SummaryOverviewChemical conversion efficiencyFuel heating values and efficiencyWall-plug efficiency, luminous efficiency, and efficacySee alsoExternal linksEnergy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation), or heat. The resulting value, η (eta), ranges between 0 and 1.