Combined Heat & Power (CHP) is a method of providing both electrical power and, as a by-product, hot water.

The CHP unit is in simple terms a large natural gas fired engine, very similar to that of a standby generator; it is generally sized to provide a major portion of the electrical load required by the building. This electrical load would be met by the alternator on the engine and would on average provide around 90-95% of the electrical requirements of the building. An ideal situation would be that of a hospital or multiple use district heating scheme requiring a continual load.

As the engine runs, heat is generated and needs to be cooled in order to keep the engine at a suitable constant temperature of around 90°c to avoid overheating and potential damage to the unit. This heat can be harnessed to provide hot water to the building to serve LTHW heating or primary hot water for domestic use. Excess heat (if any) is then discharged via a fan assisted radiator or ‘heat sink’, in a similar principle to that which is found in a family car.

To achieve the maximum efficiency from the system the CHP is required to run for as long as possible with a continual, near maximum demand for electrical power and a reasonable demand for the ‘free’ heat produced in the combustion process.