Pool heat pumps in NZ: what size you need and what it costs

Size a pool heat pump at 1 kW for every 1,000 litres of water, then add 20 to 30% (Pacific Pools' rule): about 24–26 kW for a 20,000-litre pool and 54–58 kW for a typical 8 m × 4 m pool. Tradie Tools NZ puts an installed pool heat pump at $3,000 to $6,000 and $800 to $2,500 a year to run (June 2026).

What size heat pump do I need for my pool?

Start with the pool's volume. Pacific Pools' rule is pool volume in litres ÷ 1,000 = minimum heat output in kW, and it recommends buying 20 to 30% above that minimum so the unit is not running flat out. A 20,000-litre pool needs at least 20 kW, so 24–26 kW. If you don't know the volume, our pool volume guide works it out from length, width and depth.

That rule is on the generous side. It is meant to heat a pool through a long season, from spring to autumn, in a typical New Zealand climate. Retailers often sell smaller units for the same pool, and a smaller unit will get there, just more slowly and with less in reserve on cold nights. Lean to the top of the range if the pool is uncovered, exposed to wind, in the south, or if you want to swim before Labour Weekend.

How much does a pool heat pump cost in NZ?

Published New Zealand figures run from $3,000 installed for a small unit to well past $15,000 for a large inverter unit with a hard installation. The two things that move the price are the size, which follows the pool's volume, and the type of compressor: a standard on/off unit costs least, and an inverter or full inverter unit costs more but uses less power.

Tradie Tools' $3,000–6,000 and Pacific Pools' unit prices are measuring different things: the first is a typical installed job, the second prices big units sized to its own generous rule, in Auckland, two years earlier. Only CheckMyBuilder says whether its figures include GST (they don't), so ask which you are being quoted.

Worked example: an 8 m × 4 m pool

An 8 m × 4 m pool averaging 1.4 m deep holds about 44,800 litres. On Pacific Pools' rule it needs at least 45 kW and should have 54–58 kW, which puts it in the 60 kW band. Adding Pacific Pools' installation range to its 60 kW unit prices gives these totals. This is our arithmetic from its April 2024 figures, not a quote.

The inverter premium is $2,000–3,000 on the unit. Pacific Pools gives standard units a coefficient of performance (COP, heat out per unit of power in) of 4–6, inverters 6–8 and full inverters 8–12. If a standard unit costs $1,600 a year in power, an inverter at the same output would use roughly a quarter to a third less, so the premium pays back over several seasons. That is our arithmetic from the COP ranges, and it only holds if you heat the pool every season.

How much does a pool heat pump cost to run?

Tradie Tools NZ puts a pool heat pump at $800 to $2,500 a year to run. Pacific Pools prices a 60,000-litre pool heated for eight months at $1,200–2,000 a season in electricity, plus $200–400 a year in maintenance, so $1,400–2,400 in all. What decides where you land is the set temperature, the length of the season, the region, and above all whether the pool is covered at night.

Does a pool heat pump work in winter in New Zealand?

It works, but it struggles. Pacific Pools says standard pool heat pumps operate down to 7–10°C air temperature. Below that they slow right down, which is a lot of a southern winter night. Most owners use a heat pump to stretch the season from spring to autumn. Holding a pool warm through a Queenstown July takes a big unit, a cover and a large power bill.

How long does a pool heat pump last?

Pacific Pools gives pool heat pumps a lifespan of 10 to 15 years. Coastal salt air, a unit jammed against a wall with no airflow, and a pool chemistry that eats the heat exchanger all shorten it, so site it with clear air around it and keep the water balanced. Our water testing guide covers the balance.

Can I install a pool heat pump myself?

Partly. Plumbing a heat pump into the pool's filter line after the filter is a straightforward pipe job. A unit this size usually needs its own circuit from the switchboard, though, and fixed wiring is a job for a registered electrician. Budget for both: the installation figures above include the plumbing, the electrical work and the pad the unit sits on.

Heat pump or solar?

A heat pump if you want the pool warm on a cloudy week or early in spring; solar if you have a big north-facing roof and mainly want to stretch summer, because it costs a fraction as much to run. Many pools use both. Our solar pool heating guide sizes and prices panels, and pool heating NZ compares all three heaters. Planning a new pool? The pool cost calculator shows what heating adds to the build.