How much does a heat pump cost to run in NZ?
A modern 2.5 kW heat pump running six hours a day costs about $46 a month in Christchurch at the May 2026 MBIE retail rate of 38.5 c/kWh. That's around $10 a week to heat a room properly through winter, roughly a third of what a plug-in oil column heater would cost to do the same job.
But the number depends on three things: the heat pump's , your local electricity rate, and how long you run it. Here's how to work out your own.
The formula
A "2.5 kW heat pump" means the unit delivers 2.5 kilowatts of heat into the room. The electricity it draws to do that is:
electricity drawn (kW) = heat output (kW) ÷ COP
is short for Coefficient of Performance, which is just a measure of how much heat you get out for each unit of electricity you put in. A good modern heat pump in Canterbury runs around COP 3.8 when it's 7°C outside. So:
- 2.5 kW of heat ÷ 3.8 = 0.66 kW of electricity drawn
- 6 hours a day × 0.66 kW = 3.95 kWh a day
- 3.95 kWh × 30.4 days × 38.5c/kWh = $46/month at the May 2026 Christchurch rate
In a colder winter month when COP drops to around 3.3, the same six hours costs closer to $53/month. Bear in mind the figure is a rate for a typical small household and may differ from your actual per-kWh rate, particularly if you are on a with a higher daily fixed charge.
COP depends on the weather
Heat pumps get less efficient the colder it gets - they have to work harder to pull warmth out of cold air. Typical COP ranges by region:
- Auckland / Northland: COP 4.0-4.5 most of winter
- Wellington / lower North Island: COP 3.7-4.0
- Christchurch / Canterbury: COP 3.6-3.9 (cold mornings drop it)
- Southland / Central Otago: COP 3.0-3.5 (frost country)
The COP printed on the unit sticker is usually the peak efficiency at a mild temperature. Real-world annual average COP is usually 0.3-0.5 lower.
Heat pump vs plug-in heater
The same 6 hours a day from a 2,400 W oil column heater: 2.4 kW × 6 h × 30.4 days × 38.5c = $169/month. That is $123 a month more than the heat pump for the same amount of heat in the room. Over a Canterbury winter (four months of heavy heating) that compounds to roughly $490 extra.
What it costs across the regions
Two things move between regions: the retail rate you pay per kWh, and the real-world winter COP your unit achieves (colder air means a lower COP). Putting both together for the same job - a 2.5 kW heat pump running 6 hours a day - gives a useful spread. The table below uses a region-appropriate winter COP and the May 2026 MBIE retail rate.
| Region | Rate (c/kWh) | Winter COP | Per month |
|---|---|---|---|
| Auckland Central | 41.2 | 4.2 | ~$45 |
| Wellington City | 37.0 | 3.9 | ~$43 |
| Christchurch | 38.5 | 3.7 | ~$47 |
| Invercargill | 38.8 | 3.3 | ~$54 |
| Balclutha | 52.5 | 3.2 | ~$75 |
The Balclutha number is double the Auckland one, and that is for the same heat pump doing the same job. About a third of the gap is the higher rate, and the rest is the colder air dragging the COP down. It is a reminder that running cost is as much about where you live as it is about the unit on the wall. If you want the figure for your own town, the heat pump cost page lets you set the rate and COP directly.
Common things that inflate the number
Most people who think their heat pump is "expensive to run" are losing money to one of a handful of avoidable habits rather than to the unit itself:
- Setting the thermostat too high. Every degree above 20C adds roughly 10% to the daily running cost, and 24C does not heat the room any faster - it just keeps the compressor working past the temperature you actually wanted. See the heat pump temperature guide.
- Dirty filters. A clogged filter chokes airflow and can knock 10-25% off the effective COP. Vacuum them monthly through winter - it is a five-minute job that pays for itself.
- Running it in a leaky room. If the heat falls out of the building faster than the unit can replace it, the compressor never throttles back and you pay full whack all day. Draughts and an uninsulated ceiling are usually the culprits - more on that in insulation vs heat pump.
- Heating empty rooms. A multi-split left on across the whole house warms bedrooms nobody is in. Heat the room you are sitting in, not the floor plan.
- An oversized unit. A heat pump that is too big short-cycles - on, off, on, off - which runs it at a lower real-world COP than a right-sized unit cruising steadily.
Worth checking: your daily fixed charge
The per-kWh figures above are only half the bill. Every connection also carries a daily fixed charge, typically $1.50-$3.00 a day depending on your region and whether you are on a standard or low-user tariff. That is $45-$90 a month before you switch a single appliance on. It does not change how much your heat pump costs to run, but it does mean that if your goal is a lower total bill, comparing retailers and tariff types can matter as much as how you heat. The average power bill guide breaks the fixed portion down by region.
Work out your own number
The NZ Power Bill Calculator does this calculation live - tick the heat pump, set its heat output and COP, and it'll show you your monthly cost and the plug-in heater comparison for your region.
Related guides
- What temperature to set your heat pump in NZ winter - how thermostat setting affects running cost
- Insulation or a heat pump: where to spend first - why the building shell matters more than the heater
- Heat pump vs wood burner: which is cheaper in NZ? - cost-per-kWh comparison
- The most expensive appliances in NZ homes - where heating sits against everything else
- Average NZ power bill by region (2026) - put the heat pump figure in context