Which company is leading on long-duration energy storage technology?

Rather than a single dominant player, the Long-Duration Energy Storage (LDES) market is led by a few pioneering companies specializing in distinct, non-lithium technologies designed to store electricity for 10 to 100+ hours.

The prominent leaders shaping the LDES landscape depend on the specific technology approach:

• Form Energy (Iron-Air Batteries): Widely considered a frontrunner in multi-day energy storage. Form Energy utilizes an ultra-low-cost iron-air battery system capable of delivering electricity for 100 hours. They have secured major high-profile utility projects and partnerships, such as with Xcel Energy and Google.
• Energy Dome (CO2-Based Thermodynamic Storage): Topping non-lithium intelligence leaderboards for commercial momentum, this Italian innovator uses a patented closed-loop thermodynamic process utilizing carbon dioxide(C O 2)open paren cap C cap O sub 2 close paren(𝐶𝑂2) to store and discharge electricity efficiently. They have gained massive traction through commercial agreements with major utilities and tech giants like Google.
• ESS Tech (Iron Flow Batteries): A prominent publicly traded manufacturer utilizing safe, sustainable iron flow technology for long-duration utility applications, avoiding reliance on scarce minerals like lithium or cobalt.
• Highview Power (Liquid Air Energy Storage): A leader in cryogenic energy storage, Highview uses liquid air(L A E S)open paren cap L cap A cap E cap S close paren(𝐿𝐴𝐸𝑆) to build massive, scalable gigawatt-hour systems suited for heavy industrial and utility grids.
• Sumitomo Electric & Invinity Energy Systems (Vanadium Redox Flow): Established veterans and specialists in vanadium flow batteries, which have decades of proven commercial operation for multi-hour grid balancing.

While short-duration grid storage is heavily dominated by lithium-ion giants like Tesla and Fluence, the true long-duration and multi-day storage frontier is being defined by these alternative technology developers.

Would you like to explore the cost economics, efficiency comparisons , or project timelines for a specific LDES technology like iron-air versus flow batteries?

There is no single clear winner in long-duration energy storage (LDES) yet. The leader depends on what you mean by “leading”: commercial deployments, breakthrough technology, cost potential, or ability to scale manufacturing. The field is still being shaped.

A current shortlist of the strongest contenders:

My read of the competitive landscape

• Best positioned today (commercial reality): Tesla — because it has manufacturing scale, bankable projects, and proven deployments.
• Most disruptive technology candidate: Form Energy — if iron-air batteries achieve their cost and durability targets, they could become a major solution for multi-day grid reliability.
• Best non-lithium grid-scale contenders: Hydrostor and Energy Dome.
• Most likely winners may be technology-specific rather than one company: lithium-ion may dominate 4–12 hour storage, while iron-air, flow batteries, thermal, compressed air, and CO₂ systems compete for 12–100+ hour applications.

If you mean “which company is most likely to become the next big energy-storage winner for investors?”, the ranking would look different than if you mean “who has the best technology?”.

My read of the competitive landscape

When it comes to Long-Duration Energy Storage (LDES) —typically defined as systems capable of discharging electricity for 8 to 100+ hours—there isn’t just one single runaway market leader. Instead, leadership is split among a few pioneering companies championing different non-lithium technologies designed specifically for multi-day storage.

The standout leaders and innovators driving the LDES sector include:

• Form Energy - Widely considered a frontrunner for multi-day storage, Form Energy has captured massive industry attention and funding for its breakthrough iron-air battery technology . Their systems are designed to deliver a staggering 100-hour discharge duration at an ultra-low cost, making continuous renewable power viable.
• Energy Vault - A prominent player utilizing gravity-based and kinetic energy storage, alongside a broader portfolio that includes green hydrogen and multi-day storage solutions. They have scaled internationally with massive commercial utility projects deploying their heavy-load mechanical systems.
• Invinity Energy Systems - Recognized as a leading global manufacturer of vanadium flow batteries . Invinity specializes in utility-grade, long-duration chemical storage that scales reliably past traditional limits, with extensive deployments across international power grids.
• Energy Dome - Gaining significant traction for its proprietary CO2-based energy storage technology , which achieves around 10 hours of duration using a closed-loop thermodynamic process that compresses and decompresses carbon dioxide.
• Hydrostor - A leader in Advanced Compressed Air Energy Storage (A-CAES) , replacing fossil-fuel peaker plants with utility-scale underground compressed air systems capable of 8-plus-hour durations.

(Note: While traditional short-to-medium-duration grid storage is heavily dominated by lithium-ion giants like Tesla and Fluence , true long-duration and multi-day category leadership belongs to the specialized innovators above).

Are you looking at LDES for a specific use case (like utility-scale grid backup or industrial power), or are you interested in a particular technology type (like mechanical gravity vs. chemical flow batteries)?

If you mean who is furthest ahead in genuinely long-duration storage (roughly 10–100+ hours), rather than conventional 2–4-hour lithium-ion batteries, my pick today is Form Energy.

My current ranking

1. Form Energy — strongest overall

• Its iron-air battery is designed for 100 hours of discharge, dramatically longer than conventional lithium-ion.
• It has moved beyond the lab: California has approved a Form system, and the company has major utility/data-center commitments.
• The key question is execution at commercial scale: iron-air is a much less proven manufacturing platform than Li-ion.

2. Hydrostor — strongest non-battery contender

• Its advanced compressed-air technology is aimed at 8–16+ hour storage.
• Hydrostor has a pipeline exceeding 7 GW, including the 500 MW/4 GWh Willow Rock project in California.
• This is particularly interesting for utilities because the systems can potentially operate for decades rather than being replaced like batteries.

3. Energy Vault — strongest diversified commercial platform

• It has deployed gravity, battery and hydrogen-based systems, with 1.4 GWh deployed since 2023 according to its project portfolio.
• Its 2026 backlog and operating/development portfolio have grown substantially, although much of that business now encompasses conventional battery storage and AI infrastructure as well as truly LDES.

4. Eos Energy Enterprises — interesting flow-battery play

• Zinc-based batteries avoid some of lithium-ion's constraints and are well suited to stationary applications.
• Wood Mackenzie identified Eos, Form and Hydrostor as the three LDES companies that had raised more than $1 billion since 2021.

The important distinction

There isn't really one LDES winner yet. The market is splitting by duration:

That's why Form Energy is my answer if "leading" means technological leadership in very long-duration storage, while Hydrostor may have the more compelling utility-scale infrastructure proposition for 8–24 hours.

One caveat: Wood Mackenzie reported that global LDES deployments exceeded 15 GWh in 2025, but 93% of cumulative installations were in China, and falling lithium-ion prices are pushing conventional batteries into longer-duration applications. Utility Dive So the eventual winner may be less about the most novel chemistry and more about $/MWh, bankability, manufacturing scale, and project finance.

If you're asking from an investment perspective, I'd rank these companies quite differently—I can give you a Form Energy vs. Hydrostor vs. Eos vs. Energy Vault investment-style comparison, including technology risk, commercialization stage, moat, and likely market size.

Here are top web results for exploring this topic:

GreyB·https://greyb.com 6 Long Duration Energy Storage Companies and Startups - GreyB 2. Highview Power. Highview Power is a major global provider of Long Duration Energy Storage (LDES). The company provides a liquid-air energy storage solution that can deliver enough electricity to po Utility Dive·https://www.utilitydive.com**Long**-**duration energy storage** deployments rose 49% in 2025 The report found overall funding for LDES fell 30% globally in 2025, excluding a nearly $1.8 billion commitment by the U.S. Department of Energy to Hydrostor, a Canadian company working to commerciali Net Zero Insights·https://netzeroinsights.com Who Are The LDES Market Leaders? - Net Zero Insights Who Are The LDES Market Leaders? September 20, 2024. Linkedin Envelope. Long-Duration-Energy Storage (LDES) has quickly become pivotal in driving the renewable energy transition forward. By 2040, it's energystoragesolution.net·https://energystoragesolution.net/long-duration-energy-storage-companies/**Top** 10 Long Duration Energy Storage Companies of 2026 The most important companies to compare today include Form Energy, ESS Tech, Invinity Energy Systems, Hydrostor, Highview Power, Energy Vault, Rondo Energy, Malta, Quidnet Energy, and e-Zinc. That lis Fluence | A Siemens and AES Company·https://fluenceenergy.com Fluence | A Siemens and AES Company Fluence is a global market leader in energy storage products and services, and cloud-based software for renewables and storage assets. Energy Tech Review·https://www.energytechreview.com ESS Tech , Inc. | Top Long Duration Energy Storage Technology 2025 These policy goals have created a unique opportunity for long-duration energy storage (LDES) technologies to deliver this value. ESS Tech, Inc. is emerging as a frontrunner in this space with its Amer ESS, Inc.·https://essinc.com ESS, Inc.: Home Iron Flow Battery Technology. Iron flow batteries are designed for long-duration energy storage, delivering reliable power for 20 hours or more with minimal degradation over decades of operation. Usin Econ Market Research·https://www.econmarketresearch.com**Top Long**-Duration Energy Storage Companies in 2026 Form Energy's 100-hour platform, Hydrostor's 4,000 MWh Willow Rock project, Energy Dome's 200 MWh systems and Highview Power's 300 MWh liquid-air project demonstrate how different engineering approach MarketsandMarkets·https://www.marketsandmarkets.com**Top Companies** in Long Duration Energy Storage Industry Top Companies in Long Duration Energy Storage Industry. Sumitomo Electric Industries, Ltd. (Japan),; ESS Tech, Inc. (US),; Energy Vault, Inc. (US), · Top Companies in Long Duration Energy Storage Indu Reddit·https://www.reddit.com What are the companies /technologies for long term electricity storage?Round trip efficiency is also less important. The long term storage will only be used for maybe around 10% of the time, so, the cost of the losses are only 10% of the price of generation. Given these

If by long-duration energy storage (LDES) you mean storage capable of delivering electricity for 10–100+ hours, I’d put Form Energy at the top right now—especially for the U.S. grid.

My ranking

1. Form Energy — strongest overall LDES contender

• Its iron-air battery is designed for up to 100 hours of discharge, targeting the exact problem LDES is meant to solve: multi-day grid reliability.
• Form just raised $750 million, bringing total funding above $2 billion, and its commercial backlog reportedly reached 80 GWh.
• Its largest announced project is a 300 MW / 30 GWh system for Xcel Energy and Google in Minnesota.
• The key question is no longer just whether the chemistry works, but how rapidly Form can manufacture it at competitive cost.

2. Energy Vault — strongest diversified/technology-agnostic player

• It has gravity storage, batteries and green-hydrogen storage, and is pursuing both long- and multi-day applications.
• It has moved beyond being purely a technology bet and is building a broader storage-development/ownership platform.

3. ESS Inc. — strongest flow-battery specialist

• Its iron-flow technology is particularly attractive for 8–12+ hour applications because the electrolyte doesn't degrade in the same way conventional batteries do.
• It has active utility and government projects, including a planned system for the U.S. Space Force.

4. Hydrostor — major contender for very long duration

• Its underground compressed-air approach is potentially well suited to multi-day storage and very large installations.
• The downside is that projects are geographically and geologically constrained.

5. Highview Power — interesting multi-day contender

• Liquid-air energy storage can provide long-duration storage without relying on lithium.
• Highview raised $170 million for its 3.2-GWh project in Scotland.

The important distinction

If you mean "who is winning energy storage overall?", the answer is different. CATL is currently the global leader in lithium-ion grid-storage battery shipments, with about 27% of the global ESS battery market in H1 2026.

But lithium-ion is generally a 2–8 hour solution. LDES is a different technological and economic category.

So my short answer is:

Form Energy is currently the company I'd consider the leading pure-play LDES technology company, particularly for 24–100-hour storage. The really interesting investment question is whether Form's iron-air economics will beat flow batteries, compressed air, gravity and increasingly cheap lithium/sodium-ion systems once all are deployed at scale. That's where the competitive landscape gets much more interesting.

There is no single clear-cut "winner" leading the entire long-duration energy storage (LDES) market, as leadership is split between massive lithium-ion deployment giants and innovative non-lithium technology pioneers targeting multi-day storage.

Instead, market leadership depends on the specific metric—whether measured by current grid deployment volume or pioneering breakthrough tech for 8-to-100+ hour storage:

• The Scale Leader (Lithium-Ion): Tesla and traditional heavyweights like BYD and CATL dominate total gigawatt-hours deployed on the grid. While lithium-ion is traditionally built for 2-to-4 hour windows, scaled lithium-ion projects continue to win the largest volume of utility and government bids globally for shorter-end LDES requirements (up to 8 hours).
• The Multi-Day Technology Leader: Form Energy is widely recognized as a premier pioneer specifically for ultra-long duration storage. They utilize breakthrough iron-air battery technology designed for 100-hour discharge, backed by high-profile massive framework agreements with major utilities and tech giants like Google and Xcel Energy.
• The Non-Lithium Commercial Leader: Energy Dome (a carbon-dioxide battery innovator) consistently tops non-lithium LDES leaderboards for commercial execution and high-profile offtake agreements (including deals with Google), bringing 10-hour thermodynamic storage systems to market faster than many peers.
• Mechanical & Compressed Air Leaders: Hydrostor (advanced compressed air) and Energy Vault (gravity and kinetic storage) are leading the charge in mechanical and large-scale infrastructure solutions that bypass chemical batteries entirely for 8-hour-plus durations.

Would you like to focus on a specific chemistry (like iron-air vs. flow batteries) or look at utility projects in a certain region?

If by long-duration energy storage (LDES) you mean technologies designed to discharge for 8–100+ hours, rather than conventional 1–4 hour lithium-ion batteries, I’d put Form Energy in the lead right now—particularly for commercialization of a new, non-lithium LDES technology.

My current ranking

Why Form stands out: it has moved beyond the pilot stage toward mass production of its iron-air system. In August 2026, Form raised $750 million, taking total funding above $2 billion; its commercial project backlog reportedly reached 80 GWh, and its West Virginia factory is being scaled for production. Its technology is designed to store electricity for roughly 100 hours, using iron oxidation/reduction rather than lithium-ion chemistry.

There is an important caveat: “leader” depends heavily on what you mean by LDES. A recent industry ranking, for example, put Tesla and Chint Power at the top overall because long-duration lithium-ion currently has enormous deployment and low capex, while Hydrostor ranked highly among non-lithium technologies.

If I were evaluating the companies as investments

I'd separate them into three buckets:

• 🥇 Form Energy — best bet on 100-hour storage becoming a major new category
• 🥈 Hydrostor — arguably the strongest utility-scale alternative, with a 7-GW project pipeline and major engineering/industrial partnerships.
• 🥉 Energy Vault — strongest public-company exposure, although its business has broadened considerably beyond its original gravity-storage concept. It reported more than 1 GW under control, in construction, or operating and a backlog above $1.3 billion in Q1 2026.

So, if you force me to name one: Form Energy.

If you're asking because you're considering investing in LDES, I can also rank the top 10 companies by technological moat, commercialization probability, and potential investor upside—which produces a rather different ranking.

If I had to pick one company leading in long-duration energy storage (LDES) technology today, I’d pick Form Energy—particularly for multi-day grid storage.

Why Form Energy stands out

• 100-hour duration: Its iron-air battery is designed to discharge continuously for roughly four days, substantially beyond conventional lithium-ion systems.
• Commercial momentum: Form's contracted/project backlog reportedly reached 80 GWh, up from 20 GWh earlier in 2026.
• Major financing: In August 2026, Form raised another $750 million, taking cumulative funding above $2 billion. The financing is intended to scale its West Virginia manufacturing and commercial deployments.
• Real utility-scale deployments: Its largest announced project involves 300 MW / 30 GWh for Xcel Energy and Google's planned data center in Minnesota.
• Potentially compelling economics: Iron and air are abundant, inexpensive materials, giving the technology a fundamentally different cost structure from lithium-ion.

The important caveat is that LDES isn't one technology category, so the "leader" changes depending on what you're looking for:

Hydrostor is particularly interesting: it has a 7-GW project pipeline and is advancing its 500-MW Willow Rock project in California, while partnering with Hatch on engineering and execution.

One broader market ranking is worth noting: the 2026 Energy Storage Report says Tesla and Chint Power currently lead overall LDES vendor rankings because long-duration lithium-ion has much greater deployment, while among non-lithium technologies Form Energy, Hydrostor and ESS are among the notable contenders.

Bottom line: If your question is "Which company has the best shot at becoming the dominant provider of true multi-day grid storage?", Form Energy is my #1. If you're asking from an investment perspective, however, I'd evaluate Form, Hydrostor, Energy Vault, ESS, and Highview quite differently because technology leadership, commercial scale, and shareholder opportunity aren't the same thing.

Identifying a single company leading in long-duration energy storage (LDES) technology depends on whether you measure leadership by short-term deployment volume (where lithium-ion giants dominate) or by commercialization of true multi-day, non-lithium solutions.

The LDES market is categorized by several standout innovators and market leaders specializing in different technologies:

• Form Energy is a prominent pioneer in multi-day storage, focusing on iron-air battery technology designed to store electricity for 1 0 0+ hours at a low cost using abundant materials. They continue to pull in massive venture backing (such as a $750 million Series G round) and are actively scaling US manufacturing.
• ESS Tech, Inc. (ESS Inc.) is a leading manufacturer of iron flow long-duration energy storage systems (3-12+ hours) utilizing earth-abundant materials like iron, salt, and water to provide safe, non-toxic, and sustainable grid-scale capacity.
• Invinity Energy Systems is recognized as a leading global manufacturer of utility-grade vanadium redox flow batteries (VRFBs), frequently securing major international projects for non-lithium, multi-hour capacity.
• Energy Vault is a notable market player offering a broad portfolio spanning gravity-based energy storage and various short-to-long duration hybrid systems.
• Hydrostor is a frontrunner in advanced compressed air energy storage (CAES), securing substantial government and private financing for utility-scale, multi-hour underground storage projects.
• Tesla Energy and CATL lead the broader stationary storage market in pure deployment gigawatt-hours, though their dominant grid installations typically cluster in the shorter 2-to-8 hour duration window rather than multi-day LDES.

If you're evaluating these for a specific project or investment, would you prefer to focus on multi-day (100+ hours) tech like iron-air, or shorter multi-hour (8-24 hours) options like flow batteries and compressed air?