An energy system is a system primarily designed to supply energy-services to end-users.[1]:941 Taking a structural viewpoint, the IPCC Fifth Assessment Report defines an energy system as "all components related to the production, conversion, delivery, and use of energy".[2]:1261 The field of energy economics includes energy markets and treats an energy system as the technical and economic systems that satisfy consumer demand for energy in the forms of heat, fuels, and electricity.[1]:941
