Energy supplier npower will increase average domestic prices by 5.8% for electricity and 5.2% for gas.
Electricity prices will not rise until 1 April, whereas gas prices will go up from 1 February. Small business customers will experience a similar increase.
Andrew Duff, chief executive of RWE Innogy, npower's parent company, says the increases reflect a rise in wholesale energy market costs, which have risen by 20% year-on-year.
Duff says other factors are the rise in gas transportation costs, which will go up by 5% this year; renewable energy obligations; and energy efficiency programme costs.
The increases amount to around 29p per week for the average domestic electricity user and 34p per week for the average domestic gas user, based on an average annual residential usage of customers on standard domestic tariffs of 3,300kWh for electricity and 20,500kWh for gas.
