Certain Energy, the British long-duration energy storage company formerly known as RFC Power, has closed a USD 13.62 million Series A funding round and simultaneously announced a rebrand, as it moves to commercialise a manganese-based flow battery technology it says can store clean power for days rather than hours at a fraction of the cost of existing alternatives.

A New Name and a New Chapter

The company, which was founded in 2017 as a spin-off from Imperial College London, has operated under the RFC Power name since its inception. The rebrand to Certain Energy accompanies the funding announcement, which the company made on 26 August 2026.

The capital will be used to scale the technology for volume production, develop a grid-connected MWh-class system in India, expand its research facility in the United Kingdom, and build out the supply chain required to deliver replicable projects across different markets.

Executive Chair Mark Selby framed the fundraising in terms of a specific and growing cost problem facing the British grid. "Last year, the UK Government spent around USD 2.04 billion asking renewable energy providers to shut off their operations during peak production, and left unaddressed, the grid operator expects that to climb towards USD 10.90 billion a year by 2030," he said.

"The answer is long-duration energy storage, and Certain Energy has the technology and now the funding to deliver highly efficient, affordable batteries, based on abundant materials, to make this a reality."

Who Led the Round and Why

The Series A was led by the British Business Bank, which contributed USD 4.77 million of the total. Joining the British Business Bank in the round were Centrica plc, Ceres Power Holdings plc, and Temasek Trust's Catalytic Capital for Climate and Health, known as C3H.

Michael Shanks, Minister of State in the Department for Energy Security and Net Zero, acknowledged the government-backed investment directly. "Homegrown clean energy is our route to more affordable bills and energy security, and storing it for when we need it most is critical," he said.

"By investing USD 4.77 million in Certain Energy, the British Business Bank is backing British innovation and helping develop the long-duration energy storage we need to store clean power for days, not hours, and deliver a more secure energy system."

Charlotte Lawrence, Managing Director and Head of Direct Equity at the British Business Bank, pointed to the technology's potential reach beyond the UK. "Certain Energy's technology has proved it can deliver longer duration storage while reducing costs, with potential applications not only in the UK, but across the globe," she said. "Our investment will help Certain Energy commercialise and take the next steps towards deployment."

Rob Booker, Chief Strategy and Transformation Officer at Centrica, described long-duration storage as critical to managing the future energy system and said Certain Energy's technology is the kind of innovation needed to reduce costs and improve efficiency while supporting a more renewables-led, intermittent power mix.

Stuart Paynter, Chief Financial Officer at Ceres, highlighted the combination of chemistry and manufacturing pathway that attracted the fuel cell company to the deal. "Certain Energy has a combination that is rare in this sector: a low-cost, abundant chemistry and a credible, capital-efficient route to manufacturing," he said.

Ryan Tan, Head of C3H at Temasek Trust, connected the investment to the fund's broader climate mandate. "Certain Energy's novel battery technology replaces traditional battery elements with earth-abundant materials such as manganese to deliver cost-effective and scalable long-duration storage performance with less environmental impact," he said.

The Technology: Manganese as a Foundation

Certain Energy's flow batteries are built around manganese, which the company describes as the twelfth most abundant element in the Earth's crust. The core distinction of a flow battery compared to conventional battery designs is that discharge duration can be extended by increasing the size of the electrolyte tanks, meaning storage can be configured to last from hours to days depending on the application.

The company reports a round-trip efficiency above 75 percent, which it says allows the technology to compete economically with lithium-ion batteries on key grid services, while also supporting the resilience and reserve functions needed by a grid that is increasingly dependent on renewables. The patented electrolyte is designed for a 20-year operating life with minimal capacity degradation.

On cost, the company states that its design and materials have the potential to reduce marginal storage costs to around one-tenth of comparable vanadium flow batteries and to undercut lithium-ion energy storage systems by a significant margin as well.

Vanadium flow batteries represent the most established category in the broader flow battery market, making that cost comparison a pointed one for the sector.

The Market Problem Certain Energy Is Targeting

The company's pitch rests on a structural tension within modern electricity grids. As renewable energy capacity grows, the variability of wind and solar generation creates periods of surplus that grids cannot absorb and periods of shortage that require backup from gas-fired generation.

Long-duration energy storage is presented as the mechanism that can bridge those gaps, allowing surplus renewable power to be stored and dispatched when production falls short.

Chief Executive Officer Tim von Werne articulated the company's positioning directly. "Long-duration storage is the missing piece of the clean energy system, and manganese flow is the technology that should win," he said.

"With the British Business Bank behind us, we have the capital and the mandate to build a global champion here, turning world-class UK science into the industry the energy transition needs."

The company's planned grid-connected MWh-class demonstration in India represents its first major international deployment step, alongside the expansion of its UK research base. Both efforts are intended to demonstrate that the technology can be replicated at scale across different grid environments and regulatory contexts.

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