The UK's Energy regulator is to look into whether Ovo Energy has given inaccurate information to its customers over how much energy they have used.
The regulator said incorrect consumption figures could lead to customers getting inaccurate bills.
Ovo Energy said: "We have a great track record in customer service and are always open to ways to improve it."
Ovo is one of the UK's smaller energy companies seeking to take on the dominance of the "big six" energy firms.
The company was founded in 2009, and currently has about 800,000 customers.
BBC News.