CWA 45547:2004

CHP can make significant fuel and emissions savings over conventional, separate forms of power generation and heat-only boilers. The generation of electricity from power stations is generally at efficiencies in the range 30-55%, based on the Net Calorific Value (NCV) or Lower Heating Value (LHV) of the fuel. Further losses occur in the transmission and distribution of electricity to customers. This means that 45-70% of the energy content of the fuel is not usefully employed. This unutilised energy content is rejected as heat directly to the atmosphere or into seas or rivers. The generation of electricity and the recovery of heat in CHP plants typically achieve overall efficiencies of 70-90% and above, corresponding to efficiencies of heat only boilers. The higher the overall efficiency and the power to heat ratio, the more effective the CHP process.