A solar water heater is a solar-powered device that utilizes the energy from the sun to heat water. Ideally, it consists of a system installed on the rooftop that collects the incident sunlight which is then used to heat water stored in an insulated tank.
This system isn't connected to a power supply and hence doesn't have an on-off switch. The sunlight it collects throughout the day is used for heating the water tank. Then, this water can be used for any application as desired.
A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications