More than a third of people using pre-pay power meters went without electricity for more than a day because they couldn't afford to top up, while a few went up to a week without power, a survey has revealed.
Just over 300 people on pre-pay meters were surveyed by the University of Otago this year.
Kim O'Sullivan, who led the research, says most people were able to top up their power quickly if it ran out, but 38% said they had gone without it for more than a day.
Ms O'Sullivan told Radio New Zealand's Nine to Noon programme on Monday that just over half of the people surveyed had children and an overwhelming majority were Maori or Pacific Islanders.
The Child Poverty Action group says low income families are sacrificing buying food for their children to pay for electricity. Spokesperson Mike O'Brien says there needs to be a more responsive system for people who can't pay power bills instead of relying on markets to distribute such a fundamental commodity.
Just over 53,000 New Zealand householders use pre-pay meters. Meridian Energy has the biggest market share with 13,000 customers.
The company admits it does cost more to be on a pre-pay meter. However, general manager of retail James Munro said it does save low income families money in the long run.
"What the survey didn't cover is that customers who move onto pre-pay have generally been paying a lot of disconnection fees, reconnection fees, interest and credit fees to their banks or lenders, or worse, loan sharks - and usually the cost of their energy goes down by several hundred dollars."