The energy giant said the typical dual fuel annual bill will rise by an average of 5.3% with the hike taking effect on 17 June.

The price rise is split between an average rise of 4.4% on gas and 6.2% on electricity and Npower cited the rise in wholesale and policy costs behind the move.

As such, a dual fuel direct debit customer will pay £1,230 a year on the new standard tariff.

However, it confirmed over 60% of customers will not be affected by the increase, including those on standard prepayment meters and the safeguard tariff, as well as those who have locked in to a fixed deal.

The ‘Big Six’ energy supplier has also today launched its prize freeze June 2022 tariff for customers affected by the price rise, which will protect users from any potential price hikes over the next four years.

Simon Stacey, managing director domestic markets, said: “Announcing this price change today isn’t a decision we’ve taken lightly. The costs all large and medium energy suppliers are facing – particularly wholesale and policy costs which are largely outside our control – have unfortunately been on the rise for some time and we need to reflect these in our prices.

“Less than half of our customers are on our standard tariff – one of the lowest levels among the larger energy suppliers. We continue to encourage all our customers to look at our range of competitive fixed deals and switch to a tariff that best suits their needs – whether that’s our green product or a short, medium deal, or the market’s longest fix.”

Npower joins in the footsteps of ScottishPower, British Gas and EDF Energy which have all recently announced price hikes for customers.

Stephen Murray, energy expert at MoneySuperMarket, said this is a chunky rise from Npower.

“If you are one of those million, or on a standard variable tariff with another Big Six or emerging supplier, the chances are you’re paying too much for your energy. The message is clear – ignore all the price rise announcements, take matters into your own hands and switch today.

“Switching couldn’t be simpler – the people who engage in the market are reaping the benefits, and the ones who aren’t are paying hundreds of pounds more than they need to. Customers needn’t worry about it being too difficult or too much hassle – it’s a five minute journey on a comparison site and you can save £250 or more straight away.”