Find out how solar energy can help you heat a pool

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Want to make a pool usable during cooler months? No problem: you just have to heat the water. The problem is that heating pools is expensive – perhaps more than think. The US Department of Energy estimates that for every one degree you raise the temperature of the water, energy consumption increases 10% to 30% (depending on where you live) (1). Why not adopting an ecological pool heater?


Heating an average pool (8 by 4 meters with a cover) from May to September in a temperate region, will cost anything from $400 (with a natural gas-powered system) to $700 (with oil-based heating) to $800 (with electric heating). Propane-powered heating could cost an eye-watering $1,100 (2)! Not good for your pocket – or the planet.

In France, for example, some 90% of pools, both private and public, have a heat pump that uses one of the fuels listed above (3). Eco-friendly pumps even became more popular! But there is another energy source available that’s both free and environmentally-friendly: the sun.

Today, solar energy can be used as an ecological pool heater, with new technology offering different designs and options. Let’s take a look at some of the models available.

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in the swimming pool sector

Solar panels

A popular solution, solar panels can be fixed in a sunny place such as walls or a roof. Water from the pool is pumped through the panels and passes through photovoltaic cells. As it moves, the water is heated by the sun. It then passes back into the pool, raising the temperature.

There are many designs on the market, some of which also generate electricity. These hybrid panels can not only heat the water but power the pump and filtration system. A big investment, solar panels are not the cheapest solutions on the market. This is the choice of the new ecological public pool of Holmen, in Norway!

Solar domes

A more flexible, portable option is a solar dome. These allow water to pass through a tightly coiled pipe under a plastic dome-shaped cover. Inside the dome, a ‘greenhouse’ effect occurs. The water is heated and then passes back into the pool. The dome is made of unbreakable plastic that’s resistant to UV rays, chlorine and sodium. And thanks to its shape, the dome can heat the water all day long, even when it’s not that sunny. This is because the coiled pipe offers a large surface area, allowing it to absorb as much sunshine as possible. Domes come in various shapes and sizes but roughly speaking, you’ll need one dome per 15m3 water. With the option to disconnect and move the dome whenever you want, it’s convenient as well as ecologically sound.

Solar mats and carpets

For smaller, private pools, a solar carpet could be the answer. These consist of a long pipe which winds back and forth, and is attached to a rubber mat. Water is pumped into the pipe and then heated by the sun. There’s no glass or insulation, so the heating happens slowly, in the same way as a solar-powered shower. The heated water then passes back into the pool.

Different carpet sizes will produce different results, but an increase of 10° Celsius in temperature is more than possible. A complete system will cost between $115 and $230 per m2 of carpet. But to be effective, the carpet must be 30% to 60% of the size of the pool – which is why solar carpets are more suited to smaller pools. The mat or carpet should be placed in the garden or on a roof, where it can make the most of the sun.

While a solar carpet can’t replace a conventional heating system, it can certainly be an effective way to lower heating costs. Solar carpets are robust and hard-wearing – resistant to changes in weather. They’re also supple and portable, which means they can be disconnected and stored when not in use. Simple and low maintenance, solar carpets can be highly cost-effective.

Solar pool covers

Finally, there’s the solar pool cover. Light and practical, they consist of a layer of bubbles which capture the heat of the sun. They’re placed in direct contact with the water, thereby heating the pool. The thicker the cover and the more pool it covers, the more effective it will be. Solar covers also reduce evaporation and stop the water temperature dropping overnight. But before you rush to buy one, consider the following.

Solar pool covers only work in hot, sunny conditions. On a rainy day, the pool won’t be heated. What’s more, the cover must be stored in the shade when not in use. In cold conditions it should be replaced altogether by a more robust cover or tarpaulin. It’s also important that the cover isn’t in use when the pool is being treated with chemicals. And no one should use the pool when the solar cover is in place.

Follow these precautions and a solar pool cover can share the work of an existing heating system and help you save on energy.

Curious about heating a public pool?
Discover two textbook cases combining sustainability and efficiency

Solar energy can’t replace conventional heating systems – but it can reduce heating bill. Start considering an ecological pool heater for your clients!

(1) US Department of Energy
(2) Distripool
(3) DualSun

© Photo credit: Fotolia / cobra1983

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