Best Battery Energy Storage System (BESS) Companies in 2026
Looking for a battery energy storage system partner? These are the leading BESS companies serving commercial, industrial, and utility-scale projects, spanning hardware manufacturers, system integrators, software providers, and full-service developers.
Top BESS Companies
1. Fluence
A market leader in BESS with a comprehensive ecosystem of scalable products, services, and digital applications, ranging from utility-scale solutions to plug-and-play commercial offerings.
Key Features: Enterprise Systems, Commercial Systems, Configurable, Product Manufacturer
2. Wärtsilä
Turnkey utility-scale and grid-scale BESS products paired with energy management software to operate and optimize them.
Key Features: Enterprise Systems, Power Management Software
3. Honeywell
Customizable and scalable utility-grade BESS systems backed by deep expertise in industrial automation and controls.
Key Features: Enterprise Systems, Commercial Systems, Product Manufacturer
4. Siemens Energy
Design-and-build services for complex, integrated energy systems, including BESS solutions for demanding industrial and utility needs.
Key Features: Design Build, Enterprise Systems
Learn more about Siemens Energy
5. Energy Vault
A major storage company offering battery, gravity, and hydrogen storage options alongside advanced software, operations, and consulting services.
Key Features: Gravity Storage, Hydrogen Storage, Enterprise Systems, Configurable
6. Stem
AI-powered energy storage and management software for commissioning, monitoring, optimizing, and controlling clean energy portfolios.
Key Features: Power Management Software
7. ESS, Inc.
BESS systems for enterprise and utilities built on iron flow battery chemistry, designed for consistent output over long durations.
Key Features: Design Build, Enterprise Systems, Commercial Systems
8. RWE
A fully integrated utility with deep experience developing and operating renewable generation, transmission, distribution, and battery energy storage.
Key Features: Integrated Utility, Enterprise Systems
9. Aggreko
Plug-and-play, self-contained BESS rental in a range of sizes, one of the fastest ways to deploy storage for commercial and industrial sites.
Key Features: Plug and Play, Rental, Commercial Systems, Product Manufacturer
10. American Energy Storage Innovations, Inc.
A BESS product manufacturer offering self-contained systems and software with configurable scale options.
Key Features: Configurable, Product Manufacturer, Commercial Systems
Learn more about American Energy Storage Innovations
How to Choose a BESS Company
- Project scale - Match the provider to your size, from C&I to gigawatt-scale utility.
- Hardware vs. software - Some companies build systems, others optimize them; many do both.
- Battery chemistry - Lithium-ion is common, but iron flow, gravity, and hydrogen suit longer durations.
- Delivery model - Choose between product manufacturers, design-build integrators, rentals, and full-service developers.
Frequently Asked Questions
What is a BESS company?
A BESS (battery energy storage system) company designs, manufactures, integrates, or operates systems that store electricity for later use, supporting peak shaving, backup power, renewable integration, and grid services.
Who are the largest BESS providers?
Fluence and Wärtsilä are among the most established utility-scale providers, while companies like Honeywell, Siemens Energy, and RWE bring large industrial and utility experience. Specialists like Energy Vault and ESS, Inc. focus on long-duration storage.
What is the difference between a BESS manufacturer and integrator?
Manufacturers build the hardware (battery enclosures, inverters, controls), while integrators and design-build firms combine components into a complete system tailored to a site. Many leading companies do both.
Looking for a specific use case? See our commercial & industrial and utility-scale guides, or browse all listings.