Powering the Future: A Look at the Top 10 Mega Battery Projects in the US for 2025

The US energy storage market in 2025 is undergoing a monumental transformation, defined by a rapid and massive scale-up in Battery Energy Storage System (BESS) capacity. The primary driver is the urgent need to firm up intermittent renewable energy and guarantee grid reliability. Projects are now consistently exceeding 1, 000 MWh, with several proposed developments targeting an unprecedented 4, 000 MWh or more, such as the Darden Clean Energy Project at 4, 600 MWh and Hydrostor’s innovative Willow Rock center at 4, 000 MWh. The dominant theme for 2025 is the strategic deployment of giga-scale storage to create dispatchable, carbon-free power, effectively turning variable solar and wind into dependable, 24/7 assets. This trend is most visible in high-renewable-penetration states like California and Arizona, where these mega-projects are becoming the linchpin of a modern, resilient grid.

1. Darden Clean Energy Project

Company: Darden Clean Energy, LLC
Capacity: 4, 600 MWh
Application: Paired with a 1, 150 MW solar farm to provide dispatchable, carbon-free power to the California grid, enabling energy delivery for hours after sunset and during peak demand.
Source: Darden Clean Energy Project

2. Bellefield Solar and Energy Storage Project

Company: Multiple developers; EQT Exeter is a key landowner
Capacity: Estimated 4, 000 MWh
Application: Designed to function as a virtual power plant, providing large-scale grid services including frequency regulation, resource adequacy, and energy arbitrage to support California’s grid.
Source: Top 7 Battery Energy Storage System (BESS) Projects in the USA …

3. Willow Rock Energy Storage Center

Company: Hydrostor
Capacity: 4, 000 MWh
Application: Utilizes Advanced Compressed Air Energy Storage (A-CAES) technology for long-duration (8-hour) energy storage, enhancing grid stability and supporting high renewable penetration. Supported by a conditional $1.76 B DOE loan.
Source: Massive underground air-battery project lands $1.76 B DOE award

4. Moss Landing Energy Storage Facility

Company: Vistra Corp
Capacity: 2, 500 MWh (as of 2025)
Application: One of the world’s largest operational battery facilities, providing essential grid-balancing services, absorbing excess solar generation, and dispatching power during evening peak hours.
Source: Moss Landing Power Plant – Wikipedia

5. Gemini Solar + Storage Project

Company: Primergy
Capacity: 1, 416 MWh
Application: Paired with a 690 MW solar farm to make solar power dispatchable and reliable, helping to stabilize the grid in the Western U.S. and power over 400, 000 homes.
Source: These Are The States In America Leading The Way In Solar Power …

6. Nighthawk Energy Storage Project

Company: Arevon Energy
Capacity: 1, 200 MWh
Application: A standalone battery facility providing grid stability and capacity, absorbing low-cost renewable energy and selling it back to the grid during high-demand periods.
Source: Two New Projects Add 1.35 GW of Solar-Battery Capacity to …

7. Papago Storage Project

Company: Recurrent Energy
Capacity: 1, 200 MWh
Application: Mitigates Arizona’s “duck curve” by storing excess midday solar power and deploying it during evening peaks, enhancing grid reliability in a region with high air conditioning loads.
Source: Arizona’s largest grid-scale battery is now online – pv magazine USA

8. Eland Solar & Storage Center

Company: Arevon Energy
Capacity: 1, 200 MWh
Application: A hybrid project combining a 400 MW solar array with a 4-hour battery system to provide reliable, clean power to Los Angeles under a long-term power purchase agreement.
Source: Arevon: A Leader in America’s Critical Energy Storage Future

9. Sierra Pinta BESS Project

Company: Bright Night
Capacity: 360 MWh
Application: Specifically engineered to deliver stored power during peak demand periods, providing firm capacity and enhancing grid resilience for approximately 90, 100 homes in Arizona.
Source: Bright Night breaks ground on new Arizona energy center

10. Cranberry Point Energy Storage

Company: Plus Power
Capacity: 300 MWh
Application: The largest standalone battery in New England, ensuring grid reliability during winter peaks, managing natural gas constraints, and supporting the integration of offshore wind.
Source: Careers – Plus Power

Table: Top 10 US Mega Battery Projects (2024-2025)

From Niche Asset to Grid Cornerstone

The diversity of applications across these top projects signals that energy storage has graduated from a niche asset to a fundamental cornerstone of the grid. We are seeing a clear bifurcation in strategy. On one hand, hybrid projects like the Gemini Solar + Storage Project and the Eland Solar & Storage Center are becoming standard for making new renewable generation dispatchable. On the other hand, large standalone facilities like the Nighthawk Energy Storage Project and Massachusetts’ Cranberry Point Energy Storage are being developed purely for grid services and market arbitrage. This proves that storage is no longer just an add-on; it is a versatile, multi-purpose tool that grid operators rely on for everything from frequency regulation to seasonal reliability.

US Battery Capacity Shows Explosive Growth

This chart’s projection of capacity doubling by 2025 visually confirms storage’s rapid shift from a niche asset to a fundamental grid cornerstone.

(Source: Battery Technology)

The Sunbelt’s Storage Supremacy

Geographically, the data reveals the unquestionable dominance of the American Sunbelt. Eight of the top ten projects are located in California, Arizona, and Nevada. This concentration is a direct response to the region’s massive solar build-out, which creates the infamous “duck curve” and makes large-scale storage both technically necessary and economically viable. Ambitious state-level clean energy mandates, particularly in California, have created a powerful market pull for gigawatt-scale projects like the proposed Darden and Bellefield developments. However, the inclusion of the Cranberry Point project in Massachusetts is a key indicator of broadening adoption. Its business case is built on solving different regional challenges—winter peak demand and offshore wind integration—proving that the need for mega-batteries is becoming a national story, not just a Southwestern one.

California and Texas Dominate US Storage

This ranking directly supports the section’s focus on the Sunbelt’s supremacy, showing California and Texas far surpassing other states in installed battery capacity.

(Source: Yes Energy)

Beyond Lithium-Ion: Diversification and Scale

These installations offer a clear snapshot of technological maturity. Standard 4-hour duration lithium-ion systems are the dominant, fully commercialized technology, as proven by the operational scale of facilities like the 2, 500 MWh Moss Landing project and the increasing use of safer lithium iron phosphate (LFP) chemistry in new builds like Nighthawk. However, the most significant trend is the strategic push for technological diversification. The Willow Rock Energy Storage Center is a landmark project, not for its capacity alone, but for its use of Advanced Compressed Air Energy Storage (A-CAES). Backed by a $1.76 billion conditional loan from the Department of Energy, this 8-hour duration facility marks a critical step in scaling non-lithium-ion technologies to meet long-duration storage needs, moving them from demonstration to first-of-a-kind commercial reality.

Forward-Looking Insights: The Road to a Terawatt-Hour Grid

The projects of 2024 and 2025 signal a paradigm shift where energy storage moves from an ancillary service to a core grid infrastructure asset, with sheer scale as the defining characteristic. The ambition demonstrated by projects in the permitting stage, like the 4, 600 MWh Darden facility, provides a blueprint for the next five years. These are not just power plants; they are regional energy hubs designed to function as virtual reservoirs of electricity. Looking forward, the federal backing for technologies like A-CAES confirms that the market is actively seeking alternatives to lithium-ion for longer-duration applications. The industry is maturing on a dual track: hybrid projects will be essential for integrating new renewables, while standalone storage assets will become the primary tool for ensuring overall grid stability and capturing market value. The conversation is rapidly shifting from megawatt-hours to gigawatt-hours per project, paving the way for a truly resilient and renewable-powered grid.

Frequently Asked Questions

What is the largest battery project mentioned in the list for 2025?

The Darden Clean Energy Project is the largest, with a planned capacity of 4,600 MWh. It is designed to be paired with a 1,150 MW solar farm in California to provide dispatchable, carbon-free power.

Why are most of these mega-battery projects located in California and Arizona?

These states are part of the American Sunbelt, which has a massive amount of solar power generation. This creates the “duck curve” problem, where there’s an oversupply of solar power during the day. Large batteries are essential to store this excess energy and deploy it during the evening peak, ensuring grid stability and making renewable energy more reliable.

Are all these projects using the same type of battery technology?

No. While most projects use lithium-ion batteries (often the 4-hour duration type), the article highlights a move towards technological diversification. The Willow Rock Energy Storage Center is a key example, as it uses Advanced Compressed Air Energy Storage (A-CAES) to provide longer, 8-hour duration storage.

What are the main purposes of these large-scale battery systems?

These projects have two primary applications. First, in hybrid projects like the Gemini Solar + Storage Project, they are paired with renewable sources (like solar) to make them dispatchable and reliable 24/7. Second, standalone facilities like the Nighthawk Energy Storage Project are built specifically for grid services, such as providing stability, managing demand peaks, and energy arbitrage (buying low-cost energy and selling it high).

Does the list include any projects outside of the Southwestern US?

Yes. The Cranberry Point Energy Storage project in Massachusetts is highlighted as an important example of broader adoption. Its purpose is to solve regional challenges different from the Sunbelt, such as ensuring grid reliability during winter peaks and helping to integrate power from offshore wind farms.

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