These are typically mounted on a roof. The heated liquid – often a glycol mix to prevent freezing - is circulated by pump to a coil in the domestic hot water cylinder, or to a thermal store for contribution to a heating system.
The systems can be applied to individual homes or to a large central plant, and can be an effective carbon reduction method.
According to the Energy Savings Trust, the financial savings are moderate as a solar water heating system could meet most of a home's hot water needs in the summer but much less during colder weather. However systems can save up to 580 kg of CO2 emissions, depending on what fuel is being replaced, and maintenance costs for solar water heating systems are generally very low.