Solar water heating systems use solar panels, called collectors that are fitted to your roof.
These collect heat from the sun and use it to heat up water which is stored in a hot water cylinder. A boiler or immersion heater can be used as a backup to heat the water further to reach the temperature you want.
Designed right, a solar thermal system can be expected to deliver up to 60% of a homes annual domestic hot water needs. You will also qualify for the Renewable Heat Incentive (RHI)which financially rewards generation of renewable heat, please see table below. Solar Thermal systems are used as a subsidy to domestic hot water and can reduce Carbon emissions and heating bills as well as providing an income through the RHI.