Illustration.
The three options
| Solar | Heat pump | Gas | |
|---|---|---|---|
| How it heats | Pool water is pumped through collectors on the roof | Extracts heat from the air with a compressor, like a reverse-cycle air conditioner | Burns natural gas or LPG |
| Running cost | Lowest: only the pump | Electricity; several units of heat for each unit of power | Highest per hour of heating |
| Works when | Sunny days; less in winter | Most weather, slower when the air is cold | Any time, heats fastest |
| Installation | Roof collectors and plumbing | An outdoor unit, plumbing and usually its own electrical circuit | A gas line and flue |
Start with a cover
Most of a pool's heat is lost from the surface. HealthyWA notes an uncovered 8 by 4 metre pool can lose around 15 mm of water a day to evaporation, and evaporation carries heat with it. A cover on a heated pool cuts both, so it is the first thing to buy whichever heater you choose.
Who installs them
Heat pumps usually need their own electrical circuit, which must be installed by a licensed electrician, and plumbing by a pool technician or plumber. Gas heaters must be connected by a licensed gas fitter. Solar collectors go on the roof with plumbing to the pool equipment.
Running cost drivers
How warm you want the water, how many months you heat it, whether you use a cover, your local climate, and your electricity or gas price. The SA Government notes a pool typically uses 2,000 to 3,000 kWh of electricity a year before heating, depending on the pump and how long it runs.
Heat pumps work best on the warmest part of the day. If you have solar panels, set the heat pump to run when they are producing.
Common questions
What is the cheapest way to heat a pool?
Solar is cheapest to run, because the sun does the heating and you only pay to pump the water. A cover makes any heater cheaper.
How much does it cost to heat a pool with a heat pump?
It depends on the size of the pool, the temperature you want, the season and your electricity price. Heat pumps move several units of heat for each unit of electricity, which is why they cost less to run than gas.
Does a heat pump need an electrician?
Usually, yes: a dedicated circuit must be installed by a licensed electrician.