Cogeneration (or CHP) is the process of simultaniously generating electricity and domestic heat through the use of a combined electrical and heating unit. It's a mature tecnology widely used in the industry in which the heat recovery in the energy generation process allows for very high gloval eficiencies, with yields of 80 to 95% in the case of cogeneration centrals, depending on the aplications. Residual heat is generally used for heating, although at moderate temperatures (100-190ºC) it can also be used in absoprtion chillers for cooling. A production unit that produces electricity, heat and cold is also known as a trigeneration. The advantage of a cogeneration process is that it allows for a thermodinamically efficient way of using fuel, 

The advantage of the cogeneration process is that it recovers the residual heat from from the thermodinamic electricity production, thus making it a thermodinamically efficient way of wasting fuel. In cogeneration systems, the quantity of fuel used for the simultaneous generation of electricity and thermal energy is inferior from what would be used in convencional separate systems of electric and thermal generation.

Cogeneration capacity can be scaled to mostly satisfy the needs for heat or as generating electricity with use of the residual heat. However, a cogeneration plant biomass must be considered and specified preferably in terms of their heat production capacity and not in terms of electrical output as it is easier, if required, acquire electric power to dissipate heat efficiency of one cogeneration system is greater the closer is the site of use of the heat.

A cogeneration unit can be adjusted to either function primarly as a heating unit or as a electricity generator with use of the residual heat. However, a heating specialization should be preferably considered over the electric counterpart since it's easier to acquire energy through the heating unit rather than dissipating heat through the electric unit. A cogeneration system is more efficient the closer it is to the area in which the heat will be useful.

The various types of cogeneration plants are classified as:
Central turbine using the waste heat in the exhaust gas turbine.
Combined cycle plants adapted to cogeneration.
Plants with steam turbine using the heating system as a vapor condenser for a steam turbine.
Fuel cells have a hot exhaust, very suitable for heating.

For electrical power outputs exceeding 1-2 MWe the conventional steam turbines are used with reasonable efficiency. Alternatively gas turbines, obtained through the gasification of the biomass, can also be used.

Large scale cogeneration exists for some time already, while microgeneration is a recent development.