Do Solar Pool Covers Heat the Water? What a Solar Cover Really Does

The short answer

A solar pool cover is mostly an insulator, not a heater. Its main effect is to stop heat escaping from the water surface, and the saving you can count on is the heat you do not have to buy back. The US EPA describes solar (bubble) covers as designed to use the sun's energy to heat the pool, and measures their effectiveness as an evaporation cut of 50% to 95%, depending on shape and coverage. We found no independent UK measurement of how much heat the film itself adds, and the UK trade body SPATA's cover factsheet gives no solar-gain figure, so we do not quote one.

Why the cover matters more than the sun on it

Evaporation is the biggest way a pool loses heat. SPATA says an uncovered outdoor pool may lose as much as 90% of its heat through evaporation, and that a heat-retaining cover can save as much as 80% of the heat lost from the surface. The US EPA's WaterSense guide says solid covers can cut evaporation by more than 90% when in use and, for heated pools, save between 50% and 70% of heating costs; US Department of Energy guidance gives the same 50% to 70%. Each kilogram of water that evaporates takes about 0.68kWh of heat with it, so keeping the water on the pool rather than in the air is worth real energy.

What it saves on a real-sized pool

Our worked 8×4m example assumes a bubble cover used overnight and on non-swimming days removes 40% of the total heat demand, a cautious figure beside the 50% to 70% savings in the US guidance. Applied to the three most common ways of heating a pool:

Two things follow. The saving is largest where heat is dearest, so a cover repays itself fastest on direct electric heating and slowest on a heat pump. And the saving does not depend on whether the cover is a bubble type, as long as it stays on the water: the figures come from the demand cut, not from the film.

Solar cover or solar panels: which saves more?

They do different jobs, so the useful question is the order. A cover reduces how much heat the pool needs; panels (through a heat pump) or collectors supply what is left. On the worked pool the cover removes about 4,400kWh of heat demand a season, which cuts the electricity a heat pump needs, and the array that matches it, by about 40%. A 3.6kWp array costs about £5,700 at the DESNZ median of £1,595 per kW and makes about 3,500kWh a year, about 2,000kWh of it between May and September. Spend on the cover first, then size the panels to what is left: the worked running-cost example shows the sequence with every step priced.

Using a cover so it actually works

• On whenever the pool is not in use. A cover only works while it is on the water. The EPA quotes a 2016 US study in which only 15% of pool owners had a cover and used it regularly; we found no UK figure.
• A solar cover is not a safety cover. The EPA table marks solar (bubble) covers as unable to serve as a safety cover; check what any cover is certified for before relying on it.
• Make it easy to deploy. The EPA says automatic covers, a motor-driven reel or a hand-crank reel make regular use more likely. A cover left on the lawn saves nothing.
• Indoors the benefit shifts. SPATA says a good heat-retaining cover reduces humidity and almost completely stops condensation in an indoor pool, which lowers the load on the hall's ventilation.

What a solar cover costs

Prices vary widely with thickness and size. One Amazon UK listing we saw on 30 October 2026 offered a 126-micron rectangular solar blanket for an 8×4m pool at £52.99 (a retailer price, not an average, and a thin film). Our worked example assumes £300 for a thicker cover with a reel, and £300–£700 as a planning range; get quotes for your pool, because the payback above holds across that whole range on gas and direct electric heating. The wider efficiency sequence, including cover types and the pump, is on the covers and efficiency page.

Do solar water heaters really work?

Solar thermal collectors do heat pool water, and unglazed polymer collectors are the type typically used for pools, according to the US Department of Energy's consumer guide. They need a collector area that SPATA puts at usually over half the pool surface, and in the UK climate SPATA says it is not always easy to hold the temperature you want. The solar pool heating guide covers what they deliver, the downsides and the cost; the contact form below reaches us if you want your own pool worked.

Sources and assumptions

Figures were checked on 30 October 2026. Where we found no UK source we say so, and where a number is our own assumption it is labelled.

• US EPA WaterSense, Outdoor Pool Guide (PDF dated September 2022): solid covers reduce evaporation by more than 90% when in use and save 50–70% of pool heating costs for heated pools; solar (bubble) covers reduce evaporation by 50–95% depending on shape and coverage, are designed to use the sun's energy to heat the pool, and cannot serve as safety covers; 15% of US pool owners regularly use a cover (2016 study). US guidance.
• SPATA, Pool Covers: Benefits and Considerations, factsheet C15 (undated, PDF uploaded September 2020): an uncovered outdoor pool may lose as much as 90% of its heat through evaporation; a heat-retaining cover can save as much as 80% of heat loss from the pool surface; a good cover reduces humidity and almost completely stops condensation indoors; no figure for solar gain through the film.
• US Department of Energy, Better Buildings, Pool Efficiency: covers can save about 50–70% of pool heating costs; evaporation is the largest source of pool energy loss. US Department of Energy, Heat Your Water with the Sun: unglazed polymer collectors are typically used for pool heating.
• SPATA, Swimming Pool Heating, factsheet C13: collector area usually exceeds 50% of the pool surface; not always easy to hold the desired temperature in the UK climate.
• Ofgem, price cap 1 October to 31 December 2026: electricity 26.32p/kWh, gas 7.97p/kWh (goes stale on 1 January 2027). DESNZ, Solar PV cost data 2025/26: median £1,595/kW for 0–4kW installs. PVGIS v5.3: Leicester 981kWh per kWp a year.
• Price example: Amazon UK listing for a VOUNOT 8×4m solar blanket, 126 micron, £52.99, seen in a search result on 30 October 2026; a single retailer example, not an average.
• Our assumptions: an 8×4m pool at 28°C from May to September; 11,000kWh of heat uncovered and 6,600kWh covered (a 40% cut); 85% boiler efficiency; heat pump seasonal COP 4; cover price £300–£700 as a planning range.

Questions people ask

Does a solar pool cover heat the water?

Mainly it keeps heat in. Solar covers are designed to use sunlight, but the figure the US EPA gives is for evaporation, which they cut by 50% to 95% depending on shape and coverage. We found no independent UK measurement of the heat the film adds, so count the saving as heat not lost.

Do solar pool covers work in the UK?

Yes, as insulation: on our worked 8×4m pool a cover removes about 40% of the season's heat demand, worth about £413 on gas, £290 on a heat pump or £1,158 on direct electric heating. It only works while it is on the water.

Is a solar cover better than solar panels for a pool?

They do different jobs, and the cover comes first. It is far cheaper per kWh saved, and it shrinks the heating system, including the panel array, that has to replace what the pool loses.

How much does a bubble cover cost?

Prices vary with thickness and size. One Amazon UK listing we saw on 30 October 2026 was £52.99 for a thin 126-micron 8×4m blanket; we plan on £300–£700 for a thicker cover with a reel. Treat any single price as an example, not an average.