Solar Water Heaters (SWH's) is the conversion of sunlight into heat for water heating using a solar thermal collector. A variety of configurations are available at varying costs to provide solutions in different climates and latitudes. SWH's are widely used for residential and some industrial applications.

A sun-facing collector heats a working fluid that passes into a storage system for later use. SWH's are active (pumped) and passive (convection-driven). They use water only, or both water and a working fluid. They are heated directly or via light-concentrating mirrors.

They operate independently or as hybrids with electric or gas heaters. In large-scale installations, mirrors may concentrate sunlight on a smaller collector.