Solar pool heater guide: does it work in Canada?

A swimming pool is the easiest place to use solar heat. The water temperature you want is low, so the equipment can be simple. If you have a sunny spot and a pool that sits idle in cool shoulder months, solar heating is worth a look.

How solar pool heating works

Your existing pool pump pushes water through a set of collectors, usually black polymer panels or tubing with no glass cover. The sun warms the water as it passes through, and it flows back to the pool. A small control valve or controller sends water through the collectors only when they are warmer than the pool.

There is no glycol loop and no heat exchanger in most designs, which keeps the system cheap compared with a household solar hot water system. The trade-off is that unglazed collectors lose heat quickly on cold, windy days, so they are meant for warm-season use. For a comparison with the closed-loop systems used for domestic hot water, see how solar hot water works.

What it does for your swimming season

Expect a gain of a few degrees in summer and a longer usable season at each end. In a cool Canadian spring the water can warm up weeks earlier than without collectors, and in September it holds its heat longer. It will not turn a May pool into a bathtub during a cold week, and it will not keep an outdoor pool swimmable in November.

Results vary with these factors:

• Sun exposure on the collectors, with minimal shade between roughly mid-morning and late afternoon
• Collector area compared with pool surface area
• Wind exposure, which cools both pool and collectors
• Whether you use a cover overnight and on cool days
• Pump run time, since water only heats while it circulates

Sizing and placement

Installers often size collector area as a fraction of pool surface area. A common planning range is somewhere around half to the full surface area, but the right figure depends on your location and how warm you want the water. Ask for the assumptions behind any number. A colder region, a shaded yard or a desire for warmer water all push the area up.

Roofs facing south or close to it with a modest tilt work well, and so do ground racks beside the pool. Pool collectors are light when empty, but filled they add weight, so roof structure and mounting details matter. Our guide to roof, ground and carport mounting covers the general considerations, including snow and wind.

What it costs

Prices vary a lot by pool size, roof access and plumbing. As a rough planning idea, many residential systems fall in the low-to-mid thousands of dollars installed, in CAD, with ground mounts and long pipe runs pushing it higher. Treat that as a typical range and get written quotes. Because there is no fuel, running cost is mostly the pump electricity you would use anyway, plus a little for the controller.

Provincial or utility rebates for pool heating are uncommon, and programmes change. Verify what exists in your area before you count on anything, using the steps in our guide to checking current incentives.

Solar thermal vs a pool heat pump

A heat pump uses electricity to pull heat from the air and can run in cloudy weather and at night. Solar collectors depend on daylight. Some owners combine them: collectors do the free work on sunny days, and a heat pump covers the gaps. If you already have, or plan, solar panels for the house, a pool heat pump can partly run on that electricity. See heat pumps and solar panels together for the broader logic. The same trade-offs between thermal collectors and electricity-making panels show up in solar panels vs solar water heating.

Winter care

Unglazed collectors are not built to freeze with water inside. Before the first hard frost, they must be drained, or the system must have a proper winterizing procedure. Ask your installer to show you the valves and the steps, and to write them down. Skipping this is the most common way a pool system ends up damaged.

Check the following each season:

1. Inspect mounts and fasteners after winter.
2. Look for leaks at pipe connections and at the collector headers.
3. Confirm the controller or valve is working and set sensibly.
4. Clear leaves and debris from collector surfaces.

Is it worth it for you?

Solar pool heating makes the most sense if you have a pool that will be used for many seasons, a good sunny location and a cover you will actually use. It makes less sense for a shaded yard, a rarely used pool or a plan to swim in cold weather. In those cases, a heat pump or simply a good cover may be the better money.

If you are exploring more options in this area, the hot water and heating hub collects our guides on collectors, air heating and heat pumps. For a sense of domestic costs for comparison, see solar hot water cost in Canada. Get at least two or three quotes, ask for the expected temperature gain in your climate, and check that the installer holds the appropriate plumbing and electrical licences for your province.