Tips for Choosing and Installing Solar Water Heaters

Consult an expert before deciding which hot water heater to purchase.

Climate considerations are very important when choosing a solar water heater, and your state government advisory centers can provide excellent local advice.

The Australian Consumer Association (Choice) provides detailed information to help you choose the best solar water heater for your location and budget.

Manufacturers and retailers may also be able to assist with detailed selection guidelines.

Choosing the Right Size

The best size for storage tanks and solar panels depends on the number of people in the home, how efficiently they use water, the climate, and the efficiency of the boiler.

Reducing your hot water demand can reduce the size and cost of the system you need.

Manufacturers or suppliers can recommend the best size for your application.

Solar Water Heater Positioning

For optimal performance throughout Australia, solar hot water systems should face solar north. The orientation can deviate up to 45° from north without a significant loss of efficiency. Use a compass to check the orientation.

For maximum efficiency, ensure that solar collectors are not shaded by nearby trees or buildings, especially in winter when the sun is low in the sky.

For optimal performance, solar collectors should be installed at an angle to the horizontal. This maximizes the annual amount of sunlight hitting the panels. It is generally recommended that solar collectors be installed at the same angle to the horizontal as the latitude at the installation site. In Australia, this angle ranges from 17.5° in Darwin to 53° in Hobart. In some cases, it may be desirable to increase the angle slightly to improve performance and reduce overheating in the summer.

In practice, many solar water heaters have been installed at the roof's slope, as it is more cost-effective and usually more aesthetically pleasing to install solar collectors flush with the roof rather than supporting use at a greater angle. Roof pitch angles in Australia are commonly between 20° and 30°, so this often reduces performance during the winter. In existing homes, the benefits usually outweigh the costs. In new homes, designing the roof areas to accommodate a suitable angle for the solar collector may be possible.

OTHER INSTALLATION TIPS

A complete thermosiphon system, when filled with water, can weigh several hundred kilograms. Most roofs can support a storage tank without reinforcement, but you should check before installation. Talk to your builder, designer, or engineer to find out.

Be sure to insulate all components, including pipes, to get the best performance from your system. This is especially important for thermosiphon systems where there is a long distance between the tank and the hot water taps. It is crucial in cold climates.

Make sure the booster control is accessible and has a visible indicator light to remind you to turn it off when not needed.

SYSTEM USE AND MAINTENANCE

Follow the manufacturer's maintenance recommendations.

Set the temperature on your booster thermostat to 60°C. A lower setting may allow the growth of harmful legionella bacteria.

In favorable climates during the summer, water temperatures in a solar water heater can approach boiling point. Heat dissipation devices may be required to prevent boiling water. It may also be necessary to install a mixing valve to reduce the water temperature at the tap to safe levels during the summer.

Perform any work requiring hot water early in the day so that the remaining water in the tank will be heated by the sun, ready for use at night.

Clean the solar panels regularly to remove dust. You can use a broom with a little detergent to scrub them.

Rinse the collectors to remove deposits. Heat pump systems do not require rinsing.

Make sure you turn the booster off when you go on vacation and consider turning it off during the summer, if conditions are favorable.