Best Long-Duration Energy Storage Companies in 2026
Long-duration energy storage (LDES) holds energy for many hours or even days, helping shift abundant renewable generation to when it is needed. These companies offer technologies built for extended discharge, beyond the typical 2-4 hour lithium-ion window.
Top Long-Duration Storage Companies
1. Energy Vault
A major storage company offering gravity and hydrogen storage in addition to batteries, technologies aimed squarely at long-duration applications, paired with advanced software and operations services.
Key Features: Gravity Storage, Hydrogen Storage, Enterprise Systems, Configurable
2. ESS, Inc.
Iron flow battery systems engineered for consistent output over prolonged durations, a core long-duration chemistry for enterprise and utility use.
Key Features: Design Build, Enterprise Systems, Commercial Systems
3. Fluence
A market-leading BESS provider whose configurable, enterprise-grade systems can be scaled to longer-duration lithium-ion deployments for utilities and large projects.
Key Features: Enterprise Systems, Configurable, Product Manufacturer
4. Wärtsilä
Turnkey grid-scale BESS and management software that can be sized for multi-hour duration as part of utility and renewable-firming projects.
Key Features: Enterprise Systems, Power Management Software
Long-Duration Storage Technologies
- Iron flow batteries - Use abundant iron-based electrolyte for long, repeatable discharge.
- Gravity storage - Raise and lower mass to store and release potential energy.
- Hydrogen storage - Convert electricity to hydrogen for long-term energy holding.
- Scaled lithium-ion - Larger capacity ratios extend lithium systems toward longer durations.
Frequently Asked Questions
What is long-duration energy storage?
Long-duration energy storage (LDES) generally refers to systems that can discharge for many hours, often 8 hours or more, and in some cases days. It complements shorter-duration lithium-ion by bridging longer gaps in renewable generation.
Which technologies are used for long-duration storage?
Common approaches include flow batteries (such as ESS, Inc.'s iron flow chemistry), gravity storage, and hydrogen storage, all of which Energy Vault and ESS, Inc. represent in this directory. Lithium-ion can also be configured for longer durations.
Why does long-duration storage matter?
As grids add more solar and wind, longer-duration storage helps shift surplus daytime energy into evenings and through low-generation periods, improving reliability and reducing curtailment.
See also our utility-scale companies guide or compare Energy Vault vs ESS, Inc.