
- An at-the-market program sells new shares gradually at market prices; a SEPA is a standby equity purchase agreement; an RDO is a registered direct offering to selected investors.
- Sale-leaseback
- Selling equipment and leasing it back at the same time. At ESS it is accounted for as a financing.
- Letter of intent (LOI)
- A document setting out basic terms before a definitive agreement. Whether it is binding depends on its wording.
- FEOC
- Foreign entity of concern. A concept that restricts sourcing under U.S. tax credits.
- ARPA-E
- The U.S. Department of Energy's Advanced Research Projects Agency-Energy. Some of ESS's research was grant-funded by it (10-K).
- 10-K / 10-Q / 8-K
- The annual / quarterly / current reports that U.S. listed companies file with the SEC.
13. References
- ESS Tech Form 10-K for the fiscal year ended 31 December 2025 (filed with the U.S. SEC on 5 March 2026). Business overview, revenue and profit, going concern, liquidity, employees, patents, related parties, risk factors. https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm
- ESS Tech Form 10-Q for the quarterly period ended 30 June 2026 (11 August 2026). First-half results, balance sheet, going concern, VoltStorage, subsequent events. https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm
- ESS Tech Form 8-K of 5 October 2026. NYSE suspension of trading (2 October 2026) and the start of delisting proceedings. https://www.sec.gov/Archives/edgar/data/1819438/000181943826000088/wk-20261002.htm
- ESS Tech Form 8-K of 30 September 2026. NYSE determination to begin delisting proceedings (24 September 2026, Section 802.02). https://www.sec.gov/Archives/edgar/data/1819438/000181943826000086/wk-20260924.htm
- ESS Tech Form 8-K of 21 August 2026. Registered direct offering (6,400,000 shares at US$0.50) and concurrent private placement of warrants. https://www.sec.gov/Archives/edgar/data/1819438/000181943826000077/wk-20260820.htm
- ESS Tech Form 8-K of 6 August 2026. Cash and short-term investments at 31 July 2026 (about US$5.6 million, unaudited). https://www.sec.gov/Archives/edgar/data/1819438/000181943826000067/wk-20260806.htm
- ESS Tech Form 8-K of 15 June 2026. NYSE notice on the share-price standard (Section 802.01C; notice of 9 June 2026). https://www.sec.gov/Archives/edgar/data/1819438/000181943826000044/wk-20260609.htm
- ESS Tech Form 8-K of 1 July 2026. Delisting proceedings and suspension of trading for the public warrants (GWH.W) (Section 802.01D). https://www.sec.gov/Archives/edgar/data/1819438/000181943826000056/wk-20260630.htm
- ESS Tech Form 8-K of 17 July 2026. Amendment of the at-the-market sales agreement (16 July 2026). https://www.sec.gov/Archives/edgar/data/1819438/000181943826000065/wk-20260716.htm
- ESS Tech Press release 'ESS Partners with Alsym Energy to Deliver 8.5 GWh of Non-Lithium Battery Energy Storage Solutions' (29 April 2026). https://essinc.com/ess-partners-with-alsym-energy/
- ESS Tech Press release 'ESS to Accelerate Sodium-Ion Battery Energy Storage System Development Following Surging Customer Interest' (23 June 2026). Streamlining of Wilsonville. https://essinc.com/ess-accelerates-sodium-ion-development/
- ESS Tech Press release 'ESS Introduces Bridge' (8 July 2026). Specifications of the sodium-ion system. https://essinc.com/ess-inc-introduces-bridge/
- ESS Tech Press release 'ESS Signs Letter of Intent for Proposed Business Combination' (6 August 2026). A non-binding letter of intent. https://essinc.com/ess-signs-letter-of-intent-for-proposed-business-combination/
- ESS Tech Company website news item 'ESS Signs 500 MWh Deployment Agreement' (the letter of intent with Juniper Energy). https://essinc.com/ess-and-juniper-energy-sign-agreement-for-500-mwh-of-sodium-ion-energy-storage-deployments/
- ESS Tech Press release 'SRP and ESS Announce New 50 MWh Long Duration Energy Storage Pilot Project' (9 October 2025). https://essinc.com/ess-and-srp-announce-50-mwh-storage-project/
- ESS Tech Press release 'ESS Announces Agreement to Join Salt River Project and Google Long Duration Energy Storage Collaboration' (3 March 2026). https://essinc.com/ess-joins-srp-and-google-energy-storage-collaboration/
- ESS Tech Press release 'ESS Tech Awarded $9.9 Million Contract from Concurrent Technologies Corporation and U.S. Air Force Research Laboratory' (29 January 2026). https://essinc.com/ess-awarded-9-9m-energy-storage-contract/
- ESS Tech Press release 'ESS Acquires VoltStorage GmbH Intellectual Property and Assets' (18 February 2026). https://essinc.com/ess-expands-long-duration-energy-storage-portfolio/
- ESS Tech Press release 'ESS Achieves “Awardable” Status Through Department of War’s Tradewinds Solutions Marketplace' (2 September 2026). https://essinc.com/ess-achieves-awardable-status-through-department-of-wars-tradewinds-solutions-marketplace/
- ESS Tech Company website, 'Horizon' (iron flow battery system). https://essinc.com/solutions/horizon/
- ESS Tech Company website, 'Bridge' (sodium-ion battery system). https://essinc.com/solutions/bridge/
- ESS Tech Company website home page (source of the logo image; product lines; company description). https://essinc.com/
14. Claim-to-source audit
| Claim in the text | Status | Source |
|---|---|---|
| Legal name, Delaware corporation, founding in 2011, the 2021 SPAC combination, headquarters (Wilsonville, about 200,000 square feet), 62 employees, about 21 in R&D, more than 315 patents | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm |
| Revenue, cost of revenue, gross loss, R&D, operating loss, net loss, operating cash flow, cash and short-term investments, and related-party revenue for 2024 and 2025 | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm |
| Revenue, cost of revenue, gross loss, R&D, operating loss, net loss, operating cash flow, cash, balance sheet, customer shares and shares outstanding for April-June and the first half of 2026 | Sourced | Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| Third-party revenue of -US$0.80 million in 2025 (158.3 - 237.9) | Our calculation | Our calculation (the difference between 10-K revenue and related-party revenue). |
| Substantial doubt about going concern (10-K and 10-Q), cost cuts and furlough, the stated need for more funding, the possibility of bankruptcy proceedings | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| Cash and short-term investments of about US$5.6 million at 31 July 2026 (company's preliminary figure, unaudited) | Sourced | Reference 6 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000067/wk-20260806.htm |
| The 20 August 2026 registered direct offering (6,400,000 shares, US$0.50, net proceeds of about US$2.5 million, warrants for 12,800,000 shares, a stockholder meeting within 60 days) | Sourced | Reference 5 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000077/wk-20260820.htm |
| The at-the-market program (November 2025, US$75 million) and its amendment (July 2026), Yorkville's equity purchase agreement and promissory note | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 9 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000065/wk-20260716.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| EXIM loan facility (up to US$22.7 million, 1 November 2024, no borrowings at 30 June 2026) | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| Agreements with UOP (Honeywell): supply, joint development, patent license, US$15 million prepayment; the US$10.5 million sale-leaseback; SB Energy's framework agreement with no orders | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| ARPA-E grant and the non-exclusive license granted to the U.S. government | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm |
| Acquisition of VoltStorage's assets (10 February 2026; 100,000 shares and US$750,000) | Sourced | Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm Reference 18 https://essinc.com/ess-expands-long-duration-energy-storage-portfolio/ |
| NYSE notices and decisions: 24 March 2025 (802.01B), 9 June 2026 (802.01C), 1 July 2026 (public warrants), 24 September 2026 (802.02), 2 October 2026 (market capitalization; suspension) | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 7 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000044/wk-20260609.htm Reference 8 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000056/wk-20260630.htm Reference 4 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000086/wk-20260924.htm Reference 3 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000088/wk-20261002.htm |
| The letter of intent with Alsym Energy (29 April 2026; 8.5 GWh), the 'complementary' description, and the 8-24 hour wording | Sourced | Reference 10 https://essinc.com/ess-partners-with-alsym-energy/ |
| Acceleration of sodium-ion development, streamlining of Wilsonville and the redirection of capital (23 June 2026) | Sourced | Reference 11 https://essinc.com/ess-accelerates-sodium-ion-development/ |
| Bridge: a 1.2 MWh basic unit, up to 4.8 MWh, -40 to 50 °C, 20-year design life, 1 to 16 hours, a 10-foot container (8 July 2026) | Sourced | Reference 12 https://essinc.com/ess-inc-introduces-bridge/ Reference 21 https://essinc.com/solutions/bridge/ |
| Horizon: 16 to 48+ hours, 20-year design life, non-flammable aqueous electrolyte; the home-page wording of '20 hours or more' | Sourced | Reference 20 https://essinc.com/solutions/horizon/ Reference 22 https://essinc.com/ |
| The business combination letter of intent (6 August 2026; non-binding; final agreement targeted by end-September and closing within the year) | Sourced | Reference 13 https://essinc.com/ess-signs-letter-of-intent-for-proposed-business-combination/ |
| The letter of intent with Juniper Energy (500 MWh or more; 10 MW / 80 MWh) | Sourced | Reference 14 https://essinc.com/ess-and-juniper-energy-sign-agreement-for-500-mwh-of-sodium-ion-energy-storage-deployments/ |
| SRP 'Project New Horizon' (5 MW / 50 MWh; a ten-year storage agreement) and the SRP and Google collaboration (March 2026) | Sourced | Reference 15 https://essinc.com/ess-and-srp-announce-50-mwh-storage-project/ Reference 16 https://essinc.com/ess-joins-srp-and-google-energy-storage-collaboration/ |
| The AFRL / Concurrent Technologies contract (US$9.9 million; up to 27 MWh; Alaska) | Sourced | Reference 17 https://essinc.com/ess-awarded-9-9m-energy-storage-contract/ |
| 'Awardable' status in the Department of Defense procurement marketplace (2 September 2026) | Sourced | Reference 19 https://essinc.com/ess-achieves-awardable-status-through-department-of-wars-tradewinds-solutions-marketplace/ |
| The principle of the iron flow battery (Fe2+/Fe3+, iron plating), the Proton Pump, the 20,000-cycle expectation (lab-scale), the limited use of platinum, the development stage of products, and the third-party source of sodium-ion cells | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| Wilsonville capacity in the 10-K (about 560 MWh in 2025; 1.05 GWh; 2.0 GWh) and the US$4.3 million abandonment charge in the first half of 2026 | Sourced | Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| The website's company description (combining sodium-ion and iron flow; minutes to multiple days) and the AI data center use for sodium-ion | Sourced | Reference 22 https://essinc.com/ Reference 21 https://essinc.com/solutions/bridge/ |
| The rise in shares outstanding (22.4 million to 32.9 million in 2026) | Sourced | Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm |
| The relationship between Energy Base and Horizon, the business combination counterparty and final agreement, the sodium-ion cell supply terms, round-trip efficiency and energy density, backlog, the date of the Juniper Energy letter of intent, and the outcome of any NYSE review request | Not yet confirmed | Nothing in the materials reviewed. We make no estimate. Could not be confirmed, and we do not assert that none exists (our note). |
| The four-type classification (Cells & materials; Long-duration & new chemistries; Storage systems & operators; Recycling) and the example companies | Our calculation | Our own classification. Company names are examples from those covered in this series. |
| The readings that large-scale iron flow manufacturing expansion has a lower priority, that sodium-ion cell performance depends on the supplier, and that the market focus is AI data centers and defense | Inference | Our own reading (not a policy stated by the company). Reference 11 https://essinc.com/ess-accelerates-sodium-ion-development/ Reference 2 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000074/ghw-20260630.htm Reference 1 https://www.sec.gov/Archives/edgar/data/1819438/000181943826000012/ghw-20251231.htm Reference 19 https://essinc.com/ess-achieves-awardable-status-through-department-of-wars-tradewinds-solutions-marketplace/ |
Last updated: 10 October 2026 / Troy Technical
The figures in this article come from statutory filings (Forms 10-K, 10-Q and 8-K) that ESS Tech, Inc. submitted to the U.S. Securities and Exchange Commission and from press releases on the company's website. Market-research estimates and press-report figures are not used. This is not an assessment of the company's financial condition or technology; the going-concern and listing information is given as disclosed. Passages marked "Inference" are our own reading of primary information and are not statements by the company.