Can Rust Power Grid Scale Energy Storage for 100 Hours?

When Lithium Batteries Run Out of Time

Renewable energy faces a critical timing problem. Solar panels generate power during sunny afternoons. Wind turbines spin when weather conditions permit. Yet electricity demand peaks during evenings when solar stops producing. Lithium-ion batteries bridge this gap for about four hours before running empty. The grid scale energy storage challenge demands longer solutions.

 Form Energy addresses this with technology that sounds almost too simple—controlled rust. Their iron-air battery system stores electricity for 100 continuous hours. Multiple utility deployments across America begin operations throughout 2026. This marks the transition from laboratory promise to working infrastructure.

The Chemistry Behind Controlled Rusting

The iron air battery operates through a process everyone recognizes but few consider useful. During discharge, metallic iron pellets react with oxygen from surrounding air and water from the electrolyte solution. This creates iron hydroxide, commonly known as rust, while releasing stored electricity. Charging reverses everything. Excess grid electricity flows back through the battery. 

The rust converts back to metallic iron. Oxygen and water separate out. This reversible rusting cycle repeats thousands of times without significant degradation. Each module resembles a standard washer-dryer set in size. Inside sit stacks of approximately 30 meter-tall cells filled with iron powder. The system uses non-flammable water-based electrolyte instead of volatile organic solvents. No rare-earth metals appear anywhere in the design. Form Energy sources roughly 80 percent of components domestically within the United States.

Five Major Projects Go Live in 2026

Form Energy's West Virginia manufacturing facility completed trial production in September 2024. Commercial production started by year-end. Now 2026 brings multi day energy storage from concept to reality across five states. Xcel Energy operates two separate 10 MW/1 GWh systems in Minnesota and Colorado. Georgia Power activates a 15 MW/1.5 GWh installation, currently the largest announced iron air battery project globally by energy capacity. Pacific Gas & Electric brings online a 5 MW/500 MWh system in northern California's Mendocino County, backed by $30 million from the California Energy Commission. New York deploys a 10 MW/1 GWh demonstration project supported by NYSERDA funding. These installations provide enough capacity to power approximately 1,500 homes for four complete days per system. Utilities use them primarily for grid resilience during extreme weather events and renewable energy balancing.

Economics That Challenge Lithium Dominance

Traditional lithium-ion systems cost approximately $130-$150 per kilowatt-hour when including packaging, cooling, and fire suppression equipment. Form Energy targets under $20 per kilowatt-hour at commercial scale. This dramatic cost reduction changes what becomes economically feasible. The trade-off involves efficiency. Iron air battery systems achieve about 60 percent round-trip efficiency compared to lithium's 90 percent. However, duration matters more than efficiency for renewable energy storage spanning multiple days. A battery that stores electricity cheaply for 100 hours enables wind and solar to function as baseload power. Grid planners no longer need natural gas peaker plants for backup during windless, cloudy periods. Form Energy secured $405 million in Series F funding during January 2026. GE Vernova joined as both investor and strategic partner. The Department of Energy awarded up to $150 million for manufacturing expansion. Factory capacity reaches 20 GWh annually by 2027. By 2028, Form Factory 1 will employ at least 750 workers across over one million square feet of manufacturing space.