Certain Energy raises £10M Series A to prove manganese flow batteries at grid scale

Certain Energy (London) — formerly RFC Power — has raised £10 million (approximately €11.6 million) in a Series A round led by the British Business Bank, with strategic participation from Centrica, the UK energy major; Ceres Power Holdings, the company's former parent; and Temasek Trust's C3H, the Singapore-based Catalytic Capital for Climate and Health fund. The company simultaneously announced its rebrand from RFC Power to Certain Energy. Founded in 2017 as an Imperial College London spinout, Certain Energy designs and manufactures manganese flow batteries for grid-scale energy storage.

The core technology differentiator is the electrolyte. Flow batteries store energy in liquid electrolytes pumped through an electrochemical cell; the dominant commercial form — vanadium flow — uses vanadium dissolved in sulphuric acid. Certain Energy's system uses manganese instead, a material abundant enough that, at scale, the company projects electrolyte costs at a tenth of vanadium equivalents. The designed operating life is 20 years — significantly longer than the 10-12 year depreciation cycle typical of lithium-ion grid installations.

Why chemistry matters at this stage

The economics of long-duration grid storage are governed by two variables: capital cost per kilowatt-hour and cycle life. A battery that lasts twice as long with significantly lower materials cost amortises over a longer period with fewer replacement events — the arithmetic is straightforward. Manganese flow's challenge has historically been cycle stability at grid-relevant discharge rates: vanadium flow batteries are well-proven in commercial installations, while manganese systems have shown electrolyte degradation that can undermine the long-life claim. Certain Energy's Series A is explicitly structured around proving that stability in a real operating environment.

The capital goes to building a grid-connected MWh-class demonstration system in India — a market where grid instability is an active commercial problem with paying customers, not a policy aspiration — alongside expanding the UK research facility and developing the supply chain for replicable projects.

The investor map

The British Business Bank leads as a government-backed development finance institution. Earlier this month, the BBB's UK Sovereign AI Fund made its first publicly disclosed investment in Callosum, a London AI infrastructure company, at seed stage. Certain Energy's Series A comes through a separate BBB vehicle — the two investments are different programmes — but the breadth of early-stage infrastructure mandates across AI compute and clean energy storage, compressed into a single week, points toward a coherent industrial policy posture rather than opportunistic dealflow.

Centrica is the round's most commercially specific signal. As a major grid-connected UK energy company, Centrica operates storage assets and has direct knowledge of what a 20-year flow battery replacing a conventional peaker plant is worth at the grid dispatch level. An energy major's strategic investment in a storage startup is not equivalent to a purchase order, but it is more than a financial return argument.

Ceres Power Holdings — a UK hydrogen fuel cell company and Certain Energy's former parent — retaining its position through the RFC Power-to-Certain Energy rebrand is notable. A former parent exiting on a fundraise is the more common outcome; staying invested signals that Ceres views the manganese flow technology as compatible with rather than competing against its own fuel cell roadmap.

Temasek Trust's C3H adds a development-finance dimension consistent with the India project: C3H's patient capital mandate aligns with multi-year demonstration timelines in emerging markets where grid reliability is both a national priority and a commercial opportunity.