Single-figure temperatures experienced at the weekend - the coldest "high" was 5.6degC in Queenstown on Sunday - boosted Otago power consumption to a peak of 910MW on Sunday, up from previous weekend's 861MW, Transpower figures show.
Those temperatures, combined with power price rises effective from April 1 of between 2.4% and 10.4% in Otago, meant households were facing escalating power bills.
Electricity retailer Powershop estimated Dunedin households would face average power bill increases of $58 for the three months of this winter.
Figures from Powershop, which increased its prices by about 10% across Otago, show an average-sized household in Dunedin could face a bill of $779 from June to August.
The average increase was slightly less than Auckland's $64, while it estimated some Christchurch residents would face a $90 increase.
Budgeting services said although most power prices went up in April, families would feel their true effect over winter.
Dunedin's Anglican Family Care director Nicola Taylor said the service was seeing people without the most basic living necessities - in one case a family was using an open kitchen oven as a source of home heating.
"That's how desperate it gets.
"As the cold bites, that is when the power bills go up and low-income families do not have enough money to go around."
Its budget service was under "tremendous pressure" meeting its annual Government client target in six months and now had a three-week to four-week waiting list.
"People are struggling with their bills already - even another $30 is going to make it really hard for some people," said Federation of Family Budgeting Services chief executive Raewyn Fox.
"There have been constant increases for five years or more. And it's a period when wages haven't gone up to the same extent."
Grey Power national president Roy Reid said many older people had dinner and went straight to bed to try to keep warm.
"It's a false economy really, because they might do that, but then the house gets cold, and they will get other illnesses because they are cold."
Consumer NZ chief executive Sue Chetwin said people should use Consumer's Powerswitch website to check whether they could save money by switching electricity providers.
"Tens of thousands of people have switched, and that's carried through this year," she said.
"Eventually, prices will start to converge, but at the moment there are still plenty of reasons for people to check out their cheapest plan and provider."
But Ms Chetwin said increases were largely inescapable in the long term.
Chillingas powerbills bustbudgets> From Page 1A report by Consumer NZ last year said that since 2003, average power prices for homes had risen by almost 7% a year.
Between 1982 and 1992, the average increase was only 0.6% a year.
"Energy prices are becoming an increasing part of people's bills, to a worrying extent," Ms Chetwin said.
Powershop chief executive Ari Sargent said the increases were caused by network upgrades, more risk in the wholesale market, and lower hydro-electricity lake levels.
Most power companies increased prices after grid operator Transpower and local lines companies increased their charges.
Lines charges account for about 40% of customer bills.
Yesterday, State Owned Enterprises Minister Tony Ryall said Government moves to increase competition in the sector were working.
"New Zealanders are increasingly taking advantage of that [regulatory] change and are switching companies for a cheaper deal.
"Treasury advises that in the 12 months from May 2011 to April 2012, 422,256 customers changed electricity retailers."
Creation of the powerswitch.
org.nz website and a switching campaign last year prompted bigger retailers such as Contact Energy to introduce discounts to stem their loss of customers.
Ms Fox said many low-income families were using plans which charged the same monthly fee over the whole year - something she encouraged.
"You build up credit in summer to take care of the winter bills, because to suddenly be finding more money in the middle of winter is really hard."
