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British Business Bank invests £3.5m into energy storage spinout Certain Energy

Press release 26 August 2026

The British Business Bank has invested £3.5m in long-duration energy storage company Certain Energy, formerly known as RFC Power, as part of a £10m Series A funding round.

Founded in 2017 as a spinout from Imperial College, Certain Energy is a UK champion in long-duration energy storage (LDES). The company was established to build battery stores to harvest clean energy and use it to stabilise energy grids, reducing reliance on gas peaker plants.

The round included investment from Centrica Energy, Ceres Power Holdings plc (“Ceres”), and The Temasek Trust’s Catalytic Capital for Climate and Health (“C3H”).

This investment is the latest in the Bank’s extensive support for UK university spinouts. The Bank has supported almost a quarter (24%) of spinout deals in recent years, reflecting its focus on backing the UK’s innovative, IP-rich businesses.

Clean Energy is one of the Government’s eight Industrial Strategy sectors. The Bank is increasing its investment into the sector, with recent investments including Kraken Technologies, tem, Iceotope and Tokamak Energy.

Certain Energy’s patented design both reduces costs and delivers longer storage than alternative batteries. The company’s flow batteries are built on manganese, the twelfth most abundant element in the Earth’s crust, which allows for storage of days rather than hours, and can reduce storage costs to around one tenth of current levels. This allows the company to compete economically with lithium-ion batteries on key grid services, while also supporting the reserve functions needed by an increasingly renewables-heavy grid.

The funding will be used to commercialise Certain Energy’s technology and prepare it for deployment. The company plans to develop a grid-connected system in India, expand its research facility in the UK, and to create the supply chain needed to deliver replicable projects.

Mark Selby, Executive Chair of Certain Energy, said,

The renewable power market is held back by its vulnerability to external factors. Last year, the UK Government spent around £1.5 billion asking renewable energy providers to shut off their operations during peak production, and left unaddressed, the grid operator expects that to climb towards £8 billion a year by 2030. The answer is long duration energy storage and [XXX] has the technology and now the funding to deliver highly efficient, affordable batteries, based on abundant materials, to make this a reality.

Energy Minister Michael Shanks, said,

Homegrown clean energy is our route to more affordable bills and energy security, and storing it for when we need it most is critical.

By investing £3.5 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, said,

With grid demand and supply becoming increasingly volatile worldwide, the financial and strategic value of long-duration energy storage is clear. Certain Energy’s technology delivers a compelling return on investment whilst reducing overall energy needs. This funding will support the team in commercialising their solution and accelerating its deployment.

Further Information

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Notes to editors

About the British Business Bank

The British Business Bank is the UK government’s economic development bank. Established in November 2014, its mission is to drive economic growth by helping smaller businesses get the finance they need to start, scale and stay in the UK. Its remit is to design, deliver and efficiently manage UK-wide smaller business access to finance programmes for the UK government.

In 2025/26 1 , the Bank supported UK smaller businesses to access £9.4bn of finance, made up of £1.3bn of public funding, £4.3bn of private capital crowded in by the Bank and £3.7bn of lending the Bank guaranteed. The funding benefited 38,000 UK businesses, including around 30,000 businesses the Bank had not previously helped to fund.

British Business Bank plc is a public limited company registered in England and Wales, registration number 08616013, registered office at Steel City House, West Street, Sheffield, S1 2GQ. It is a development bank wholly owned by HM Government. British Business Bank plc and its subsidiaries are not banking institutions and do not operate as such. With the exception of BBB Investment Services Limited they are not authorised or regulated by the Prudential Regulation Authority or the Financial Conduct Authority. BBB Investment Services Limited is authorised and regulated by the Financial Conduct Authority. A complete legal structure chart for the group can be found at british-business-bank.co.uk.

The above transaction is operated by British Patient Capital Limited, a wholly owned commercial subsidiary of British Business Bank plc.

British Patient Capital Limited is registered in England and Wales with company number 11271076, and registered office at Steel City House, West Street, Sheffield, S1 2GQ. British Patient Capital makes commitments and invests on its own behalf and on behalf of third-party investors whose investments British Patient Capital manages.

About Certain Energy

Certain Energy (formerly RFC Power) is a UK long-duration energy storage company developing a manganese-based flow battery designed to deliver affordable, reliable energy storage from hours to days to weeks. Founded on research from Imperial College London, it is building a digital-first engineering capability to design, test and scale at pace.

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