Solar thermal transfer systems heat drinking water in the same way as an immersion heater.

The warmed fluid from the solar thermal collectors flows through the heat exchanger, where it heats the water in the same way as a heating coil in an immersion heater would – only without electricity.

Since the solar storage cylinder is part of the domestic drinking water system, warm water is always available for baths or showers.

If there is not enough sunlight, the back-up heating system switches on.