Consumer survey reveals best way to heat house and save on power without breaking bank this winter.

If you worry about the power your mobile phone uses when you leave it charging all night, relax. A new Consumer survey has found that it costs less than a cent a week.

But if you run a large, hot, soothing bath, it will cost you $1.54 a time, almost double the 83c cost of a 10-minute shower.

And if you run a two-bar heater for five hours in the evening, it will cost almost $3, or more than $20 a week.

"Generally 30 to 35 per cent of your power bill is space heating," says Auckland Council eco design adviser Adrian Feasey. "So if your home is not insulated, the first thing to look at is to have good insulation so that any heating is retained better."

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The Consumer survey finds the power costs of heat pumps are comparable with traditional heaters - 30c an hour at a heat pump's minimum output up to 43c at maximum, compared with 29c an hour for a one-bar electric heater or a small oil-filled heater or 58c an hour for a two-bar electric one or a large oil-filled one.

It depends on the situation. A heat pump typically is better for a larger room, whereas for a smaller room like a bedroom where you are looking to reach 18C which the World Health Organisation recommends, the best solution is a column [oil or oil-free] heater on a thermostat or a timer.

Another 30 per cent of the typical home power bill goes on hot water, chiefly for showers and baths.

Olivia Tukuogo, who runs a Watercare-funded water advice line at the EcoMatters Environment Trust for Auckland households, says the two best ways to save water are to have shorter showers and to fit a $10 flow restrictor over the shower head.

"That saves on both power and water," she says.

Fridges and freezers use about 11 per cent of a typical home's power bill. Consumer says a new energy-efficient fridge/freezer will cost you only 32c a day against 51c a day for a 15-year-old model.

Energywise efficient products manager Eddie Thompson says modern products are labelled. "If you're in the market for a new appliance, look for the energy rating label," he says. "The more stars, the better."

Lighting typically accounts for 8 per cent of the power bill. Consumer says energy-efficient 100-watt-equivalent compact fluorescent light bulbs cost only 3c for six hours, saving 80 per cent of the 15c cost of traditional 100-watt bulbs.

The average home uses a further 6 per cent of its power for cooking, 4 per cent for other appliances and 12 per cent for televisions, computers, other electronic devices and everything else.

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Auckland Council provides free eco design advice.

Mother's vigilance takes the heat out of power bills

Olivia Tukuogo reckons she saves money by giving her children baths, even though in theory a shower is cheaper.

Mrs Tukuogo says that's because her daughters, aged 7 and 9, share the bath which is only about a third full. Two-year-old son Quade has his own tub in the shower cubicle.

The five adults in the house - Mrs Tukuogo and husband Talesi Tukuogo, Mr Tukuogo's two sons in their early 20s and one son's partner - typically have five-minute showers. The family's latest monthly power bill was $196.

"We are pretty good on power, we couldn't do much more to save except retaining the heat," says Mrs Tukuogo, who operates a Watercare-funded water advice line for Auckland consumers through the EcoMatters Environment Trust.

After shivering through their first winter in their West Harbour house six years ago, Mrs Tukuogo called in an Auckland Council eco design adviser to suggest ways to save power. They topped up the insulation in the ceiling, installed it under the floor, wrapped the hot water cylinder and later wrapped insulating lagging around their hot water pipes under the house.

They use two fan heaters and an oil column heater sparingly, have an energy-efficient fridge-freezer that is less than 10 years old, and have replaced about half the light bulbs with energy-efficient compact fluorescent bulbs.

"I'm the instigator of our power saving," Mrs Tukuogo says. "We don't leave anything on standby and I'm pretty conscious of hot water use." But some windows still need curtains. "That's my next project."