Influence of the carbon intensity of electricity on carbon savings from CHP

The carbon intensity of electricity is a key input to calculations of carbon emissions from buildings, and can be decisive in the selection of low- and zero-carbon technologies. The origin of the value for the carbon intensity of electricity is not well understood and its derivation is investigated. The carbon savings from gas-fired combined heat and power (CHP) vary greatly depending on the carbon intensity of electricity. The current debate about the effectiveness of CHP centres on detailed considerations about which values for the carbon intensity of electricity should be used. The expected future decarbonization of the electricity supply grid would considerably reduce carbon intensities, thus the longer-term trends in carbon intensity and their effect on the carbon savings from CHP are of greater importance. A new expression has been developed to describe the carbon savings from CHP and trigeneration as a function of varying carbon intensity of electricity. While CHP can offer limited carbon savings in the short-term, the future decarbonization of the electricity grid means that CHP will soon be among the most carbon-intensive technologies, and the use of trigeneration will cease to provide carbon savings even sooner.