The split system, for example, while discrete, may not be the best option as connection costs can soar if there is a relatively vast distance between the system and the water tank it draws from. And, while roof-mounted systems are highly energy efficient, they can weigh up to 300 kilograms and can only be mounted on sturdy rooves. There can also be crane fees associated with its installation. Heat pumps, an alternative to solar hot water heater systems, do not require direct sunlight to provide a consistent supply of hot water, but they are a noisier system.

Weighing up all these options might be made a little easier with the help of the following descriptions of different types of clean energy hot water systems currently available on the Australian market.

The split-system

A split system is made up of five key pieces of equipment:

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  • Solar collectors which are mounted on the roof
  • A water storage tank, usually installed at ground level
  • A solar controller
  • A small electric pump
  • An electric or gas booster.
The electric pump circulates water from the storage tank on the ground up to the collectors on the roof, where the water is heated by warm rays from the sun. It is then returned to the water storage tank, where it stays until it is needed for use in the home.

Often referred to as an ‘active’ solar system, the split system uses an electric pump to circulate the water through the collectors. A solar controller – especially designed to avoid energy wastage and overheating water in the storage tank – decides when the pump should run.

With the water storage tank installed discreetly on the ground, split systems have minimal visual impact, particularly when the solar collectors are mounted flush with the roof. They can be installed on any roof pitch, as the pump is responsible for moving the water through the solar collector.

With this system type, non-standard installation costs may apply due to the location of the water storage tank, and the length of pipe required to move water from the water storage tank to the solar collectors. Also, if in a cyclone-prone region, the system will require increased roof fastening to withstand strong wind conditions.

The roof-mounted system

The roof-mounted system is made up of solar collectors and a water storage tank. Both of these are installed on the roof. The system’s design is based on a principle called ‘thermosyphon’. This simply means cold water is heavier than hot water, and so cold water will fall and hot water will rise. The cold water in the solar collectors receives warm heat from the sun and so it rises into the tank. This heated water displaces cold water in the tank which then falls into the solar collectors where the process continues. The hot water is stored in the water storage tank until it is needed for use in the home. Any unused water that cools in temperature simply returns back to the collectors for re-heating.

Roof-mounted systems are often referred to as ‘passive’ solar systems because they rely on the principle of thermosyphon, rather than an electric pump, to move the water through the solar collectors.

A roof-mounted system weighs several hundred kilograms, so the installer needs to check that the roof will support the extra weight. Also, if in a cyclone-prone region, the system will require increased roof fastening to withstand strong wind conditions. In some cases, a crane may be required to lift heavy components onto the roof. Costs associated with craneage are not part of a standard installation.