# Fourth Power Raises $20M Series A Plus for Thermal Battery Tech
_Fourth Power raised $20M for its innovative thermal battery tech. It aims to provide long-duration, cost-effective renewable energy storage._
**Published:** 2025-09-16
**Source:** https://www.startuphub.ai/ai-news/funding-round/2025/fourth-power-raises-20m-series-a-plus-for-thermal-battery-tech
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Fourth Power, a Cambridge, Massachusetts-based startup, secured $20 million in a Series A Plus funding round. Munich Re Ventures led this Fourth Power funding. This capital will advance the company's innovative thermal battery technology.

The four-year-old company develops thermal batteries designed for long-duration [energy storage](https://www.startuphub.ai/ai-news/funding-round/2025/torus-secures-200m-for-modular-power-plant-deployment/). These systems use superheated liquid tin and argon-filled chambers. Electricity heats carbon blocks, and then thermophotovoltaic cells convert the heat back into power. This technology aims to provide continuous, cost-effective electricity from [renewable energy](https://www.startuphub.ai/ai-news/funding-round/2025/romes-renewcast-secures-e1m-for-ai-renewable-energy-forecasting/) sources.

Fourth Power plans to deliver commercial-scale batteries by 2028. The company is currently designing a 1-megawatt-hour demonstration battery. This new Fourth Power funding supports building its first full-scale battery. The technology projects costs significantly below lithium-ion batteries and natural-gas peaking plants.

## Advancing Thermal Battery Deployment

The thermal batteries offer over eight hours of continuous electricity, double the duration of most grid-scale battery storage solutions. Fourth Power targets a storage cost of $25 per kilowatt-hour at large scale. This represents one-tenth the cost of current lithium-ion alternatives and aims to compete with solutions from companies like Form Energy. The system maintains stable temperatures, losing only 1% of stored energy daily.

Breakthrough Energy Ventures and DCVC also participated in the Series A Plus round. Fourth Power previously raised a $19 million Series A in 2023. This latest Fourth Power funding accelerates its path to market.
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Original analysis from [startuphub.ai](https://www.startuphub.ai), the #1 AI startup directory.