All the fundraising deals in the LDES market (from Q1 2025 to Q1 2026)
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Between Q1 2025 and Q1 2026, startups in the LDES market raised a combined $527.6 million across 14 publicly disclosed funding rounds.
Most of that capital went to just two companies building air-based long-duration energy storage, while flow battery startups dominated the deal count with seven rounds.
Early-stage deals kept flowing throughout the period, signaling that investors are still backing new approaches to long-duration energy storage.
And if you want to better understand this new industry, you can download our pitch covering the LDES market.
Insights
- Air-based long-duration energy storage (compressed air and liquid air combined) captured 70% of all LDES market funding with just 2 out of 14 deals, showing how capital-intensive infrastructure-scale storage remains.
- Flow batteries accounted for half of all LDES market deals (7 out of 14), but no single flow battery company has emerged as the dominant winner yet.
- Q3 2025 was the most diversified quarter for LDES market funding: five deals, no round above $50 million, and the largest deal represented only 29.6% of the quarter's total.
- Goldman Sachs appeared in both of the two largest LDES market rounds (Hydrostor and Highview Power), backing compressed-air and liquid-air storage for a combined $371 million.
- The average LDES market deal size across all five quarters was $37.7 million, but that number drops to roughly $8.8 million if you remove the two largest air-based rounds.
- Strategic and infrastructure-focused investors (sovereign funds, industrial corporates, transition funds) were more prominent than traditional venture capital firms across LDES market deals.
- India and the Asia-Pacific region showed up repeatedly in LDES market funding, with VFlowTech, Sthyr Energy, Invinity Energy Systems, and Meine Electric all raising rounds with a regional focus there.
- Q1 2026 posted only $5.75 million across two deals in the LDES market, the quietest quarter in the dataset, as the period's large project financings had already closed.
- Highview Power's $171 million round alone made up 88.6% of Q4 2025 LDES market funding, a reminder that one large project financing can reshape quarterly totals.
In our LDES market deck, we will give you useful market maps and grids
Summary table of the funding deals in the LDES market (last 5 quarters)
We define the LDES market as electricity storage systems designed to discharge at rated power for at least 10 hours.
We include grid-connected and behind-the-meter assets whose primary function is shifting electricity over 10+ hours to multi-day timescales (across electrochemical, mechanical, thermal-to-power, and chemical storage technologies).
We exclude short-duration storage (<10h), demand response, and fuel/heat value chains that are not procured and operated as an electricity storage system.
You can also read our detailed analysis to understand how funding activity in the LDES market has evolved over the last few years.
Also, you should know that we have a dedicated page, updated weekly, with all the latest fundraising deals in the LDES market.
| Name | What they do | Amount ($M) | Quarter | Source(s) |
|---|---|---|---|---|
| Hydrostor | Builds compressed-air energy storage systems for power grids | $200.0M | Q1 2025 | Hydrostor |
| VFlowTech | Develops vanadium redox flow batteries for long-duration storage in Asia | $20.5M | Q2 2025 | VFlowTech |
| Sthyr Energy | Builds mechanically rechargeable zinc-air batteries for seasonal storage in India | $1.0M | Q2 2025 | Economic Times |
| ESS Tech | Makes iron-flow batteries for commercial and utility-scale storage | $31.0M | Q3 2025 | ESS Tech |
| Invinity Energy Systems | Sells utility-grade vanadium flow battery systems globally | $31.8M | Q3 2025 | Investegate |
| Fourth Power | Stores energy as heat in carbon blocks and converts it back to electricity | $20.0M | Q3 2025 | Business Wire |
| XL Batteries | Develops organic, non-flammable flow batteries for grid storage in the U.S. | $7.5M | Q3 2025 | XL Batteries |
| Unbound Potential | Builds membrane-free redox flow batteries for large-scale storage in Europe | $17.0M | Q3 2025 | Startup Ticker |
| Sizable Energy | Develops offshore pumped-hydro storage using ocean depth and gravity | $8.0M | Q4 2025 | Sizable Energy |
| Flux XII | Develops advanced aqueous flow battery materials for grid-scale storage | $3.95M | Q4 2025 | Business Wire |
| Highview Power | Develops liquid-air energy storage for utility-scale grid applications | $171.13M | Q4 2025 | Highview Power |
| Quino Energy | Develops water-based organic flow batteries for long-duration storage | $10.0M | Q4 2025 | pv magazine |
| Meine Electric | Develops iron-air batteries for long-duration storage in India | $0.75M | Q1 2026 | pv magazine India |
| Qnetic | Builds long-duration flywheel energy storage systems in the U.S. | $5.0M | Q1 2026 | Business Insider |
In our LDES market deck, we identify pain points entrepreneurs should prioritize
How has funding activity in the LDES market changed over time?
Q1 2025 was the most active quarter by total dollars raised in the LDES market, with $200 million, but that entire amount came from a single mega-round by Hydrostor.
Q1 2026 was the quietest quarter in the LDES market, with just $5.75 million across two deals, as the period's large project financings had already closed in prior quarters.
Total LDES market funding in Q1 2026 ($5.75M) dropped 97% compared to Q4 2025 ($193.1M), and it also dropped 97% compared to Q1 2025 ($200M, one year earlier).
If you strip out the two largest deals each quarter (Hydrostor in Q1 2025 and Highview Power in Q4 2025), the remaining LDES market funding looks much more even across quarters, with a steady flow of $5M-to-$30M rounds. That suggests the baseline deal activity in long-duration energy storage stayed consistent even when headline numbers swung wildly.
| Quarter | Number of deals | Total raised ($) | Comment |
|---|---|---|---|
| Q1 2025 | 1 | $200.0M | One massive compressed-air deal by Hydrostor drove the entire quarter. |
| Q2 2025 | 2 | $21.5M | A quieter quarter with two flow battery and metal-air deals in Asia. |
| Q3 2025 | 5 | $107.3M | The most diversified quarter with five mid-size LDES deals and no single dominant round. |
| Q4 2025 | 4 | $193.1M | Highview Power's $171M round for liquid-air storage made up nearly 89% of the total. |
| Q1 2026 | 2 | $5.75M | Two early-stage deals in iron-air and flywheel storage kept the pipeline alive. |
| All quarters | 14 | $527.6M | 14 LDES market deals over five quarters, heavily concentrated in two air-based rounds. |
In our LDES market deck, we identify repeatable patterns you can use if you’re building in this market
Which startups in the LDES market raised the largest rounds over the last months?
These startups raised the most recently in the LDES market:
- Hydrostor raised $200 million to accelerate deployment of its multi-gigawatt compressed-air energy storage pipeline across North America, Australia, and Europe.
- Highview Power raised $171.1 million to begin phase one of its 3.2 GWh liquid-air energy storage facility at Hunterston in Scotland.
- Invinity Energy Systems raised $31.8 million to expand vanadium flow battery manufacturing and grow its commercial presence in India and APAC.
- ESS Tech raised $31 million through an insider-led package to support its strategic reset and iron-flow battery commercialization.
- VFlowTech raised $20.5 million to scale vanadium flow battery manufacturing and add AI-driven energy management features.
- Fourth Power raised $20 million to commission its 1 MWh thermal-to-power storage demo and move toward commercial deployment.
- Unbound Potential raised $17 million to advance its membrane-free redox flow battery technology in early pilot projects across Europe.
- Quino Energy raised $10 million to scale organic flow battery manufacturing and commercialization in the United States.
- Sizable Energy raised $8 million to move from basin testing to sea trials for its offshore pumped-hydro storage system off Italy.
- XL Batteries raised $7.5 million to scale operations for its organic, non-flammable flow batteries and reduce reliance on foreign supply chains.
And, yes, we do cover most of them in our our beautiful pitch about the LDES market.
You may also want to check our ranking of the most funded startups in the LDES market as well as our list of the most valued startups.
In our LDES market deck, we answer all the common questions from investors and entrepreneurs
Is the LDES market shifting toward smaller or bigger deals?
Across all five quarters, the average LDES market deal size was $37.7 million, but that number is heavily pulled up by two very large air-based storage rounds from Hydrostor and Highview Power.
Quarter by quarter, the average LDES market deal size swung from $200 million in Q1 2025 (one deal) down to $10.75 million in Q2 2025, then $21.5 million in Q3 2025, $48.3 million in Q4 2025, and $2.9 million in Q1 2026. These swings are mostly driven by whether a given quarter included one of those large infrastructure-style financings.
If you exclude the two largest rounds (Hydrostor and Highview Power), the average deal size across the remaining 12 LDES market rounds drops to about $13 million, which gives a more realistic picture of where most long-duration energy storage startups are fundraising today.
| Quarter | Number of deals | Average deal size ($) | Deals below $2M | Deals above $50M |
|---|---|---|---|---|
| Q1 2025 | 1 | $200.0M | 0 | 1 |
| Q2 2025 | 2 | $10.75M | 1 | 0 |
| Q3 2025 | 5 | $21.46M | 0 | 0 |
| Q4 2025 | 4 | $48.27M | 0 | 1 |
| Q1 2026 | 2 | $2.88M | 1 | 0 |
| All quarters | 14 | $37.69M | 2 | 2 |
In our LDES market deck, we help you understand how the market is structured
How concentrated was funding activity in the LDES market?
LDES market funding was highly concentrated throughout the period: in four out of five quarters, the single largest deal accounted for more than 85% of total capital raised. The only exception was Q3 2025, where the top deal (Invinity Energy Systems at $31.8M) represented just 29.6% of the quarter's total.
When you look at the top 3 deals each quarter, concentration reaches 100% in most quarters because there were rarely more than four deals in any given period. This pattern suggests the LDES market is still at a stage where one or two large rounds can completely reshape the funding landscape.
| Quarter | Number of deals | % by Top 1 | % by Top 3 | % by Top 10 |
|---|---|---|---|---|
| Q1 2025 | 1 | 100.0% | 100.0% | 100.0% |
| Q2 2025 | 2 | 95.3% | 100.0% | 100.0% |
| Q3 2025 | 5 | 29.6% | 77.2% | 100.0% |
| Q4 2025 | 4 | 88.6% | 98.0% | 100.0% |
| Q1 2026 | 2 | 87.0% | 100.0% | 100.0% |
| All quarters | 14 | 37.9% | 76.3% | 100.0% |
In our LDES market deck, we have designed useful charts to give you full market clarity
Which categories in the LDES market received the most funding?
Air-based long-duration energy storage (compressed air and liquid air combined) raised $371.1 million across just 2 deals, capturing 70% of all LDES market funding. Hydrostor and Highview Power are both building large infrastructure-scale facilities, which explains why their rounds were so much bigger than everything else in the dataset.
Flow batteries came in second with $121.8 million across 7 deals, making flow battery startups the most active category by deal count in the LDES market. However, capital was spread across multiple chemistries (vanadium, iron, organic, aqueous), so no single flow battery company has pulled away from the pack yet.
Thermal-to-power storage ranked third with $20 million in a single deal from Fourth Power. Fourth Power's approach of storing energy as heat in carbon blocks and converting it back with thermophotovoltaics is still at demonstration stage, which explains the smaller funding total compared to more mature LDES categories.
| Category | Number of deals | Total raised ($) | Startups and amount |
|---|---|---|---|
| Air-based LDES (compressed air + liquid air) | 2 | $371.1M | Hydrostor ($200.0M); Highview Power ($171.1M) |
| Flow batteries | 7 | $121.8M | Invinity Energy Systems ($31.8M); ESS Tech ($31.0M); VFlowTech ($20.5M); Unbound Potential ($17.0M); Quino Energy ($10.0M); XL Batteries ($7.5M); Flux XII ($3.95M) |
| Thermal-to-power storage | 1 | $20.0M | Fourth Power ($20.0M) |
In our LDES market deck, we cover the latest tech updates shaping the market
Who are the biggest investors in the LDES market?
Goldman Sachs was the most prominent investor in the LDES market by total funded amount, appearing in 2 deals (Hydrostor and Highview Power) worth a combined $371.1 million. Goldman Sachs' involvement in both of the two largest rounds shows the firm's strong conviction in infrastructure-scale long-duration energy storage.
Atri Energy Transition also appeared in 2 LDES market deals (Invinity Energy Systems and Quino Energy) totaling $41.8 million. Atri Energy Transition backed both a vanadium flow battery company and an organic flow battery company, suggesting a deliberate strategy to diversify across flow battery chemistries.
Antares Ventures participated in 2 LDES market deals (VFlowTech and Sthyr Energy) worth a combined $21.5 million. Antares Ventures focused on Asia-based long-duration energy storage startups, backing both a vanadium flow battery and a zinc-air battery company.
Disclaimer: this investor list may be incomplete; we focus on publicly disclosed lead and prominent recurring investors, so some frequent minority participants may be underrepresented. "Total funded" does not represent the amount personally invested by an individual investor. Instead, it refers to the aggregate amount raised across all fundraising rounds in which the investor participated.
| Investor | Number of deals | Total funded ($) | Startups |
|---|---|---|---|
| Goldman Sachs | 2 | $371.1M | Hydrostor; Highview Power |
| Atri Energy Transition | 2 | $41.8M | Invinity Energy Systems; Quino Energy |
| Antares Ventures | 2 | $21.5M | VFlowTech; Sthyr Energy |
In our LDES market deck, we track adoption trends and shifts in consumer behavior
Related blog posts
- A complete list of funding deals in the LDES market
- The startups that have raised the most funding in the LDES market
