Imagine a battery made not of expensive chemicals but of solid carbon blocks, heated until they glow white-hot. That is exactly what Antora Energy has built — and investors just poured $550 million into scaling it up.
The San Jose-based startup announced its oversized Series C funding round on July 30, 2025, drawing co-leads from G2 Venture Partners and Eclipse, with additional backing from Ribbit Capital and Salesforce Ventures. The round was oversubscribed, meaning more investors wanted in than the company had planned to accept. It adds to a string of successful fundraising, including a $150 million Series B in 2024 led by Decarbonization Partners.
Antora's technology tackles one of renewable energy's biggest headaches: what happens when the sun sets or the wind stops blowing? Solar and wind farms produce electricity when nature cooperates, but power grids need energy around the clock. Traditional lithium-ion batteries — the kind found in electric cars and home storage systems — typically hold energy for only two to four hours. That is enough for daily balancing acts but falls short for heavy industries like steelmaking or chemical plants, which need heat and power for much longer stretches.
Antora's "hot blocks" solve this by storing renewable electricity as thermal energy in thick carbon bricks. When the grid has excess power — say, a windy night when demand is low — Antora's system uses that electricity to heat its carbon blocks to extreme temperatures. The bricks stay insulated and ready, releasing heat on demand either for industrial processes or to generate electricity whenever it is needed. One charge can deliver power for ten hours or more, far outlasting conventional batteries.
The company traces its roots to support from the US Department of Energy. In 2019, Antora received a $7.9 million award from ARPA-E, the DOE's arm for breakthrough energy research. ARPA-E officials were enthusiastic about what they saw. "Antora's American-made thermal batteries represent a breakthrough in energy storage, storing energy as heat in blocks of solid carbon — a low-cost, earth-abundant storage medium with robust US supply chains," the agency noted in a 2024 recap. That year, Antora also secured a $14.5 million SCALEUP grant from the same office, aimed at pushing promising technologies toward commercial use. Part of that funding supports a pilot project with Con Edison, New York City's utility, to explore decarbonizing its vast underground steam system.
The timing matters. After years of rapid growth, the renewable energy transition has faced headwinds from shifting federal policies. Yet clean tech startups like Antora continue attracting capital, suggesting investors see real promise in solutions that can replace fossil fuels across heavy industry.
With $550 million fresh in its accounts, Antora plans to expand manufacturing of its modular battery blocks, which can be deployed at factories, data centers, and power grids alike. The goal is straightforward: store cheap, clean electricity when it is abundant and dispatch it whenever industries need heat or power — without burning a single extra lump of coal or drop of oil.