Salvation Army officer Amanda Martin said people were already struggling with spiralling food and rent costs.
Higher power prices would only add to their woes, she said.
"They're cutting back on [food] ... buying the cheap, quick-fix food that doesn't give nourishment."
In Rotorua, more than 6000 Genesis Energy customers experienced the largest rise during the period ($133).
Part of this increase was because of a $79 increase in Unison lines charges.
Mrs Martin said higher living costs were causing havoc for many people.
"They're getting themselves emotionally stressed before they even get the bill."
Tiny Mighty Power had the lowest increase in retail charges locally, with customers experiencing no rise during the 12-month period.
In Christchurch, nearly 20,000 Mercury Energy customers were slammed with an average power bill increase of $423 - the country's steepest rise for the period.
The jump was partly because of a $60 increase in Orion NZ lines charges.
Further south, 600 lucky Otago residents saw a drop of $104 in their power bills. The Trust Power customers were with the Network Waitaki lines company.
New Zealand's Electricity Authority said competition between power retailers was key in keeping prices down.
In the past four years, four independent retailers had entered the market, with four others considering entrance, chief executive Carl Hansen said.
Consumer NZ recommended customers "shop around" to ensure they received the cheapest rates.
People should compare plans across different power companies, chief executive Sue Chetwin said.
"If you are not [getting the best power rate] then ring your retailer and say, 'I can get cheaper power elsewhere'."
Customers should switch retailers if their present company refused to match lower rates.
