Solar hot water, explained simply
A solar hot water system heats water using the sun. Collectors on the roof absorb heat and pass it into the water, which is stored in a tank. Because the sun does not shine on demand, every system has a booster — gas or electric — that tops up the temperature on cloudy days, in winter, and when the household uses a lot of hot water at once.
Adelaide is one of Australia's sunnier capitals, and solar hot water has a long history here. Plenty of homes from the 1980s onwards still carry collectors on the roof. When those systems reach the end of their life, the question is whether to replace solar with solar, or move to a different option.
We arrange quotes through independent local plumbers who look at the roof, the existing setup and the household's needs before recommending a system.
The two main layouts
Close-coupled. The tank sits on the roof directly above the collectors. Water moves through the collectors naturally as it heats, with no pump needed. These are simple and efficient, but the tank adds weight to the roof and is in full view from the street.
Split (pumped). The collectors are on the roof, the tank is on the ground or inside, and a small pump moves water or fluid between them. These keep the roofline cleaner and the tank easier to reach, at the cost of a pump and controller that can need attention over time.
Collectors: flat plate or evacuated tube
Flat plate collectors are rectangular glazed panels. They are durable and work well in Adelaide's strong sun.
Evacuated tube collectors use rows of glass tubes with a vacuum for insulation. They tend to hold their output better in cold and cloudy conditions and can be a good fit in the Hills.
The plumber should explain which suits your roof and climate, not just what they usually fit.
Is your roof right for solar?
A good solar site has:
- North-facing roof space, or close to it, without shading from trees, chimneys or a neighbour's second storey for most of the day.
- Roof strength to carry the collectors, and for close-coupled systems the full tank of water.
- Safe access for installation and future servicing.
- Room for the tank at ground level, if it is a split system.
If the roof faces mostly south, or is heavily shaded, a heat pump is often a more practical low-emission choice.
Boosting: gas or electric
The booster decides a lot about running costs. A gas booster — either a continuous flow unit on the outlet or a gas-boosted tank — heats quickly and suits homes already on mains gas. An electric booster is simpler to install and can be timed to run off-peak or during the day from solar panels. Ask how the booster is controlled; one that runs too often can quietly cancel out the solar saving.
Frost and the Hills
In the Adelaide Hills, frosty nights can damage collectors that are not protected. Many systems include frost protection, either through a heat-transfer fluid in a closed loop or valves that release a small amount of water to prevent freezing. Make sure the quote names the frost protection method if you live in a colder area.
Incentives
Eligible solar water heaters can create small-scale technology certificates under the federal Small-scale Renewable Energy Scheme, administered by the Clean Energy Regulator. The value varies, and installers usually apply it as a discount. Check the current position and ask to see the certificate value as its own line. See the comparison guide for how solar stacks up against gas and heat pumps on running costs.