Peak Energy installs a sodium-ion grid battery with no cooling system

WATKINS, Colo., July 2025 — Peak Energy shipped what it calls the first grid-scale sodium-ion storage system in the U.S., a passively cooled battery now running at a Colorado solar test site. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of September 26, 2025)

Outcome: an 875 kW / 3.5 MWh sodium-ion battery at SolarTAC in Watkins, Colorado. (Canary Media) ESS News reported it operating by Sept. 26, 2025. (ESS News)
Cost: not disclosed. The pilot is paid for by Peak, per Canary Media. (Canary Media)
Peak's savings claims: a 20% cut in lifetime cost and 33% lower degradation over 20 years, worth more than $100 million over a project's life. (ESS News)
Status: pilot; Peak expects commercial-scale projects from 2027. (ESS News)

What Peak says it built

Peak's release calls it "the first ever fully passive megawatt-hour scale battery storage system," the largest NFPP system in the world and the first grid-scale sodium-ion system deployed to the U.S. grid. Those are company claims. It says the product is "cost-competitive with state of the industry products" with much lower operating costs. (Peak Energy)

"There's no moving parts, no fans, no liquids, no pumps, no nothing," Cameron Dales, Peak's chief commercial officer and cofounder, told Canary Media. A solid-state heater keeps the cells from getting too cold to charge. (Canary Media)

Why skip the cooling

Lithium iron phosphate (LFP) grid batteries ideally stay within a few degrees of 25°C. "An LFP [energy storage system] is essentially a giant refrigerator that has to operate flawlessly for 20 years in the desert," Dales said. Peak's NFPP cells tolerate minus 20°C to 45°C, Canary Media reported. (Canary Media)

Canary Media says passive cooling cuts materials and up to 90% of auxiliary power use over a project's life, and removes hardware that has itself caused some recent battery fires, for example by spraying water on live batteries. (Canary Media)

"With the lowest operating cost of any storage system in the market today, Peak Energy is proud to have developed a ready-to-deploy answer to energy affordability," said CEO Landon Mossburg; the cost ranking is his claim. (ESS News)

How the pilot works

Nine utilities and independent power producers signed on to get exclusive performance data. If the system meets agreed metrics, they will buy Peak's product, Canary Media reported. Dales described it as a way to avoid "a classic failure mode, to get piloted to death." (Canary Media)

Some consortium members have asked for 10 to 50 MWh demonstration batteries in 2026, and one large developer is working on a 2027 project of nearly a gigawatt-hour for a hyperscaler data center, Dales said. (Canary Media)

The money

Peak emerged from stealth in 2023 with a $10 million seed round and raised a $55 million Series A in 2024, ESS News reported. It aims to break ground on its first domestic giga-scale factory in 2027. (ESS News)

Earlier in 2025, Dales put the passive-cooling savings at "up to $75/kWh on a net present value basis" over 20 years, "more than the cost of the cells themselves"; that is the company's own math. (ESS News)

The China question

The cells were imported from China; Peak designed and built the enclosure in Burlingame, California, and plans U.S. manufacturing of the whole package if the pilot works, Canary Media reported. (Canary Media)

What went wrong

Imported cells. Peak's promise to 'onshore battery manufacturing' still runs on cells from China for now. (Peak Energy; Canary Media)
Small and early. 3.5 MWh, against 100 MW-scale sodium-ion projects already operating in China, per ESS News. (ESS News)
LFP keeps getting cheaper. Sodium-ion still trails LFP on cost-efficiency and performance, ESS News noted. (ESS News)
What we don't know yet: whether the pilot met its metrics, and the system's measured degradation.

Our follow-up question for Peak Energy

Did the SolarTAC pilot meet the consortium's metrics, and when will Peak make its own cells in the U.S.?

Sources

Peak Energy, “Peak Delivers First Grid-Scale, Sodium-Ion Battery Storage System in the U.S.,” July 30, 2025. peakenergy.com
Canary Media, “Peak Energy's new battery is cooler than lithium-ion systems,” Aug. 21, 2025. canarymedia.com
ESS News, “Peak Energy announces operation of first large-scale sodium ion battery in US,” Sept. 26, 2025. ess-news.com

Disclosure: [not in copy] Editor placeholder