Air Source Heat Pump Swimming Pool Heating
If you have a swimming pool — or you are planning to install one — heating it efficiently is one of the biggest ongoing costs you will face. An unheated outdoor pool in the UK is usable for perhaps three months of the year. A heated pool extends that to six months or more, and an indoor pool needs year-round heating.
Air source heat pumps are by far the most efficient way to heat a pool. They cost a fraction of what gas or electric resistance heaters use in energy, and they have become the standard choice for pool heating across the UK and Europe.
This guide covers everything you need to know: dedicated pool heat pumps vs using your home heat pump, sizing, costs, running costs, and practical installation considerations.
How Does a Pool Heat Pump Work?
A pool heat pump works on exactly the same principle as a home heating heat pump — it extracts heat from the outside air and transfers it to water. The difference is that instead of heating water for radiators, it heats pool water directly.
Pool water is pumped from the pool, through the heat pump's heat exchanger, and back to the pool in a continuous loop. The heat pump raises the water temperature by a few degrees each pass. Over several hours, the entire pool reaches the target temperature — typically 26-30°C for comfortable swimming.
For a detailed explanation of the underlying technology, read our guide on air source heat pumps.
Dedicated Pool Heat Pump vs Home ASHP
There are two approaches to heating a pool with a heat pump, and the right choice depends on your situation.
Dedicated Pool Heat Pump
A dedicated pool heat pump is a standalone unit designed specifically for pool heating. It sits beside the pool, connects to the pool's filtration circuit, and does nothing else. It is completely separate from your home heating system.
Advantages:
- Purpose-designed for pool water chemistry (titanium or treated heat exchangers resist chlorine corrosion)
- Simple installation — connects to existing pool plumbing
- Does not affect your home heating capacity
- Can be sized specifically for the pool
- Cheaper units available since they do not need to meet MCS standards
Disadvantages:
- An additional unit to buy and maintain
- Takes up space beside the pool
- Not eligible for the BUS grant (pool heating does not qualify)
Using Your Home ASHP for Pool Heating
Some home air-to-water heat pumps can be configured to heat a pool as well as the house. This requires a secondary heating circuit with a pool heat exchanger — the heat pump heats a separate water loop that passes through a heat exchanger in the pool circuit, transferring heat to the pool water without the two water bodies mixing.
Advantages:
- One system for everything — no separate pool heat pump to buy
- Can be more efficient if the home heat pump is already oversized for the house
Disadvantages:
- Reduces capacity available for home heating — can be a problem in winter if the heat pump is trying to do both
- More complex installation with additional plumbing and controls
- Pool heating demand may conflict with the BUS grant eligibility (the heat pump must be primarily for home heating)
- Pool water chemistry must be kept separate — requires a plate heat exchanger, adding cost
- Warranty implications — check with the manufacturer
For most pool owners, a dedicated pool heat pump is the simpler and more practical choice. Using your home ASHP for pool heating is only worth considering if you have a significantly oversized home heat pump with spare capacity.
How to Size a Pool Heat Pump
Pool heat pump sizing depends on several factors:
Pool Volume
The starting point is the volume of water to be heated. Calculate this as length x width x average depth. A typical domestic pool of 8m x 4m x 1.4m average depth holds about 45,000 litres (45 cubic metres).
Temperature Rise Needed
In the UK, unheated pool water sits at roughly 10-15°C in spring and autumn, and 15-20°C in summer. If you want to swim at 28°C, you need a temperature rise of 8-18°C depending on the season.
Heat Loss
An outdoor pool loses heat through evaporation (the biggest factor — up to 70% of heat loss), radiation, convection, and conduction through the pool walls. A pool cover dramatically reduces evaporation losses and is the single most effective thing you can do to reduce heating costs.
Sizing Guidelines
As a rough guide:
- Small pool (up to 30m3): 8-12kW heat pump
- Medium pool (30-50m3): 12-18kW heat pump
- Large pool (50-80m3): 18-25kW heat pump
- Indoor pool: typically needs a smaller unit as heat losses are lower
These are guidelines for outdoor pools with a cover used when not swimming. Without a cover, you may need a unit 30-50% larger. A pool heating specialist can do a precise calculation based on your specific pool, location, and usage pattern.
Pool Heat Pump Costs
Unit Costs
- Budget pool heat pumps (8-12kW): £1,200-£2,000
- Mid-range pool heat pumps (12-18kW): £2,000-£3,500
- Premium pool heat pumps (18-25kW): £3,500-£5,500
Installation Costs
Pool heat pump installation is relatively simple if you already have a pool with a filtration system. The heat pump connects into the filtration loop after the filter and before the return to the pool. Typical installation costs are £300-£800, depending on the complexity of the plumbing and electrical connection.
Total Installed Cost
For a typical domestic outdoor pool, expect to pay £2,000-£4,500 total for a dedicated pool heat pump fully installed. This is a fraction of what a gas pool heater costs to run over its lifetime.
Running Costs: Heat Pump vs Gas vs Electric
This is where pool heat pumps really shine. The efficiency advantage over other heating methods is enormous.
Comparative Annual Running Costs (45m3 Outdoor Pool, Heated April-September)
- Air source heat pump (COP 5.0): £400-£700 per year
- Gas pool heater: £1,500-£2,500 per year
- Electric resistance heater: £3,000-£5,000 per year
Pool heat pumps achieve higher COPs than home heating heat pumps because they operate during warmer months (April-September) when outside temperatures are higher, and pool water only needs to be heated to 26-30°C — a much smaller temperature lift than home heating requires in winter.
A pool cover is essential for keeping running costs down. Using a cover when the pool is not in use can reduce heating costs by 50-70%.
Can You Heat a Pool Year-Round?
Yes, but it gets expensive. An outdoor pool in the UK loses heat rapidly in winter, and the heat pump's efficiency drops as outside temperatures fall. Heating an outdoor pool through winter is technically possible but economically questionable — you might spend £200-£400 per month in electricity during the coldest months.
Indoor pools are a different story. With lower heat losses (no wind, no evaporation to open air), an indoor pool can be heated year-round at reasonable cost — typically £50-£120 per month depending on size and insulation.
If you want year-round outdoor swimming, a pool enclosure or retractable cover is a better investment than a larger heat pump — it dramatically reduces heat loss and extends the swimming season with much lower ongoing energy costs.
Installation Considerations
Positioning
Place the pool heat pump as close to the pool plant room or filtration equipment as practical. Longer pipe runs mean more heat loss and more pumping energy. The unit needs good airflow — at least 300mm clearance on all sides, and it should not be enclosed in a tight space.
Noise
Pool heat pumps run their fans at higher speeds than home heating units because they are working harder (heating large volumes of water). Noise levels are typically 45-55 dB at one metre. Position the unit away from neighbours' boundaries and away from outdoor seating areas if noise is a concern.
Electrical Supply
Most domestic pool heat pumps run on a single-phase electrical supply. Larger units (above 18kW) may require a three-phase supply, which not all domestic properties have. Check this before purchasing.
Pool Cover
We cannot stress this enough: a pool cover is not optional if you want reasonable running costs. A good thermal cover costs £500-£2,000 depending on the pool size and type (manual bubble cover vs automatic slatted cover). It pays for itself within one season through reduced heating costs.
Brands and Models for Pool Heating
The main pool heat pump brands available in the UK include:
- Hayward — one of the most established pool equipment brands, wide range of heat pumps
- Zodiac — premium pool heat pumps with high efficiency ratings
- Fairland — good value mid-range options, increasingly popular in the UK
- BWT — German-engineered, strong reputation for reliability
- Hot Splash — budget-friendly option suitable for smaller pools
- Daikin / Mitsubishi — available for pool heating via home ASHP integration (not dedicated pool units)
Pool Heat Pumps and Planning Permission
A dedicated pool heat pump is generally treated the same as a home air source heat pump for planning purposes — permitted development in most cases, provided noise limits and boundary distances are respected. In conservation areas or for listed buildings, you may need planning permission.
The unit must comply with noise regulations. Since pool heat pumps tend to run during the day (when you are swimming or preparing to swim), noise is less likely to be an issue than a home heat pump running early in the morning.
Frequently Asked Questions
Can my home heat pump heat my swimming pool?
Some home air-to-water heat pumps can be configured to heat a pool via a secondary circuit and plate heat exchanger. However, this reduces the capacity available for home heating and adds complexity. For most pool owners, a separate dedicated pool heat pump is simpler and more practical.
How long does a pool heat pump take to heat the pool?
From cold (10-15°C) to swimming temperature (28°C), a correctly sized pool heat pump typically takes 24-72 hours for an average domestic pool. Once at temperature, maintaining it requires much less energy — especially with a pool cover.
Is a pool heat pump eligible for the BUS grant?
No. The Boiler Upgrade Scheme grant is for home heating systems only. Dedicated pool heat pumps do not qualify. If your home ASHP also heats the pool, the grant applies to the home heating function only — the pool heating element does not affect eligibility, provided the primary purpose is home heating.
How much does it cost to heat a pool per month?
With an air source heat pump and a pool cover, expect to pay £60-£120 per month during the swimming season (April-September) for a typical domestic outdoor pool. Without a cover, costs can double or triple.
Do pool heat pumps work in cold weather?
Yes, but their efficiency drops as outside temperatures fall. Most pool heat pumps work down to 5-10°C ambient temperature. Some models rated for lower temperatures can operate down to -5°C or below, but running costs increase significantly. For winter pool heating, ensure you choose a model rated for low ambient temperatures.
How long does a pool heat pump last?
A quality pool heat pump typically lasts 10-15 years with proper maintenance. The main vulnerability is the heat exchanger, which must resist corrosion from chlorinated pool water. Titanium heat exchangers last longest. Ensure the water chemistry is properly maintained to maximise the heat pump's lifespan.