Where your pool's electricity goes and how to cut it
In a pool without heating, most of the electricity is used by the circulation pump. If there is a heat pump, that usually comes first. Both can be reduced noticeably with the right equipment and habits.
How consumption is calculated
The energy a device uses is its power multiplied by its running hours. A one-kilowatt pump running for eight hours uses about eight kilowatt-hours a day. That is why a device of moderate power that runs for many hours, like the pump, can use more than a powerful one that only switches on briefly.
The rated power is written on each device's nameplate, but the actual draw varies with the pipework, the filter and the speed. If you want to know exactly what your own pool uses, ask your electrician to fit an energy meter on the pool circuit, or note the readings on the house meter before and after one day with the pump running and one day without it.
What uses what
| Device | How long it runs | Share of consumption |
|---|---|---|
| Circulation pump | Many hours every day, all season | Large, the most constant consumer |
| Heat pump | While heating, mainly in spring and autumn | Large, while it runs |
| Counter-current swim system | Only while you swim | High power, few hours |
| Salt chlorinator, UV, dosing pumps | Together with the pump | Small |
| LED lighting | A few hours in the evening | Small |
| Robotic pool cleaner | A few hours, a few times a week | Small |
The pump: the most constant consumer
- Variable speed. The power a pump draws falls much faster than its speed: at half speed it needs about one eighth of the power. So more hours at low speed use less energy overall. More on this under variable-speed pumps.
- The right hours. Set the timer according to the season, not at the maximum all year round. See how many hours the pump should run.
- A clean filter. When the filter clogs, the pump works against greater resistance and moves less water. Backwash as soon as the pressure rises and empty the baskets regularly.
- Good design. A pump sized to the pool, short pipe runs and adequate pipe diameter. These are decided at the start, before the pool is built.
Heating: lower losses, less energy
Most of a pool's heat is lost through the surface, mainly through evaporation. That is why the most effective measure is a cover at night and whenever the pool is not in use. Also:
- Set a sensible temperature; every extra degree takes more energy.
- Let the heat pump run during the warm hours of the day, when the air is warmer and it works more efficiently.
- Shelter the pool from the wind, which speeds up evaporation.
- If you only want to stretch the season a little, solar heating can cover part of the need.
Small habits that add up
Switch off the pool lights when they are not needed, programme the robot instead of leaving it in all day, and check the timer after every power cut. If the house has solar PV panels, the pump hours can be scheduled for when they are generating. And do not switch off the pump to save electricity: green water needs far more hours of filtration and far more chemicals to recover.
Questions
Which uses more, the pump or the heating?
Without heating, the circulation pump. With a heat pump, the heat pump usually uses more while it is heating, especially in early spring and late autumn, when the air is cool and the water needs to rise by many degrees.
Can a variable-speed pump be fitted to an existing pool?
Usually yes, in place of the old pump. It needs checking that it matches the filter, the pipework and any heating or salt chlorinator that needs a minimum flow to operate.
See also
Variable-speed pump
Variable-speed pool pumps: why lower speed for more hours means less energy use and less noise, and how to…
Pump running hours
How many hours your pool pump needs to run: the turnover cycle, setting the timer by season, which hours of…
Heat pump
Pool heat pumps: how they take heat from the air, what COP means, how to choose the size, where the unit goes…