Charles Berry, the former ScottishPower director, has invested £100,000 in the energy efficiency group Eaga which he chairs, and which jumped 16% on its stock market debut yesterday to give him an instant paper gain of more than £16,000.

The float valued Eaga at £453m, landing windfalls for its employees who owned the social enterprise and held on to 51% of it, and Berry said it could be seen as "the model company of the future".

The Newcastle-based group has installed energy efficiency measures in more than five million homes in the UK, and made a pre-tax profit of almost £20m last year on revenues of £354m.

It installed Berry as chairman 18 months ago, though he held no shares before the listing.

He said: "For me, Eaga is a good company. The things it does make a real difference to people' s lives it started in 1990 with three people and now has 3500, all of whom have a piece of the business.

"If you look at what a lot of people say about the model company for the future, it is where capital markets meet strong employee ownership, and we see that coming through in motivation, commitment and all sorts of ways."

The float placed 105 million shares at 181p, and raised another £30m from 16.6 million new shares to provide funds for further acquisitions in a fragmented market.

The shares closed yesterday at 211p.

Andrew Kitchingman, at house broker Brewin Dolphin, said: "This makes sure they have the firepower for acquisitions along the lines of the ones they have made."

Brewin said the shares had been "oversubscribed at the higher end of expectations".

Eaga says it replaces a heating system every minute of every working day, and delivers energy efficiency improvements, such as loft and cavity wall insulation, in more than 1000 homes every day.

Eaga is a major deliverer of the Westminster government's fuel poverty programmes, though it was ousted from its contract with the Scottish Executive last year by Scottish Gas.

It also works as a contractor for social housing providers and utility companies, and as a central heating service company and insulation installer in the "able to pay" market.

It said one of its objectives on flotation was to "further motivate the employee shareholders of the company by providing them with visibility on the value they have brought to the business".

John Clough, chief executive and co-founder of the business, said: "We were keen to communicate the Eaga story to our investors and are extremely pleased to have received such strong support and establish a high-quality shareholder base.

"Going public will help us to achieve our corporate and social objectives and we look forward to life as a listed company and to being able to take advantage of the many growth opportunities open to us."

Berry commented that he had first met Clough in Liverpool a decade ago when he was running Manweb for ScottishPower.

He said the non-executives had brought their experience of the listed environment - he had been on the board of Thus when it floated and later joined the board of Drax.