Combined heat and power

Combined heat and power (CHP) is a system in which fuel is used to create both heat and electric power. Creating high-temperature heat (e.g. hot water to heat buildings) usually results in some wasted low-temperature heat, which is simply dumped into the environment. A CHP system recovers some of this waste heat and uses it to generate electric power, making it more efficient than using two separate systems to generate heat and power.

CHP systems are generally only economical on a large scale, for example to provide heating water and power for an industrial site or an entire town. However, small CHP units for individual dwellings are now beginning to be introduced. These replace the traditional gas- or oil-fired boiler (furnace) used in central heating systems. The waste heat is recovered by a Stirling engine.