Solar water heaters are devices that use sunlight to heat water for residential or commercial use. They typically consist of solar collectors, which capture sunlight, and a storage tank, where the heated water is stored for later use. These systems can significantly reduce energy costs by utilizing renewable energy from the sun. There are two main types of solar water heaters: active and passive systems. Active systems use pumps to circulate water, while passive systems rely on natural convection. Both types can provide hot water for various applications, including domestic hot water, swimming pools, and space heating.