Heat pump or plug-in heater: what's cheaper to run in NZ?

Quick answer: A heat pump. EECA says heat pumps cost about a quarter as much to run as bar and column heaters, because the average heat pump in New Zealand puts out around three times more heat than the power it uses. A plug-in heater turns every unit of power into one unit of heat, no more. Heat pumps cost more up front (EECA puts it at around $4,400 installed), so plug-in heaters still make sense for small rooms you only heat now and then.

Why is a heat pump so much cheaper to run?

A plug-in heater, whether it's a fan, oil column, panel or bar heater, converts electricity straight into heat. EECA describes them as all being 100% efficient, which sounds good until you compare it with a heat pump.

A heat pump doesn't make heat from the power. It moves heat from outside into the room, using the power to run the pump. EECA says the average heat pump here puts out three times more heat than the power it uses, and that, set against bar and column heaters, heat pumps are about a quarter of the cost to run.

That gap matters because heating is a big part of the bill. EECA estimates heating makes up about a third of the energy bill in the average Kiwi home.

What does a plug-in heater actually cost to run?

EECA's figures, at an electricity price of 35 cents a kWh:

• a 250W heater: about 9 cents an hour
• a 1000W heater: about 35 cents an hour
• a 2400W heater on full: about 84 cents an hour

Most portable heaters are 2000W or 2400W. A thermostat helps, cutting energy use by around 9% on EECA's numbers, so if you do use a plug-in heater, get one with a thermostat.

When does a plug-in heater still make sense?

EECA's view is that plug-in heaters are a good option for bedrooms, studies and other small rooms. They're cheap to buy, you can move them around, and if you only heat a room for an hour or two, the running cost difference doesn't add up to much.

For the room you heat most, usually the living room, a heat pump is where the savings are. EECA calls heat pumps the lowest-cost and lowest-emission option for living areas and anywhere that needs frequent heating or cooling.

What does a heat pump cost up front?

EECA puts a typical heat pump at around $4,400 including installation, with a lifespan of about 15 years. It has to be installed by a licensed electrician.

There are three main types:

• Single-split: one outdoor unit and one indoor unit, heating one room. Easiest and cheapest to install.
• Multi-split: one outdoor unit running several indoor units, for larger homes.
• Ducted: central heating through ducts to several rooms. Usually the most expensive up front.

Most heat pumps can cool as well as heat, which EECA lists as one of their features.

How do you buy the right one?

Size matters. EECA's advice is that too small and it will struggle, too big and you'll pay more than you need to. A good supplier should come to your place and look at the size of the room, the windows and your climate before recommending one.

Efficiency varies between models too. EECA's efficient appliance calculator lets you compare heat pumps sold in New Zealand by their energy rating.

Placement makes a difference. EECA suggests putting the indoor unit high on an exterior wall, away from corners, with the outdoor unit within around 15 metres of it and clear space around it for airflow.

On Cogo, heating is one of the most common upgrades people ask installers about: about one in five upgrade requests is for better heating.

How do you keep the running cost down?

EECA's tips for using a heat pump well:

• set it between 18 and 21 degrees, warm enough to fight damp and mould without wasting power
• don't run it 24/7; EECA calls that a myth, and it uses more energy overall
• use the timer so the room is warm just before you get home or get up
• clean the filter about once a month over winter
• leave the fan on auto

Insulation and draught-stopping make every heater work less hard. And it's worth checking your power plan: time-of-use plans with cheaper off-peak power can suit households with electric heating. The Electricity Authority's free comparison service, Billy, can help.

If you're moving off gas, EECA estimates a heat pump costs an average household $122 a year less to run than piped gas heating, and $352 a year less than bottled LPG, before you count the daily connection or bottle charges. We've written about what going all-electric is worth on a power bill.

FAQ

Is a heat pump cheaper to run than an electric heater?

Yes. EECA says heat pumps cost about a quarter as much to run as bar and column heaters, because they put out around three times more heat than the power they use.

How much does a 2400W heater cost to run per hour in NZ?

About 84 cents an hour on full, at an electricity price of 35 cents a kWh, on EECA's figures.

What temperature should I set my heat pump to?

EECA recommends between 18 and 21 degrees.

Should I leave my heat pump on all the time?

No. EECA says running it 24/7 uses more energy overall. Use the timer instead.

See what a heat pump would save you

Every house is different. Run your own numbers with Cogo to see what better heating could save your household, and ask installers for quotes from there.

This article is general information only. It is not financial, energy or product advice. What you save depends on your home, your power plan and how you use energy, so get quotes from qualified installers or licensed dealers and seek independent advice for your own situation.