As utilities face surging demand from electrification and the advancement of artificial intelligence, Fourth Power, a flexible-duration energy storage provider, has secured $20 million in Series A Plus funding. Led by Munich Re Ventures, with follow-on investments from DCVC and Breakthrough Energy Ventures, the funding will accelerate the commercial deployment of Fourth Power’s modular, utility-scale thermal energy storage system. The funding will support commissioning of an integrated 1 MWh-e demonstration using full-scale commercial components and is the company’s final step before customer deployments. Additionally, this capital will be used to deepen partnerships with suppliers and customers further and grow the customer pipeline.
“We’re in a race between the growing need for reliable electricity and the grid’s ability to provide it quickly and affordably. Existing solutions are too slow to deploy, too expensive for customers, and oftentimes both,” said Arvin Ganesan, CEO of Fourth Power. “Fourth Power offers a new path forward: scalable, flexible-duration energy storage built from abundant domestic materials. It’s how we deliver reliability at a price point that works—for energy providers, their customers, and the future of the grid.”
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Since its $19 million Series A in 2023, Fourth Power has doubled its team size and achieved breakthrough engineering milestones that validate its commercial readiness. The company constructed three large-scale, accelerated life test rigs to validate the durability, safety, and lifetime performance of its subsystems at temperatures up to 2400°C. Further advances include demonstrating a self-lubricating graphite pump for moving molten tin, high-pressure-rated graphite fittings for liquid metal containment, and a scalable inert gas enclosure system.
“Fourth Power is solving a grid problem that’s very real and very near-term, and they’re doing it with a system that’s safer, cheaper, and dramatically more scalable than anything we’ve seen in this category,” shares Peter Ortez, principal at Munich Re Ventures. “We focus on companies tackling the biggest risks facing society. And we believe Fourth Power’s approach represents exactly the kind of resilient infrastructure investment the energy transition demands.”
A principal breakthrough of Fourth Power’s technology lies in its architecture. The thermal energy storage system converts electricity into heat using 2400°C liquid metal as a heat transfer fluid. It then stores that energy in carbon blocks and converts it back to electricity using proprietary thermophotovoltaics (TPVs). The company’s use of very high-temperature liquid metal for heat transfer achieves unprecedented power density, dramatically reducing overall system costs. Fourth Power’s modular design separates power and energy, allowing utilities to add storage duration over time as needs change at just a fraction of the initial installation cost. This flexibility, enabled by storage costs of less than $25/kWh-e, allows Fourth Power’s customers to grow with the grid, a key differentiator from lithium-ion batteries, where adding duration means duplicating the entire system.
“Fourth Power’s modular approach solves the fundamental challenge utilities face: how to build storage infrastructure that adapts as grid conditions evolve,” said Rachel Slaybaugh, partner at DCVC. “What excites us about the next phase is seeing their technology move from laboratory validation to commercial readiness.”
“This technology doesn’t just incrementally improve on existing solutions, but completely reimagines how we approach the problem,” said Carmichael Roberts of Breakthrough Energy Ventures. “With energy demand rising rapidly, we need storage technologies that can scale cost-effectively alongside that growth. Fourth Power’s flexible-duration approach is that kind of infrastructure-grade solution.”
With utilities across the country facing capacity shortfalls and aging infrastructure, Fourth Power’s commercial timing aligns with urgent grid modernization needs. The company expects to announce its first commercial partnerships by 2027. To learn more about Fourth Power’s thermal energy storage system and how the company works to power the world with reliable, low-cost energy, visit gofourth.com.
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