Consumer Watch: Heat pump misuse goes on bill

For the first few months after a new heat pump is installed, households tend to get very high power bills, studies show. Photo / Thinkstock

Households are not making the most of the heating system and may pay too much.

You have a heat pump, so your power bill should be cheaper this winter, right? Not necessarily.

Heat pumps are the most commonly installed form of fixed heating. But experts say many people are paying unnecessarily high bills because they aren't using them correctly.

Mikael Boulic, a lecturer at the Massey University school of engineering and advanced technology, and part of the Housing and Health Research Programme, said more education was needed to help New Zealand households use their heat pumps more effectively.

His studies have shown that for the first couple of months after a new heat pump is installed, households tend to get very high power bills.

Boulic said this was because residents would come home to a cold house and crank up the heat pump to its highest setting.

"They would set it for 29°C or 30°C, so the heat pump is running at a very high rate for a few minutes.

"It then gets too hot so they shut it down instead of leaving the temperature at 18°C and waiting for it to reach that," he said.

People with a new system also tended to heat their houses to much warmer temperatures, so their power bills increase.

Another mistake was leaving the heat pump on all day when no one was home, the Energy Efficiency and Conservation Authority said. If it was set to 20°C, the heat pump could start using more power, wasting money on an empty room.

When operated correctly, heat pumps top the list as the most fuel-efficient device. Standard electric heaters convert 100 per cent of the power they use into heat, but heat pumps generate $2.50-$5 worth of heat for every $1 of power.

A 4kW plug-in heater will cost about $1 an hour to use. But a heat pump that consumes that same amount of power would give consumers two or three times the heat for the same price.

Using a heat pump for a few hours in the evening and an hour in the morning could generate savings of about $500 a year.

Size is an issue, too. To get the best out of a heat pump, Consumer New Zealand technical writer George Block said it should be chosen specifically for the room or rooms be heated. A heat pump that is too small will have to work harder and use more power.

Heat pumps have reliability on their side, however.

Ninety-two per cent of responders to a recent Consumer NZ survey said their heat pumps aged up to five years had not needed any repairs.

Heat pumps range from $1,100 to more than $10,000 for a whole-house system, and installation costs $750-$1350.

As New Zealanders brace for the June 1 official start to winter, home owners who can't afford a heat pump, and tenants whose landlord won't install one, should take note of the findings of Consumer NZ's latest electric heater tests. It found that convector or oscillating tower heaters were best for living areas in well-insulated houses.

Heaters with fans were best in living areas, Block said, because they distributed heat evenly.

Oil column and panel heaters were best for bedrooms, because they only needed the chill taken off overnight and a panel or oil heater was a cheaper way to do that.

Those living in uninsulated or draughty houses would be best-served with an oscillating tower heater or a micathermic one, cased in mica sheets that transmit heat.