Solar hot water is water heated by the use of solar energy. It is a system generally composed of solar thermal collectors and a fluid system to move heat from the collector to the point of usage. (A collector is fastened to the roof of the building or on a wall facing the sun. In some cases, it may be freestanding.) Solar hot water may use electricity for pumping fluid and the system may have a reservoir or tank for heat storage. Systems run in two ways: active (which requires a pump) and passive (which relies on convection or a heat-pipe).
Solar hot water harvests more energy than solar photovoltaic and has up to three times the efficiency producing energy from the sun. It can also be substantially cheaper and can offer long-term performance with low maintenance. Solar hot water heaters can shave up to 60-70% off water heating costs. Another benefit may be federal, state, and utility incentives.