Which startups have raised the most funding in the LDES market?
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In our LDES market deck, you will find everything you need to understand the market
The LDES market (long-duration energy storage) is attracting billions of dollars from venture capitalists, strategic investors, and public markets.
We built this ranking to track every LDES startup we could find, sorted by total equity raised, and we update it every month with the latest funding data.
Below you will find our latest dataset with 65 companies, funding details, key investors, and a confidence score for each entry.
And if you want to better understand this new industry, you can download our pitch covering the LDES market.
A quick summary table
| Metric | Value |
|---|---|
| Most funded LDES startup | Form Energy ($1.2B) |
| Second most funded LDES startup | Energy Vault ($745M) |
| Largest single LDES funding round | $405M (Form Energy, Series F) |
| Median LDES startup funding | $23M |
| Share of funding captured by the top 10 | ~72% |
| Median time since last round | ~21 months |
| LDES startups that raised funding in the last 12 months | 21 out of 65 |
| Total LDES startup equity tracked | ~$6.4B across 65 companies |
| Most active LDES venture investor | Breakthrough Energy Ventures (7+ portfolio companies) |
| Active private LDES startups in the dataset | 53 out of 65 (82%) |

In our LDES market deck, we show you long-term trends so you can make better decisions
Top startups in the LDES market ranked by total funding raised
Here is an updated table that ranks the top startups in the LDES market based on the total amount of funding they have raised to date.
The table also includes the total number of funding rounds, the date and size of the latest round, the financing type (e.g. Series A, equity financing), key investors, the startup's current status (active, IPO, acquired, or shut down), and a confidence score based on the data collected (we excluded startups with very low data confidence, to make sure everything is reliable).
If you're interested in knowing how much these startups are worth, you can check our list of the top startups in the LDES market ranked by valuation.
| # | Startup | What They Do | Total Raised ($) | Total Rounds | Last Round Date | Last Round Amount ($) | Last Round Type | Key Investors | Current Stage | Confidence |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Form Energy | Iron-air multi-day grid batteries | $1.2B | 7 | October 2024 | $405M | Series F | T. Rowe Price, GE Vernova, Capricorn | Active | Strong |
| 2 | Energy Vault | Gravity and hybrid grid storage | $745M | 4 | October 2025 | $300M | Preferred Equity | Orion Infrastructure Capital | IPO | Strong |
| 3 | Highview Power | Liquid-air long-duration storage | $663M | 4 | November 2025 | $166M | Growth Equity | Scottish National Investment Bank, Centrica, Goldman Sachs | Active | Strong |
| 4 | Hydrostor | Compressed-air long-duration storage | $485M | 4 | February 2025 | $200M | Growth Equity | Canada Growth Fund, Goldman Sachs Alternatives, CPP Investments | Active | Partial |
| 5 | EnerVenue | Metal-hydrogen grid batteries | $445M | 3 | October 2023 | $308M | Series B | Aramco Ventures, IDG Capital, SLB | Active | Full |
| 6 | ESS Tech | Iron flow long-duration batteries | $323M | 2 | January 2026 | $15M | Registered Direct Offering | Undisclosed institutional investors | IPO | Partial |
| 7 | Eos Energy Enterprises | Zinc-based long-duration batteries | $220M | 3 | June 2024 | $75M | Preferred Equity / Strategic Investment | Cerberus | IPO | Partial |
| 8 | Antora Energy | Thermal batteries for industry | $200M | 3 | February 2024 | $150M | Series B | Decarbonization Partners, Temasek, BlackRock | Active | Partial |
| 9 | Ambri | Liquid-metal grid batteries | $194M | 3 | August 2021 | $144M | Late-stage private round | Reliance New Energy Solar, Paulson & Co., Bill Gates | Acquired | Partial |
| 10 | Azelio | Thermal storage with Stirling engine | $180M | 5 | October 2022 | $27M | Rights Issue | Existing shareholders | Shutdown | Low |
| 11 | Sage Geosystems | Geothermal power and storage | $154M | 3 | January 2026 | $97M | Series B | Ormat Technologies, Carbon Direct Capital, SiteGround Capital | Active | Strong |
| 12 | Rongke Power | Vanadium flow batteries | $145M | 1 | April 2023 | $145M | Series B | Junlian/Legend Capital, Dalian Jintou, Rongtuo Capital | Active | Strong |
| 13 | Invinity Energy Systems | Vanadium flow battery systems | $132M | 3 | September 2025 | $33M | Subscription | Atri Energy Transition, Next Gen Mobility | IPO | Strong |
| 14 | VRB Energy | Vanadium flow batteries | $131M | 5 | September 2024 | $55M | Strategic equity / JV | Red Sun, Ivanhoe Electric | Active | Partial |
| 15 | Malta | Thermal long-duration energy storage | $108M | 3 | December 2023 | $22M | Series C Preferred | Siemens Energy Ventures, Alfa Laval, Breakthrough Energy Ventures | Active | Strong |
| 16 | CMBlu Energy | Organic flow battery storage | $107M | 1 | October 2023 | $107M | Strategic equity / Series D | STRABAG | Active | Partial |
| 17 | Brenmiller Energy | Thermal energy storage systems | $104M | 7 | September 2025 | $4M | Preferred Equity Closing | Alpha Capital Anstalt | IPO | Partial |
| 18 | Primus Power | Zinc-bromide flow batteries | $92M | 5 | March 2017 | $32M | Undisclosed | Success Dragon, Matador Capital, Anglo American Platinum | Active | Strong |
| 19 | Energy Dome | CO2-based long-duration storage | $71M | 3 | July 2023 | $16M | Series B extension | Barclays, Novum Capital Partners, Elemental Excelerator | Active | Strong |
| 20 | H2, Inc. | Vanadium flow battery systems | $67M | 4 | January 2025 | $16M | Bridge | STIC Investments, KRUN Ventures, Lighthouse Combined Investment | Active | Strong |
| 21 | e-Zinc | Zinc-air long-duration batteries | $58M | 3 | June 2024 | $31M | Series A2 | Evok Innovations, Mitsubishi Heavy Industries, Export Development Canada | Active | Strong |
| 22 | RedoxBlox | Thermochemical storage for heat/power | $41M | 3 | October 2024 | $30M | Series A extension | Prelude Ventures, Imperative Ventures, New System Ventures | Active | Strong |
| 23 | ESI Asia Pacific | Iron flow battery deployment | $40M | 1 | September 2024 | $40M | Strategic investment | Queensland Government | Active | Partial |
| 24 | Fourth Power | Thermal battery energy storage | $39M | 2 | September 2025 | $20M | Series A Plus | Munich Re Ventures, DCVC, Breakthrough Energy Ventures | Active | Full |
| 25 | Corre Energy | Compressed-air long-duration storage | $35M | 3 | February 2023 | $9M | Placing / Subscription | Institutional investors | Active | Full |
| 26 | VFlowTech | Vanadium flow battery systems | $34M | 4 | May 2025 | $21M | Series A2 | Granite Asia, EDBI, MOL PLUS | Active | Strong |
| 27 | Redflow | Zinc-bromine flow batteries | $34M | 3 | September 2023 | $8M | Post-IPO | Existing shareholders | Shutdown | Partial |
| 28 | Noon Energy | Carbon-oxygen ultra-long storage | $31M | 2 | January 2023 | $28M | Series A | Clean Energy Ventures, Aramco Ventures, Emerson Collective | Active | Full |
| 29 | VoltStorage | Iron-salt long-duration flow batteries | $31M | 2 | July 2022 | $24M | Series C | Cummins, Korys, EIT InnoEnergy | Acquired | Partial |
| 30 | Elestor | Hydrogen-bromine flow batteries | $30M | 2 | August 2022 | $30M | Series A | Equinor Ventures, Invest-NL, Royal Vopak | Active | Partial |
| 31 | Redox One | Iron-chromium flow batteries | $30M | 2 | February 2024 | $20M | Series A | Tharisa | Active | Strong |
| 32 | Quidnet Energy | Geomechanical underground energy storage | $29M | 4 | May 2024 | $10M | Series C | Hunt Energy Network | Active | Partial |
| 33 | Photoncycle | Seasonal hydrogen home energy storage | $23M | 2 | March 2026 | $17M | Series A | NordicNinja, Voima Ventures, Lifeline Ventures | Active | Full |
| 34 | XL Batteries | Organic flow batteries for grid | $18M | 2 | September 2025 | $8M | Seed | Merrin Investors | Active | Partial |
| 35 | Quino Energy | Organic aqueous flow batteries | $16M | 3 | November 2025 | $10M | Series A | Atri Energy Transition | Active | Full |
| 36 | Offgrid Energy Labs | Zinc-bromine stationary battery systems | $15M | 2 | September 2025 | $15M | Series A | Archean Chemicals Industries, Ankur Capital | Active | Partial |
| 37 | 1414 Degrees | Thermal storage for industrial heat | $15M | 5 | October 2025 | $1M | Placement | Existing shareholders | IPO | Strong |
| 38 | Time Energy Storage | Aqueous organic flow batteries | $15M | 1 | October 2023 | $15M | Series A | GL Ventures, Bondshine Capital, Su Venture Capital | Active | Strong |
| 39 | Allegro Energy | Water-based flow batteries | $12M | 2 | September 2024 | $12M | Series A | The Grantham Foundation, Lightbank, Origin Energy | Active | Partial |
| 40 | Ore Energy | Iron-air multi-day battery storage | $11M | 1 | May 2024 | $11M | Seed | Positron Ventures, SPRIND | Active | Full |
| 41 | Sinergy Flow | Sulfur-based long-duration flow batteries | $10M | 2 | March 2026 | $8M | Late Seed | CDP Venture Capital, 360 Capital, Exergon | Active | Full |
| 42 | MGA Thermal | Thermal blocks for heat storage | $10M | 4 | December 2024 | Undisclosed | Pre-Series B | Electrifi Ventures, Climate Salad | Active | Strong |
| 43 | Sizable Energy | Offshore pumped-hydro ocean storage | $8M | 2 | October 2025 | $8M | Seed | Playground Global, Exa Ventures, Verve Ventures | Active | Partial |
| 44 | Green Gravity | Mine-shaft gravity energy storage | $7M | 2 | October 2024 | $6M | Series A | HMC Capital, BlueScopeX, Pacific Channel | Active | Strong |
| 45 | Qnetic | Long-duration flywheel energy storage | $7M | 2 | March 2026 | $5M | Private round | SOSV, Kingscrowd Capital, D3VC | Active | Strong |
| 46 | Cheesecake Energy | Thermal plus compressed-air storage | $6M | 3 | August 2022 | $4M | Pre-Series A | BGF, Perivoli Innovations, Sir John Egan | Active | Strong |
| 47 | KEMIWATT | Organic flow batteries | $5M | 2 | October 2025 | $5M | Capital increase | Stolt Ventures, Impact Océan Capital, GO Capital | Active | Partial |
| 48 | StorEn Technologies | Residential vanadium flow batteries | $5M | 6 | June 2024 | $600K | Crowdfunding | Crowd investors, StartEngine, ANYSeed | Active | Partial |
| 49 | CellCube | Vanadium flow battery systems | $5M | 3 | August 2019 | $225K | Undisclosed | Invinity | Active | Low |
| 50 | Flux XII | Aqueous flow battery materials | $4M | 1 | November 2025 | $4M | Seed | The Grantham Foundation, WARF, gener8tor | Active | Full |
| 51 | STOLECT | Carnot battery electricity storage | $4M | 1 | May 2022 | $4M | Venture round | Undisclosed | Active | Full |
| 52 | Jolt Energy Storage Technologies | Organic flow battery materials | $4M | 2 | December 2024 | $4M | Series A | Undisclosed | Active | Strong |
| 53 | Gravitricity | Shaft-based gravity energy storage | $4M | 3 | June 2024 | $1M | Seed / Crowdcube | Crowdcube investors | Shutdown | Partial |
| 54 | HalioGEN Power | Membraneless redox flow batteries | $3M | 1 | January 2024 | $3M | Seed | SPRIND, University of Manchester | Active | Strong |
| 55 | Build to Zero | Industrial thermal storage | $3M | 1 | September 2023 | $3M | Seed | Axon Partners Group, Digital Five Investment | Active | Strong |
| 56 | Bryte Batteries | Nordic vanadium flow batteries | $2M | 2 | June 2023 | $1M | Seed extension | Kjeldsberg, Bjørn Simonsen, MP Pensjon | Active | Partial |
| 57 | Gravity Power | Deep-shaft pumped hydro storage | $2M | 1 | January 2009 | $2M | Series A | 21 Ventures, Quercus Trust | Active | Partial |
| 58 | VisBlue | Residential-commercial flow batteries | $2M | 3 | December 2017 | Undisclosed | Seed / follow-on | SOKI Holding, Borean Innovation | Active | Partial |
| 59 | Volterion | Flow-battery stacks | $1M | 3 | October 2017 | Undisclosed | Seed | HTGF, Fraunhofer Venture, EIT InnoEnergy | Acquired | Partial |
| 60 | Zhonghe Energy Storage | Flow battery materials and systems | $1M | 2 | August 2024 | Undisclosed | Angel | Hidden Hill Capital, CMB International, Sequoia China | Active | Partial |
| 61 | TerraStor | Advanced compressed-air grid storage | $1M | 1 | December 2023 | $1M | Seed | Plug and Play Tech Center | Active | Low |
| 62 | Rivus Batteries | Organic electrolytes for flow batteries | $609K | 1 | December 2023 | $609K | Seed | xista science ventures, NAVCAP, EIT InnoEnergy | Active | Strong |
| 63 | ARKLE Energy Solutions | Vanadium flow battery systems | $460K | 1 | March 2025 | $460K | Seed | pi Ventures, IPTIF | Active | Strong |
| 64 | Tharam-Thiran Green Energy Flow | Sulfur-iron flow batteries | $61K | 1 | June 2023 | $61K | Seed | Social Alpha, IIITDM Kancheepuram | Active | Strong |
| 65 | Carbo Energy | Waste-based long-duration flow batteries | $20K | 1 | March 2024 | $20K | Seed | Techstars | Active | Partial |

In our LDES market deck, we will give you useful market maps and grids
Key funding trends in the LDES market
Insights
- Form Energy alone accounts for roughly 25% of all identified equity funding across the 65 LDES startups tracked, which signals extreme capital concentration at the very top of the long-duration energy storage market.
- Breakthrough Energy Ventures appears as an investor in at least seven LDES companies (including Form Energy, Malta, Fourth Power, and RedoxBlox), making Breakthrough Energy Ventures the single most active venture fund in long-duration energy storage.
- The top five funded LDES startups collectively raised approximately $3.5B, while the bottom 30 combined raised under $150M, a steep power-law distribution that mirrors how capital flows in deep-tech energy sectors.
- Iron-air battery technology (led by Form Energy and Ore Energy) has attracted over $1.2B in combined LDES funding, more than any other single storage chemistry, reflecting strong investor conviction in iron-air cost trajectories.
- Sage Geosystems raised $97M in a single Series B in January 2026, the largest identified early-stage LDES round outside of Form Energy, signaling growing investor appetite for geothermal-based energy storage solutions.
- EnerVenue raised $308M in a single Series B round, the largest identified single venture round in the entire LDES dataset, driven by outsized conviction from Aramco Ventures and SLB in metal-hydrogen battery chemistry.
- Energy Dome, Sinergy Flow, and Quino Energy are all based in or connected to Southern European ecosystems, collectively raising over $97M and suggesting Italy is emerging as a notable LDES innovation cluster.
- Goldman Sachs entities appear across both Hydrostor and Highview Power, collectively backing over $1.1B in combined equity, which positions Goldman Sachs as the most capital-deployed traditional financial institution in the LDES market.

In our LDES market deck, we have collected signals proving this market is hot right now
A few word about our methodology
As you can see, we built a database that ranks LDES startups based on their total cumulative fundraising. To create this ranking, we reviewed many sources and cross-checked information across multiple places.
Whenever possible, we prioritized official company communications, since they are the most reliable source for funding amounts. When those were not available, we relied on reputable industry sources such as TechCrunch, Crunchbase, Financial Times or Forbes (to name a few).
We excluded random blogs, unverified websites, and any sources that could not be validated.
When funding rounds were announced in other currencies such as euros, Swiss francs, Singapore dollars, Australian dollars, or rupees, we converted them into approximate USD equivalents for consistency.
Sometimes different sources report slightly different numbers, or the exact round size is not fully disclosed. In those cases, we flag the uncertainty and assign a confidence label to each LDES startup, visible in the last column.
Here is what they mean.
Full confidence: The LDES company's equity fundraising history can be reconstructed completely from public sources. The rounds, dates, amounts, and key investors are clearly identified, with no meaningful gaps.
Strong confidence: The fundraising history is largely complete and reliable. There may be a small missing detail, such as incomplete investor information or a minor round with limited data, but the overall record is clear.
Partial confidence: The main fundraising rounds can be identified, but the record is incomplete or somewhat mixed. Some rounds may be missing or certain funding events may be difficult to separate clearly.
Low confidence: Public information is too limited, inconsistent, or ambiguous to reliably reconstruct the LDES company's equity fundraising history.
When the confidence level is too low, we take a conservative approach and exclude the company from the ranking. We don't want to include data that cannot be reliably verified.
This reflects how we conduct all our research, including the work behind our report covering the LDES market.
In a world where LLMs hallucinate and unreliable information is everywhere, our goal is simple: provide data you can trust.
If you want the full detail on a specific calculation, feel free to contact us and we will gladly explain.
Finally, know that we update the dataset once per month, so come back here if you need fresh information.

In our LDES market deck, we identify repeatable patterns you can use if you’re building in this market
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