The millionaire founder of Ovo Energy is locked in a battle with his investors over control of the company’s £370m technology arm.

Stephen Fitzpatrick is in a standoff with Mayfair Equity Partners and Mitsubishi Corporation to determine the future ownership of Kaluza.

The dispute has emerged following the proposed £600m sale of Ovo’s energy arm to Germany’s Eon, which did not include Kaluza.

Both Ovo’s energy retail business and Kaluza are part of the broader Ovo Group, which counts Mr Fitzpatrick, Mayfair and Mitsubishi among its main shareholders.

All three have so far been united on the sale, which is awaiting regulatory approval after it was announced in May.

However, a spat has emerged over the ownership of Kaluza.

Founded by Mr Fitzpatrick in 2019 as Ovo’s software division, Kaluza was most recently valued at $500m (£370m) and was licensed to other energy companies around the world, such as France’s Engie.

The Telegraph understands that all three shareholders want control of Kaluza but agreed earlier this summer to part ways.

“They are weird bedfellows,” said one industry source. “They can’t get along. They have reached a conclusion that they need to find ways to exit this relationship.”

Mr Fitzpatrick and the investors have exchanged letters on the future of ownership of Kaluza in recent weeks, with two proposals believed to have been discussed.

One involves Mr Fitzpatrick taking control by funnelling the proceeds of the Ovo sale into Kaluza, while the other involves him stepping back in favour of the investors.

However, both sides are questioning the other about whether they have the financial firepower to take Kaluza forwards.

One source suggested Mr Fitzpatrick offered to surrender his position in Kaluza in return for more cash.

He is currently Kaluza’s chief executive after replacing Mel Gander in March 2026.

It is understood that Mayfair, which previously owned restaurant chain Yo! Sushi and haircare brand Tangle Teezer, would be in pole position to take control of Kaluza in the event Mr Fitzpatrick was displaced.

The investment bank Arma Partners was appointed to explore options for Kaluza last year.

All three investors are poised to make hundreds of millions of pounds from the sale of Ovo based on an existing shareholder agreement.

This will significantly increase Mr Fitzpatrick’s personal fortune after he founded Ovo Energy in 2009.

He now owns just under 50pc of the business, meaning he is in line for a potential £300m payday.

Originally set up to challenge legacy suppliers such as British Gas, the Belfast-born former JP Morgan trader turned the business into Britain’s fourth-largest gas and electricity business, serving around four million customers.

However, its growth has not been without challenges, as it previously warned about its ability to stay afloat amid regulatory scrutiny of its finances.

The Telegraph revealed this year that Ovo was cutting tens of millions of pounds in costs under a business plan aimed at securing its survival.

The Eon takeover will not only guarantee Ovo’s future but it will also create the country’s largest energy supplier with a combined 9.6 million customers.

A serial entrepreneur who modelled himself on Sir Richard Branson, Mr Fitzpatrick has also founded a string of other businesses.

They include flying taxi startup Vertical Aerospace and London’s elite private members’ club Kensington Roof Gardens.

His empire previously attracted scrutiny as he funnelled money from Ovo into his other ventures.

MPs grilled Mr Fitzpatrick about £40m worth of inter-company loans in 2022, urging him to “open the books” to shed more light on Ovo’s finances.

As well as selling Ovo, Mr Fitzpatrick also lost control of Vertical Aerospace as part of an emergency rescue deal.

In recent years, he has focused on redeveloping Kensington Roof Gardens, which has involved borrowing more than £75m from various lenders.

This includes a £15m loan subject to an interest rate of 17.5pc.

Mayfair Equity Partners, Ovo and Mr Fitzpatrick declined to comment.