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.ariff Features. 1  npower Standard rates. 2  Variable rate tariff-energy prices may go up or down. 3  Paper or online billing options available. 4  Pay by Monthly Direct Debit, Quarterly Direct Debit or Pay on Receipt of Bill.