Startup landscape: Long-duration energy storage (LDES) — the companies to watch and why

The long-duration energy storage (LDES) market attracted over $6.4 billion in cumulative investment between 2020 and 2025, according to the Long Duration Energy Storage Council. Yet fewer than 3% of deployed grid storage projects worldwide exceed four hours of discharge duration. That gap between capital deployed and capacity installed defines the opportunity: the startups that solve cost, durability, and supply chain constraints for storage beyond lithium-ion's practical limits will capture a market that McKinsey estimates at $1.5 trillion in cumulative investment by 2040. This landscape maps the companies, technologies, and competitive dynamics shaping LDES across the Asia-Pacific region and globally.

Why It Matters

Grid operators face a structural problem. As variable renewable energy penetration exceeds 40% of total generation, short-duration lithium-ion batteries (typically two to four hours) cannot bridge multi-day supply gaps caused by weather patterns, seasonal variation, or extended low-wind periods. The International Energy Agency projects that grids with 60% or higher renewable penetration require between 80 and 140 GW of storage with eight-plus-hour duration by 2030 to maintain reliability.

The economics are shifting in favor of LDES. Lithium-ion costs have plateaued at approximately $140 per kWh for grid-scale systems as of early 2026, driven by lithium carbonate price volatility and manufacturing constraints. LDES technologies, which decouple power and energy components, offer the potential for energy capacity costs below $20 per kWh at scale, making them viable for durations where lithium-ion becomes prohibitively expensive.

Asia-Pacific markets are at the forefront. China's State Grid Corporation has mandated at least 30% of new storage capacity installations to include systems with eight-plus-hour duration by 2027. India's Solar Energy Corporation of India (SECI) issued 1 GW of LDES tenders in 2025. Australia's Capacity Investment Scheme has allocated AUD 1.8 billion specifically for LDES projects. These policy signals create near-term demand that startup companies are racing to fill.

For engineers evaluating technology choices, the landscape is complex. At least six distinct technology families compete for the same use cases, each with different maturity levels, cost profiles, and site requirements. Understanding which companies are advancing commercially, and which remain in demonstration, is essential for informed procurement and project planning.

Key Concepts

Discharge duration categories define the LDES market. Medium-duration systems (four to twelve hours) target daily arbitrage and peak shifting. Long-duration systems (twelve to one hundred hours) address multi-day weather events. Ultra-long-duration or seasonal storage (hundreds of hours) targets inter-seasonal energy shifting.

Technology families competing in LDES include mechanical (compressed air, gravity, liquid air), electrochemical (flow batteries, metal-air, sodium-ion), thermal (molten salt, heated rock, ice), chemical (hydrogen, ammonia), and hybrid approaches combining two or more mechanisms.

Levelized cost of storage (LCOS) measures the full-cycle cost per MWh discharged, including capital, operations, degradation, and end-of-life costs. LCOS below $100/MWh for eight-hour systems and below $50/MWh for hundred-hour systems are generally considered grid-competitive thresholds.

Round-trip efficiency (RTE) describes the percentage of energy recovered from storage relative to energy input. Lithium-ion achieves 85 to 92% RTE, while most LDES technologies range from 40 to 75%, creating a direct trade-off between duration capability and energy efficiency.

What's Working

Iron-air batteries are reaching commercial demonstration. Form Energy, the category leader, commissioned its first commercial-scale facility in Weirton, West Virginia in 2025, manufacturing iron-air battery systems designed for 100-hour discharge duration. The company secured over $800 million in total funding through early 2026, including a $450 million Series F led by TPG Rise Climate and GIC. Form Energy's technology uses iron oxidation (rusting) to store energy, with raw material costs below $6 per kWh for the active material. Great River Energy in Minnesota and Xcel Energy in Colorado have signed offtake agreements for multi-day storage systems to be deployed by 2027. The iron-air approach benefits from abundant, low-cost materials and avoids the critical mineral dependencies that constrain lithium-ion supply chains.

Vanadium and zinc-based flow batteries are scaling in China. Dalian Rongke Power, a subsidiary of the Chinese Academy of Sciences spin-out, operates the world's largest vanadium redox flow battery installation: a 200 MW / 800 MWh system in Dalian, Liaoning Province, commissioned in late 2024. The system provides eight hours of discharge duration for State Grid Corporation. VRB Energy and Invinity Energy Systems have deployed smaller installations (10 to 50 MWh) across Australia, Japan, and Southeast Asia. Zinc-based flow battery startup Eos Energy Enterprises has shifted from its earlier zinc hybrid cathode design to a Z3 platform optimized for manufacturing scale, securing a 300 MWh order from HoltConnect for deployment in Texas. Flow battery technology advantages include cycle life exceeding 20,000 cycles, independent scaling of power and energy capacity, and non-flammable electrolytes.

Compressed air energy storage (CAES) is expanding with adiabatic designs. Hydrostor, a Canadian company with significant Asia-Pacific project pipeline, uses Advanced Compressed Air Energy Storage (A-CAES) to achieve round-trip efficiencies above 60%, compared to roughly 42% for conventional diabatic CAES. Hydrostor has secured development agreements for projects totaling over 4 GW globally, including a 500 MW / 4 GWh facility in New South Wales, Australia, backed by AUD 480 million from the Australian Renewable Energy Agency (ARENA) and private investors. The company's approach uses purpose-built underground caverns rather than natural formations, enabling site flexibility. In China, CITIC CAES has commissioned a 100 MW adiabatic CAES demonstration plant in Zhangjiakou, Hebei Province, backed by CITIC Group and integrated into the region's wind energy infrastructure.

Gravity-based storage is moving from prototype to deployment. Energy Vault, a Swiss company listed on the NYSE, has pivoted from its original crane-based gravity concept to the EVx platform, which uses composite blocks within modular building structures. The company delivered a 25 MWh gravity storage system in Rudong, China, in partnership with China Tianying, and has a pipeline of over 1 GW of projects across the Asia-Pacific region. EV Storage, Energy Vault's subsidiary, reported a 75% RTE for its EVx system, competitive with pumped hydro for four to twelve hour durations. Gravitricity, a UK-based startup, completed a 250 kW prototype demonstration in Edinburgh and is developing a 4 MW commercial pilot using abandoned mine shafts in the Czech Republic.

What's Not Working

Cost targets remain aspirational for most technologies. Despite projections of LCOS below $50/MWh at scale, most first-of-a-kind LDES installations are delivering energy at $150 to $300/MWh, three to six times the target range. Manufacturing learning curves have been slower than lithium-ion's historical trajectory because LDES technologies lack the consumer electronics demand that initially drove lithium-ion scale.

Supply chain maturity is lagging investment momentum. Vanadium flow batteries face concentration risk: over 60% of global vanadium production comes from China and Russia. Iron-air technology avoids this specific risk but requires specialized manufacturing processes (electrode fabrication, electrolyte management) where supply chains are still being established. Several LDES startups report 18 to 24 month lead times for critical balance-of-plant components.

Permitting and interconnection timelines delay commercial validation. Hydrostor's Broken Hill project in Australia faced over two years of environmental review for its underground cavern construction. CAES projects generally face longer permitting processes than above-ground battery installations, adding project risk and cost. Grid interconnection queues across the US, Australia, and India now average three to five years for large storage projects.

Several high-profile technology pivots have shaken investor confidence. Eos Energy Enterprises restructured its balance sheet in 2025 after manufacturing yield issues with its Z3 zinc battery platform delayed commercial shipments. Malta Inc., a molten salt electro-thermal storage developer backed by Alphabet's X and Breakthrough Energy Ventures, reduced its workforce and narrowed its market focus after encountering higher-than-projected system costs during pilot operations. Highview Power, a liquid air energy storage company, delayed the commissioning of its 250 MWh CRYOBattery facility in the UK from 2024 to late 2026 due to construction and cost overruns.

Round-trip efficiency penalties remain significant for the longest durations. Hydrogen-based seasonal storage (electrolysis plus fuel cell) operates at 30 to 40% RTE, meaning 60 to 70% of input energy is lost. Thermal storage systems typically achieve 50 to 65% RTE. These efficiency losses are economically acceptable only when the alternative is curtailment of zero-marginal-cost renewables, limiting the addressable market for ultra-long-duration applications.

Key Players

Established Companies

• Form Energy: Iron-air battery developer with 100-hour discharge capability. Over $800 million raised. First commercial manufacturing facility operational in West Virginia. Offtake agreements with major US utilities.
• Hydrostor: Advanced compressed air energy storage with over 4 GW of project pipeline. AUD 480 million secured for Australian projects. Uses purpose-built underground caverns for site flexibility.
• Dalian Rongke Power: Operates the world's largest flow battery installation (200 MW / 800 MWh) in China. Subsidiary of Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
• Energy Vault: NYSE-listed gravity storage company with EVx platform. Delivered projects in China and has over 1 GW Asia-Pacific pipeline. Partnership with China Tianying.
• Invinity Energy Systems: UK-headquartered vanadium flow battery manufacturer. Projects deployed across Australia, UK, and North America. Merged VRB assets with redT in 2020.

Growth-Stage Startups

• ESS Inc.: Iron flow battery technology using all-iron chemistry with low-cost materials. Delivered systems to utilities including Sacramento Municipal Utility District. Targeting 4 to 12 hour duration applications.
• Ambri: Liquid metal battery developer using calcium and antimony electrodes. Backed by Bill Gates and Khosla Ventures. Completed first commercial installation in 2025 for a data center customer.
• Noon Energy: Carbon-oxygen battery technology targeting 100-hour duration at projected costs below $20/kWh energy capacity. Seed funding from Breakthrough Energy Ventures.
• e-Zinc: Zinc metal battery developer based in Toronto targeting industrial and utility-scale LDES. Backed by BDC Capital and Natural Resources Canada.
• Antora Energy: Solid-state thermal battery using carbon blocks heated to over 1,500 degrees Celsius. Targeting industrial heat and power applications. Backed by Lowercarbon Capital and Shell Ventures.

Key Investors and Funders

• Breakthrough Energy Ventures: Portfolio includes Form Energy, Malta Inc., Noon Energy, and Antora Energy. Over $2 billion fund focused on climate technologies with long development timelines.
• TPG Rise Climate: Lead investor in Form Energy's Series F. Over $7 billion in climate-focused assets under management.
• Australian Renewable Energy Agency (ARENA): Government agency providing grant funding for LDES demonstration projects. Allocated over AUD 500 million for storage technologies since 2020.
• India's Solar Energy Corporation (SECI): Government procurement agency issuing LDES tenders. 1 GW of LDES procurement initiated in 2025.

Action Checklist

1. Map duration requirements to technology families. For four to twelve hour applications, evaluate flow batteries and gravity storage. For twelve to one hundred hours, assess iron-air and advanced CAES. For seasonal storage, consider hydrogen pathways only where curtailment economics justify efficiency losses.
2. Assess supply chain risk by chemistry. Conduct a critical materials audit for any LDES technology under consideration. Vanadium, zinc, and antimony face different geographic concentration and price volatility profiles than iron-based systems.
3. Engage with utility procurement programs. Monitor LDES-specific tenders from SECI (India), ARENA (Australia), and state grid operators in China. Early engagement in procurement processes positions engineering teams to influence technical specifications.
4. Request reference data from operating installations. Before committing to a technology, require performance data from systems that have operated through at least two full seasonal cycles. Prioritize round-trip efficiency, degradation rates, and maintenance costs over nameplate specifications.
5. Plan for extended permitting timelines. For CAES and underground storage approaches, budget 24 to 36 months for environmental and geological permitting. For above-ground systems (flow batteries, gravity, thermal), standard industrial permitting typically applies.
6. Evaluate bankability and counterparty risk. Several LDES startups operate with negative cash flow and limited revenue history. Review balance sheet strength, offtake contract backing, and warranty structures before signing long-term procurement agreements.
7. Track policy signals for LDES mandates. China's eight-hour storage mandates, India's LDES tenders, and Australia's Capacity Investment Scheme are creating near-term market pull. Align technology evaluation timelines with regional procurement windows.

FAQ

What distinguishes LDES from conventional battery storage? LDES refers to energy storage systems designed to discharge for eight hours or more, and often for multiple days. Conventional lithium-ion batteries are typically optimized for two to four hour discharge. LDES technologies generally decouple power (MW) from energy (MWh) capacity, allowing energy capacity to be scaled independently at lower marginal cost. This makes them viable for applications like multi-day grid reliability and seasonal energy shifting where lithium-ion becomes cost-prohibitive.

Which LDES technology is most commercially mature? Pumped hydroelectric storage remains the most mature LDES technology globally, with over 160 GW installed. Among non-hydro technologies, vanadium redox flow batteries have the most deployed capacity, led by installations in China. Iron-air batteries (Form Energy) and advanced CAES (Hydrostor) are the most advanced among next-generation approaches, with commercial-scale projects in construction or early operation as of 2026.

What are the main risks of investing in LDES startups? Technology risk is significant: many LDES systems have fewer than three years of field operation data, making long-term degradation and maintenance costs uncertain. Manufacturing scale-up risk is another factor, as several companies have experienced yield and cost challenges when moving from prototype to production. Market risk exists where LDES-specific procurement mechanisms are not yet established, leaving projects dependent on general storage procurement processes that favor proven lithium-ion technology.

How does the Asia-Pacific LDES market compare to other regions? Asia-Pacific leads in both installed LDES capacity and near-term procurement pipeline. China has the world's largest flow battery installation and the most aggressive storage duration mandates. Australia has allocated significant public funding through ARENA and the Capacity Investment Scheme. India's SECI tenders represent the largest government-led LDES procurement outside China. By contrast, the US market relies more on state-level incentives and utility-led procurement, while Europe focuses on hydrogen-based seasonal storage linked to its broader hydrogen strategy.

What cost benchmarks should engineers use when evaluating LDES proposals? For eight-hour systems, target LCOS below $150/MWh for first-of-a-kind installations and below $80/MWh for nth-of-a-kind systems. For hundred-hour systems, current costs range from $200 to $400/MWh, with technology developers projecting below $50/MWh at manufacturing scale. Always compare proposals on a full LCOS basis, including installation, balance-of-plant, degradation over warranted lifetime, and decommissioning costs, rather than on energy capacity cost alone.

Sources

1. Long Duration Energy Storage Council. "Net-Zero Power: Long Duration Energy Storage for a Renewable Grid." LDES Council, 2025.
2. International Energy Agency. "Energy Storage Outlook 2025." IEA, 2025.
3. McKinsey & Company. "Net-Zero Power: Long Duration Energy Storage Investment Outlook." McKinsey, 2025.
4. Australian Renewable Energy Agency. "Capacity Investment Scheme: Long Duration Storage Program." ARENA, 2025.
5. BloombergNEF. "Long-Duration Energy Storage Market Outlook." BNEF, 2025.
6. Form Energy. "Iron-Air Battery Technology: Commercial Progress Report." Form Energy, 2025.
7. China National Energy Administration. "Energy Storage Development Plan 2025-2030." NEA, 2025.
8. Solar Energy Corporation of India. "LDES Procurement Tender Documentation." SECI, 2025.