Solar pool heating explained: how it works, sizing and upkeep

Solar pool heating pumps pool water up through collectors on your roof, lets the sun warm it, and sends it back to the pool. A controller only sends water up when the roof is warmer than the pool. On the Sunshine Coast it is a way to stretch the swimming season on sunny days. It is not a thermostat that holds a set temperature on demand.

What is solar pool heating?

Solar pool heating is a system that uses the sun’s heat, collected on a roof or rack, to warm the water your filter pump is already circulating. The IEA Solar Heating and Cooling Programme describes a simple unglazed system as the pool pump plus two heat sensors wired to a solar controller. It works in three steps:

1. Collect. One sensor reads the collector or roof temperature and the other reads the pool water temperature.
2. Heat. When the roof is warm enough, according to the IEA, the controller signals a motorised valve to send pool water through the collectors, where it picks up heat before returning to the pool.
3. Control. When the roof cools, the controller stops sending water up. A vacuum break valve, which Sunlover’s installation manual says must be fitted, lets the water drain back to the pool when the system switches off.

So yes, solar can heat a pool, but only while there is solar gain. Sunlover’s Heat Command manual says its controller runs the pump based on solar gain, meaning when the sun is shining and the roof is hot. Treat solar as a season extender, not a thermostat.

Strip or matting collectors vs rigid panels: what’s the difference

Strip collectors and rigid panels differ in how they are laid and fixed to the roof, as the table shows. The IEA notes that collectors used only above freezing can be made from lower cost materials such as thermoplastic rubber or polypropylene, and that open, unglazed collectors are the most efficient and cost effective choice for comfortable water in mild weather. Glazed collectors exist too, but the IEA says they often cost several times as much as unglazed systems. The table compares the two common types using Sunlover’s Australian installation manuals; neither suits every roof.

Is your roof suitable? Orientation, tilt, shade and area

Your roof suits solar pool heating if it faces roughly north, gets sun for most of the day and has enough clear area for the collectors. The IEA says collectors in the southern hemisphere should ideally face due north and can usually sit within about 15 degrees east or west with little loss. Sunlover’s strip manual prefers north and accepts north-west or flat; its panel manual ranks north, flat, west then east, and says panels should not face south. The IEA’s siting test is unobstructed sun from 8 am to 4 pm in the heating season.

Tilt follows latitude. The Bureau of Meteorology lists Sunshine Coast Airport at 26.6 degrees south, and the IEA rule is latitude minus 10 to 15 degrees for summer heating and latitude itself for year-round heating. On the Sunshine Coast that works out to roughly 12 to 17 degrees for summer and about 27 degrees for year-round use. The IEA adds that you can make up for a less than ideal angle or direction by adding collector area.

For sizing, the IEA says the system depends on sunshine, wind, regional temperatures, orientation and angle, and tells owners to get a proper sizing calculation from a local supplier. The IEA notes collectors can also be mounted on a deck, a rack or the ground, which can help where the roof is shaded or faces south.

How much warmer and how much longer can you swim on the Sunshine Coast?

How much solar adds depends on your collector area, roof and pool cover, so this guide does not give a single figure; treat any fixed number of months or degrees as an estimate to check with the installer.

The local climate explains why solar works well for part of the year and struggles in the rest. Bureau of Meteorology averages for Sunshine Coast Airport show a mean maximum air temperature of 29.1 degrees in January falling to 21.2 degrees in July, with a July mean minimum of 9.7 degrees. These are air temperatures, not water temperatures; energy.gov.au says a bubble cover can reduce cooling by 3 to 4 degrees. February is the wettest month on average, and collectors gather less heat on rainy, overcast days.

The fair way to judge a quote is to ask the installer to put their estimate in writing: the expected temperature gain for your pool area, with and without a cover, and which months it applies to. If the answer depends on a cover, a cover belongs in the plan.

Is solar enough on its own? A decision table by swim goal

Solar on its own suits owners who want warmer water on sunny days; it cannot hold a set temperature whenever you swim. The Australian Government’s energy.gov.au says that if you need heating, solar is cheaper to run than electricity or gas. The trade-off is control: solar only works with solar gain. Some controllers, such as Sunlover’s Heat Command 5SV, run rooftop solar together with a heat pump or gas heater on a shared heating circuit, so you can have both.

If you already have solar and wonder whether to add a heat pump, ask whether you need cold-season swimming or a fixed temperature. Our pool heat pump guide covers sizing and running, and the cheapest way to heat a pool in Australia compares running costs across heating types.

Installing solar pool heating: what a DIY kit covers and what needs a licensed pro

The IEA says the systems are easy enough that many pool owners can install them themselves, but the risky parts of the job are roof work and electrical work. Sunlover’s kits leave out the PVC pipe, and a new system also needs a solar boost pump and a digital controller bought separately. Sunlover’s strip manual warns that unless you have working-at-heights safety equipment, you should employ someone with the experience and equipment to finish the install, because falls from heights can cause serious injury or death. Safe Work Australia names falls as the major cause of death and injury when working on roofs, lists wind and rain as hazards, and says to treat every roof as fragile until a competent person confirms otherwise.

• Owner-safe: measuring the pool surface area, checking roof direction and shade from the ground, getting a supplier sizing calculation, and choosing a controller.
• Experienced installer: laying collectors, roof penetrations and fixings, strapping panels for wind, and pipe runs to the roof. The IEA says the system should meet local building requirements, so ask your installer or council what applies.
• Licensed electrician: Sunlover’s controller plugs into a power point and the pump plugs into the controller. If you need a new outdoor power point, or anything is hard-wired, Queensland’s Electrical Safety Office says a licensed electrician must connect it, and DIY electrical work is illegal.

Getting the most from solar: controllers, pump run times and pool covers

You get the most from solar pool heating by running the pump while the sun is on the roof, keeping the controller’s sensors accurate and covering the pool when nobody is swimming. Sunlover’s manual says that when solar is plumbed through the filter system, the filter pump must run alongside the solar pump. energy.gov.au still recommends a timer and the lowest pump speed that keeps the water hygienic, so set your timer to cover the sunny hours and ask your installer what speed the pump needs to lift water to the roof. Our variable speed pool pump guide explains speed settings.

Sensor placement matters: Sunlover says the roof sensor must not be shaded or fitted on the collector itself. For covers, the IEA calls a cover the easiest way to lower pool heating costs, and says reducing heat loss first means you can buy a smaller solar system. energy.gov.au says bubble covers can cut heat losses from a heated pool by as much as 75%, and translucent bubble covers can warm a pool by as much as 7 degrees. See whether a pool cover is worth it and the pool covers range.

Solar pool heating maintenance: owner-safe checks vs when to call a technician

Solar pool heating needs regular checks from the ground plus a periodic professional service on the roof. Sunlover recommends regular servicing to catch problems that develop over winter before the swimming season, and its rigid panel warranty requires a service at least every 12 months, so check your own brand’s warranty terms. energy.gov.au says a clean filter and clean skimmer and pump baskets reduce the work the pump has to do.

Safe Work Australia’s first control for falls is to avoid working at height, so do these checks from the ground and leave roof access to a professional. If you are in Noosa, Maroochydore or Caloundra, Billabong Pool Service can talk through your heating options on its pool heating page.