Typical heat pump running cost in NZ
These are real outputs from the estimator on this page, with a cover, outdoors, a concrete pool 1.25 m deep on average, a target of 28 C, 8 hours a day and power at 35 cents a kWh. The 30,000 litre pool is 6 m by 4 m, the 45,000 litre pool is 9 m by 4 m and the 60,000 litre pool is 9.6 m by 5 m.
Season cost is electricity only. The heat pump is the smallest AquaTherm or AquaTherm PRO whose pool volume rating covers the pool. On these pools the heat pump runs about 13 to 22 hours a day in the coldest month of a summer and 17 to 26 hours a day over November to March. Over 24 hours means one unit cannot quite keep up in that month, as in Christchurch at 45,000 litres, and the estimator says so. The cost is the energy used either way.
What drives the cost of heating a pool
Seven things move the bill. The first two matter most.
- Pool cover. The biggest single factor, shown in the next section. Most of a pool's heat leaves through the surface.
- Target temperature. Every extra couple of degrees costs a lot more than the last. Tauranga, 30,000 L, with a cover, extended seasonSeason costTarget 26 C$470Target 28 C$791Target 30 C$1,145
- Your town. A colder town needs more heat. For the same 30,000 litre pool and the extended season, Auckland is $711, Tauranga $791 and Christchurch $993.
- Season length. Heating only December to February costs $433 in Tauranga against $791 for November to March. Heating through winter in a cooler town needs a bigger unit and is best talked through with Gina.
- Power price. The cost moves in step with your price per kWh. Same pool, power price per kWhSeason cost30 cents$67835 cents$79140 cents$904
- Wind. A pool in the open loses more heat than one that is sheltered. The estimator treats an indoor pool as sheltered from the wind, and the Tauranga pool drops from $791 to $572.
- Pool material. Concrete and tiled pools lose more heat than fibreglass or a liner in the estimator. The same Tauranga pool costs $791 in concrete, $598 in fibreglass and $501 with a plastic liner.
All of these are the same Tauranga pool, 6 m by 4 m and 1.25 m deep with a cover and the extended season, changing one thing at a time. The heat pump is the same in each case.
Pool cover or no cover: the big one
A heat pump heats the water in the day. Without a cover the water gives that heat back to the night air, so the pool needs more than twice the heat. Here is the same 20,000 litre pool, 5 m by 3.2 m and 1.25 m deep, with the cover on and off, on the same heat pump.
A bigger pool shows the same pattern. The 30,000 litre Tauranga pool costs $433 over a summer with a cover and $981 without one.
How a heat pump works, and what COP means
A heat pump does not make heat from electricity the way an element does. It pulls heat out of the outside air and moves it into your pool water, a bit like a fridge working in reverse. Moving heat takes far less power than making it.
COP is the coefficient of performance: heat delivered divided by electricity used. Davey's figures for the AquaTherm range come to about 5 to 7 at 15 C air. One unit of power moves five to seven units of heat. An element heater is 1. COP drops on cold nights, which is why a cooler town and a longer season cost more to heat.
Ways to cut the cost of heating your pool
- Use a cover every night. It is the cheapest cut by a long way. See the table above.
- Lower the target a little. Dropping from 28 C to 26 C in the Tauranga example takes the season from $791 to $470, about 41 per cent less.
- Heat for a shorter season. Add months only if you will use the pool in them.
- Shelter the pool from the wind. A fence or a hedge on the windy side helps.
- Run the heat pump in the warmest part of the day. A heat pump works better in warm air. Ring your power company about daytime rates.
- Get the size right. An undersized unit runs flat out and still does not get the pool warm. Use the pool sizing guide to check your litres.
Pool heating cost questions
How much does it cost to heat a pool in NZ?
For a 30,000 to 45,000 litre outdoor pool with a cover, heated to 28 C, the Pump Stuff estimator gives about $370 to $770 for a summer (December to February) and about $710 to $1,390 for an extended season (November to March), at 35 cents a kWh in Auckland, Tauranga and Christchurch. Without a cover the cost more than doubles.
How much does it cost to run a pool heat pump per day?
About $5 to $7 a day on average in the estimator's Tauranga examples. A 30,000 litre pool with a cover costs $433 over a summer of 90 days and $791 over a November to March season of 151 days. A 45,000 litre pool costs $608 and $1,110. Cooler nights and a higher target push the daily figure up.
Do I need a pool cover with a heat pump?
Yes. A pool loses most of its heat from the surface, overnight and in the wind. In the estimator's 20,000 litre examples, leaving the cover off multiplies the running cost by 2.1 to 2.4, and the heat pump has to run flat out to keep up.
What temperature should I heat my pool to?
Most families are happy at 26 to 28 C. Each two degrees makes a big difference to the bill. In the Tauranga example a 30,000 litre pool costs $470 a season at 26 C, $791 at 28 C and $1,145 at 30 C.
What is COP on a heat pump?
COP is the coefficient of performance: units of heat delivered for each unit of electricity used. Davey's published figures for the AquaTherm range are about 5 to 7 at 15 C air, so 1 kWh of power moves 5 to 7 kWh of heat into the water. An electric element heater has a COP of 1. COP falls on cold nights.
Is a heat pump cheaper to run than an electric element heater?
Yes, by a long way. An element turns 1 kWh of power into 1 kWh of heat. At a COP of 5 to 7 a heat pump delivers the same heat for roughly one fifth to one seventh of the electricity.
How accurate is the heat pump running cost estimate?
It is a guide, not a quote. It uses Davey's pool heat loss method with Davey's published efficiency at 15 C air, so it errs on the realistic side. Your real cost depends on your pool, how you use the cover, the weather and your power price. For an assessment for your address, ring Gina on 027 322 4200.
Do I need an electrician to install a pool heat pump?
The electrical connection needs a licensed electrician. The plumbing can be done by you, a pool installer or a plumber. Ring 07 863 8064 and a real person will help.
What size heat pump does my pool need?
Pick the smallest AquaTherm or AquaTherm PRO whose pool volume rating is at or above your litres, and use a cover. The estimator on this page does that for you, and the pool sizing guide shows how to work out your litres.
