Rotorua Contact Energy customers with Unison lines company suffered the biggest price rise of $243 over the past year - a 10.3 per cent increase in retail power costs from August 2012.
This included a $38 increase in lines charges.
At the other end of the spectrum, Just Energy customers with Unison lines company enjoyed a $41 drop in power prices, despite a $38 increase in Unison lines charges.
The study, which relied on Electricity Authority data, was based on an average household using 8000kWh per annum - close to the nationwide average residential consumption.
The general increase in electricity costs comes at a time when many local residents are struggling to make ends meet.
According to the New Zealand Federation of Budgeting services, 2815 Bay residents sought budgeting advice in the year to June. The average client was about $25,500 in debt.
Grey Power has just negotiated a cheaper power deal for its 64,000 national members by forming Grey Power Electricity, in partnership with Pulse Energy - the parent company to Just Energy.
The deal, launched in September, gives Grey Power members access to low-cost power and easy-to-read bills.
Rotorua Grey Power president Rosemary MacKenzie said pensioners had been struggling with rising power prices for a long time but the latest increase would be tough.
Grey Power's deal would save members money, without locking them into long-term contracts.
"[Prices for members] aren't going to increase for the next five years, but should the power price fall, then the price to the consumer will be reduced as well. It's pretty exciting."
It was a lot better than getting the "inevitable" letter from the power company every six months saying prices were going up again, she said.
"People are starting to realise that Grey Power has got something going for it. If we can force the big boys, who are now suddenly coming out of the woodwork with these deals ... if they can do it now, why couldn't they do it before?"
Electricity Authority data show 19,245 households had their power disconnected in the first half of this year alone.
"That equates to 106 households having their power cut off every day, or four every hour," Labour leader David Cunliffe said.
"This is significantly higher than the same time last year and means disconnections for 2013 are likely to exceed 2012 when the number hit 40,000."
Meanwhile, Energy Minister Simon Bridges has come under fire, accused of burying bad news about rising power prices for the previous quarter.
In the three months to May the cost of power for the average New Zealand household rose by 2.2 per cent, adding almost $50 to the annual bill.