Tariffs prices. npower charges different rates depending on the region of the country that you live in. Please provide your postcode to view prices for this tariff as well as to compare all other tariffs in the market to see which one is the cheapest for you.lease note that npower Fixed Energy June 2016 is no longer available. Those currently on this tariff may see their prices increase as of 30 June, 2016 as they will be automatically rolled onto 'Standard' tariff prices.