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How roof mounted solar hot water works

The roof mounted system works on the scientific principle known as thermosiphon, in simple terms "heat rises".

Thermosiphon naturally occurs when the source of heat (Hot Panels) is below the stored water (The Tank).

As the Sun heats the water filled panels, thermosiphon occurs moving the hot water in a circular motion from the panels to the tank, without any mechanical parts as shown in the diagram below.

If there is not enough heat in the Sun on a particular day (extended cloudy periods and during Winter) a booster is used to top up the heat.

Most solar hot water systems use electricity to boost, however gas boosted systems are also available.

How the Sun heats water in roof mounted systems

Cold Water falls to bottom of panels (1),

The Sun heated panels (2) makes the hot water rise,


Hot water enters the tank, (3)


Siphoning/pushing the cooler water to the bottom of the panels (4) repeating the process.  

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Benefits of Roof Mounted Solar Hot Water are:

  • No moving parts to heat water

  • Lowest ongoing maintenance costs

  • Creates space at ground level