How solar water heaters work
By Cheryl Madliger • Bankrate.com

If you think solar water heating is an option reserved for our neighbours to the sunny south, you're not alone. "The average consumer feels [solar water heaters] don't work in the winter, when in fact that's no longer the case," says John Rood, owner of Zolarayz, a Woodstock, Ont.-based company specializing in solar thermal water heating systems. "There are some very, very efficient collectors on the market that will get really hot, regardless of whether it's January or July," he says, ensuring that environmentally-friendly solar water heating systems are an option for Canadians.

So, if you're considering making the switch, what do you need to know and what kind of savings can you expect?

How it works
Solar water heating is simple and works on top of your existing system, says Julia Roberts, manager of SolarBC, a British Columbia-based organization that promotes solar energy and runs solar water heating pilot programs. "It's a pre-heat to your regular hot water tank," she explains.

While there are three-season models on the market, a better option for our climate is a four-season model that uses antifreeze to function year round regardless of the temperature outside.

There are two different styles that work well in Canada: Evacuated tube systems use a group of individual tubes containing a solar material, while flat plate systems use a flat black solar plate attached to one or more tubes covered by a clear glass pane. When the sun's rays beat down onto the collector, which requires about 6 square metres of unshaded south or slightly southwest- or southeast-facing roof, a liquid is heated. In Canada, the liquid is usually propylene glycol, a food-grade antifreeze, also used in products like toothpaste.

The heated liquid travels from the collector to an insulated storage tank, usually located close to your pre-existing water tank, where it stays until you need it. At that time, heat from the fluid is transferred via a heat exchanger into your regular household water.

Though the acidity of the glycol should be tested regularly, Rood says maintenance of a solar system is relatively simple. "The antifreeze has to be changed probably every six or seven years," he says. "Other than that, there's really no maintenance."

Cost and savings
Storing pre-heated water means regardless of weather conditions or time of day, your existing system works less. "Your hot water heater doesn't have to turn on nearly as much as it would if you didn't have solar, so the burner in your hot water tank that heats up your water runs maybe 50 per cent less," says Jason Levesque, engineering manager at Blackstone Solar, Inc., a division of Toronto-based Blackstone Energy Services Inc.