About 1.4 million Npower customers will be hit with average price hikes of 9.8% - or £109 per year – from 16 March.
This is made up of a 4.8% gas increase and a 15% electricity rise.
The move affects customers on a standard variable tariff – excluding pre-payment customers (those who pay for their energy in advance using a meter).
However, approximately 80,000 customers who receive a ‘Warm Home Discount’ won’t see the price hikes take effect until May.
Npower’s fixed-rate energy customers will not be affected.
- Use our cheap energy tool to see if you can ditch and switch
The Big Six energy provider says it last upped its prices in October 2013. This time round it blames rising wholesale prices and the increasing cost of delivering government policies, such as smart metering and renewable obligations, for the rise.
Simon Stacey, managing director of domestic markets at Npower, says: “This is a hugely difficult decision, and we’ve delayed the date this takes effect until after the coldest months of the year.”
He adds: “We’re already delaying the impact of the increase for vulnerable customers, but anyone who is struggling with their energy bills should contact us straight away to discuss whether they’re on the right tariff for their needs, energy saving help and bespoke payment plans.”
Check if you can switch and save
Energy experts warned in December that households should consider switching due to rising prices predicted for 2017.
Stephen Murray, energy expert at comparison site MoneySuperMarket says: “Standard customers continue to pay over the odds for their gas and electricity and whether you’re an Npower customer or with any other supplier on a standard tariff, the message is and has been clear for a while – switch tariff to a cheaper fixed deal and take control of your energy bills.”
What are other energy providers doing?
- British Gas – In its words, bills will “remain unchanged” until “at least the end of March 2017”. This freeze applies to those on its standard variable tariff, including prepayment customers.
- E.on – Its price freeze is in effect until “at least” April 2017. The freeze applies to those on its E.on EnergyPlan, which is its standard variable tariff. This also applies to its prepayment customers on a standard variable tariff.
- SSE – Has frozen standard variable prices until April 2017 – a move which also applies to its prepayment customers.
EDF meanwhile cut gas bills by up to 12.9% from 6 January, but is upping electricity prices by up to 8.4% from 1 March.
Scottish Power is the last of the big six to play its cards.