Shares in Carillion were up on the FTSE 250 in morning trading after the construction company said it had agreed terms to acquire green outsourcing company Eaga.
Under the deal Carillion will pay 120 pence per Eaga share, valuing the company at £306.5 million.
Carillion said it expected synergies of nine million pounds by the end of 2013, with one off costs of around £15 million.
The acquisition still needs to be approved by Eaga shareholders, the Financial Services Authority and the High Court of Justice.
Philip Rogerson, Chairman of Carillion, said, "The acquisition brings together two complementary companies, enhancing Carillion's position as one of the UK's leading support services companies. The acquisition is expected to be immediately earnings enhancing and builds on Carillion's previously announced objectives for growth.
"Carillion has identified the low carbon market as a strategic area of growth and the acquisition of Eaga will create a scalable platform to build the UK's largest independent energy services provider. This will also extend Carillion's capability to provide integrated support services solutions for its existing customers, for whom energy services are an increasingly important requirement."
Charles Berry, Chairman of Eaga, commented, "The offer received from Carillion has come at an interesting time in Eaga's development, as our markets are changing rapidly. While there are exciting future prospects, we believe these are potentially better accessed as part of a larger group.
"Carillion offers our unique business the opportunity to grow in a strong home, it offers our Partners the prospect of delivering that growth potential, while our shareholders receive a significant cash premium and a partial share alternative which allows them to participate in the Enlarged Group's future potential."
10:35 shares in Carillion were up 1.40 per cent on the FTSE 250 to 390.60 pence per share.