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.
Ofgem said it would study the estimates Ovo gave to its customers over energy use during the winter of 2016-17.
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.
In a statement, Ofgem said: “The investigation will examine whether Ovo Energy breached licence conditions related to giving customers consumption information that is accurate, or based on a best estimate, complete, and not misleading.
“Incorrect consumption figures can lead to customers receiving inaccurate bills, annual statements and other important information.
“This in turn can lead to customers being unable to properly manage their accounts and deciding to switch based on incorrect information.”
Ofgem added that the opening of the investigation did “not imply that we have made any findings about non-compliance by Ovo Energy”.