The FTSE 100 firm requested a judicial review over a decision by Ofgem to change the dates within which wholesale energy prices are used to calculate the price cap.
Centrica said this last-minute change underestimated the cost of supplying energy over the last winter period, resulting in the higher one-off cost.
The company welcomed the judgement, saying it underlined “the importance of transparent and rigorous regulatory processes to ensure well-designed regulation that is in the interest of a well- functioning energy market”.
Centrica added that it will now work with the government and Ofgem to develop future energy policy for its customers.
In late-afternoon trading on Wednesday, Centrica’s shares were 2% lower at 73.3p.