Energy-efficient heating / Domestic Hot Water (DHW) requires close control of both time and temperature. Thermostats limit fuel consumption and enhance comfort by controlling the temperatures of air within dwellings, and their stored domestic hot water, at desired levels.

Most electronic thermostats are battery powered, allowing simple two-core output wiring and no neutral connection. Radio Frequency RF models transmit radio signal commands to other control system components via adjacently sited receiver/switching units.