The Federation of Family Budgeting Services believes many families will find power price increases hard to cope with, even though they are small.
The Commerce Commission has set out the new maximum prices that power distributors could charge for the next five years beginning on 1 April next year.
Power prices could rise by up to $7.50 a month in Northland, central Hawke's Bay and South Canterbury.
However, lines companies would be allowed to charge less in Wellington, Otago, Central Otago, Tasman and in the King Country.
The federation's chief executive, Raewyn Fox, said the increases were small, but significant.
"Seven dollars a month is gonna be a couple of loaves of bread and a bottle of milk they're not going to be able to buy. It doesn't seem much, but when you're already really struggling even a dollar is something that you have to find."
Ms Fox said one positive was the fact that prices must stay below the rate of inflation.
Commerce Commission deputy chair Sue Begg said the new pricing struck the right balance to keep suppliers from earning excessive profits, while ensuring they had adequate revenue to meet quality and reliability standards.
Electricity distributors said they were generally happy with the new pricing.