The two businesses will merge together and trade under the So Energy brand. ESB said the move gives the new company the resources and expertise to accelerate growth and invest in new systems, services and products for customers to help them transition to net zero living.

So Energy was founded in 2015 and supplies 100% renewable electricity to 230,000 homes across England, Wales and Scotland.

ESB Energy entered the UK market in 2018 and is part of ESB, Ireland’s largest energy company which operates through a portfolio of brands including ESB Networks, Electric Ireland, ESB International, NIE Networks and ESB Energy.

The acquisition will add ESB Energy GB’s domestic customers to So Energy’s existing portfolio. This will grow So Energy’s customer base by 35% to 310,000 customers.

So Energy customers won’t see any changes to their bills, whilst ESB Energy domestic energy supply customers will migrate to the So Energy brand.

The companies said the partnership will benefit from both companies’ “customer-centric values and green credentials”, ESB’s extensive resources and expertise, and So Energy’s brand.

Both companies already supply 100% renewable electricity, and So Energy has recently launched a solar and battery storage solution for customers.

Monica Collings, managing director of ESB Energy, said: “Building on our track record of investing more than £2bn in UK green energy infrastructure over the past three decades, this latest acquisition will enhance our customer offering and growth opportunities in the UK energy supply market.

“It’s our ambition to build on the success So Energy has achieved in a very competitive market, but one we are confident has excellent potential for our business. We welcome the So Energy team to ESB and look forward to building a strong and reliable brand, offering a suite of net zero focused customer propositions in the years ahead.”

Simon Oscroft, co-CEO and co-founder of So Energy, said: “This new, supercharged So Energy now has the backing and resources to become the next big green energy supplier in the UK. We wanted a partner that shared our values and vision to scale our business in a sustainable way, and develop more industry leading net zero solutions for our customers.

“ESB’s resources, strong heritage and significant UK green energy investments – including their EV charging infrastructure and wind generation portfolio – will enable us to do this. I would also like to wholeheartedly thank our shareholders who have helped us on the So Energy journey so far.”