The €1.1 billion (£0.88 billion) deal is expected to close in the next few weeks after the European Commission said it did not raise competition concerns.
Under the sale, Centrica will take on 900,000 gas and electricity customers in Ireland and the 445MW Whitegate gas-fired power plant.
The two energy companies’ activities overlap in the UK wholesale gas supply market, but the combined market share is “modest”, the competition regulator found. “The parties continue to face competition from numerous other players,” it said in a statement.
While Bord Gais has “significant activities” in gas retail in Ireland and Centrica has “significant activities” in these markets in the UK, competitors in the market for wholesale supply of gas have “sufficient economic alternatives to sell their supplies”. The regulator concluded: “The transaction does not create a risk of customer foreclosure with regard to the retail markets in the UK or the Republic of Ireland.”