Heating your swimming pool with solar energy is not only environmentally responsible but can extend the swimming season by four weeks.

A properly sized solar heating system will allow you to swim earlier in the spring and later into the fall, according to Natural Resources Canada.

Whether or not you have an existing heater, you can keep your pool warmer and open longer with free energy from the sun.

“When we open the pool in the springtime, the water is often frozen; the frame of the pool is frozen, as well as the ground around it,” says Colleen Simmons, owner of Enersol Solar Products, a Campbellville-based manufacturer of solar pool heaters.

“So to pour propane, gas or electric heat into your pool is a huge expense. If you’ve turned the solar on, you can heat up that mass,” Simmons says. How long it takes to heat a pool with a solar heater depends on the weather, but it’s usually about two days compared to one day for a regular heater.

Simmons says pool warming costs often rival house heating bills. Replacing a natural gas or propane heater with a solar heater could stop three to 10 tonnes of carbon dioxide from entering the atmosphere each swimming season, according to Natural Resources Canada. That’s almost the equivalent of what your car produces in a year.

The system works when water from the pool goes through a pump and filter and then to solar panels.

The panels are 1.2 metres by three metres (four feet by 10 feet). It’s best that they’re installed on the roof of your house because they also gather heat from the roof and help cool it; but they can be installed anywhere.

A sensor can tell when the panels on the roof are hotter than the pool water and then it diverts the water into the panel to gather the heat and puts it back into the pool. Simmons says pool water might circulate four to six times a day and you gain 10 C to 11 C of heat.

A system costs between $2,500 to $4,000, including installation and depending on the size of the pool.

They can be bought at stores that handle swimming pools and their maintenance products. Simmons says a system will pay for itself in about 18 months. (A conventional heater costs $1,500 to $2,000.) One drawback, she says, is it isn’t as effective on cloudy days.

“It can replace a pool heater, but some people keep their heater, so if they’re having a party on Friday and it’s been a cloudy all week, they can still throw their heater on,” Simmons says. Chris Winter, executive director of the Conservation Council of Ontario, says anything that saves energy is good.

“It’s the ecologically sound thing to do because you’re minimizing the environmental impact of your pool,” he says. “If you’re investing in a pool, you should also invest in one of them.”

Visit enersol.com for more.