It said the company, which mainly operates in the UK but also does business around the world, will form part of its new international distributed energy and power business.
ENER-G Cogen has 1,400 generating units under contract with a combined capacity of 500MW.
Chief executive of Centrica Iain Conn said: “We are building an international distributed energy and power business, as demand for CHP products and other distributed energy technologies grow. This acquisition strengthens our delivery capability, both in the UK and internationally.”
Last month Centrica revealed the acquisition of Danish firm Neas Energy for £170 million, saying it would pump a further £30 million into the business.
Centrica unexpectedly sold off £700 million of new shares in the first week of May. It said around £350 million of the proceeds would be used to fund two acquisitions, one of which was Neas Energy, with the rest going to pay off debts.
Shares in Centrica fell by around 10 per cent in response to the surprise sale. Analysts at Jefferies said: “Given that neither of these deals could in any way be described as transformational for the group as a whole and won’t move the needle in terms of financial results, shareholders would be justified in asking whether the damage to the share price and management credibility was remotely worth the effort. And the answer, in our view, is an unambiguous – no.”