The archive · Climate & Energy · Product decision · 2018–2026
Antora's thermal-battery bet: 5 GWh POET plant on-line, then a $550M Series C
Antora turns cheap wind into heat stored in carbon blocks; its first commercial 5 GWh system at POET went live in 2026, then came a $550M Series C.
Antora Energy
What the business is
Antora Energy is a San Jose, California company that builds modular thermal batteries — insulated blocks of solid carbon heated with low-cost electricity — that deliver round-the-clock heat or power to industrial plants, data centers and the grid.
Starting capital：$550M Series C co-led by G2 Venture Partners and Eclipse (July 2026); total corporate and project financing roughly $1B, including a $150M round in 2024
How it started
Founded around 2018 by Andrew Ponec and Justin Briggs, Antora launched its first pilot in 2023: a 5 MWh system at utility Wellhead Electric's facility near Fresno, California. Months later it raised $150M and opened its San Jose factory, betting that making thermal batteries in volume — not exotic materials — would let it deploy faster than conventional storage.
What happened
On May 19, 2026, POET and Antora announced commissioning of Antora's 5 GWh, multi-day thermal energy storage system at POET's Big Stone City, South Dakota biofuel plant — its first commercial-size deployment. Built in under 12 months with more than 200 factory-built modules, the system converts surplus wind power into steam for ethanol production under a long-term heat offtake agreement, and will be fully operational later in 2026; once complete it will rank among the world's largest storage projects. Grok Ventures provided project-level financing as sole external investor. Two months later Antora closed a $550M Series C co-led by G2 Venture Partners and Eclipse, with new investors including Ribbit Capital, Salesforce Ventures, Activate Capital and John Doerr, to build a second US factory and fulfill signed agreements with hyperscalers and industrial customers.
No ending yet — it is still running.
Background
Antora Energy, founded around 2018 in San Jose, California by Andrew Ponec and Justin Briggs, builds modular thermal batteries that store low-cost electricity as heat in insulated blocks of solid carbon. Its bet is that industry and data centers will buy stored heat, not just electrons: the same factory-built module can drive a chemical plant, a food producer, a steelmaker or a data center, without critical minerals or multi-year construction timelines.
Antora proved the concept with a 5 MWh Fresno pilot in 2023, then raised $150M and opened its San Jose factory. On May 19, 2026 it hit the commercial milestone: POET and Antora announced commissioning of a 5 GWh, multi-day thermal storage system at POET's Big Stone City, South Dakota ethanol plant — Antora's first commercial-size deployment. Built in under 12 months with more than 200 modules, the system charges on surplus wind power and delivers steam to the plant under a long-term heat offtake agreement; it will rank among the world's largest storage projects when fully operational.
The project is also a rate-design experiment: Antora and utility Otter Tail Power created a tariff, approved by the South Dakota Public Utilities Commission, that lets the system charge only when local renewables are surplus. In July 2026 Antora closed a $550M Series C co-led by G2 Venture Partners and Eclipse — with Ribbit Capital, Salesforce Ventures, Activate Capital and John Doerr among new investors — bringing total corporate and project financing to roughly $1B, to fund a second US factory and more large-scale projects.
What has to be true
- Industrial process heat is a huge market electricity hasn't penetrated, and thermal batteries convert cheap surplus power into the exact form factories already buy — steam — without grid upgrades.
- Carbon blocks need no lithium, cobalt or rare earths, so Antora's supply chain and manufacturing scale faster than battery chemistry startups.
- Multi-day duration lets thermal storage serve ethanol plants and data centers around the clock, positioning Antora against gas boilers rather than four-hour lithium batteries.
- The Otter Tail tariff turns intermittent surplus wind — normally a grid liability — into a revenue stream, giving utilities a reason to support the technology.
- POET's 12-month deployment timeline proved the 'speed to energy' argument: modules are factory-built, so projects don't wait years for construction.
What can be applied
Sell the energy form buyers already use: Antora won its first customer by delivering steam, not electrons, and paired the hardware with a tariff that only charges when power is cheap and surplus.
Aftermath
As of July 30, 2026, Antora's Big Stone City system was delivering energy to POET and expected to reach full operation later in 2026, with Grok Ventures having provided the project financing. The $550M Series C was earmarked for a second U.S. manufacturing hub, more large-scale projects and a growing pipeline of signed agreements with hyperscalers and industrial companies; the company said it was also developing power-sector projects five to ten times the size of Big Stone to bring data centers online faster.
Sources
- Antora and POET Commission 5 Gigawatt-Hour Thermal Battery Project to Power South Dakota Industry with Affordable Energy
- One of world's largest energy storage plants launches in South Dakota
- Antora Closes $550 Million in Series C Funding to Meet Surging Energy Demand and Reindustrialize America
- Antora snags $550M for heat batteries to run data centers and factories
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