Energy efficiency indicators describe the development of energy consumption in relation to a reference value. Energy consumption in this case may not be considered separately, but always with reference to either economic or structural parameters, so as to show in an exemplary way which amount of energy is needed for the maintenance of our current standard of life, or in order to demonstrate the extent to which energy consumption changes with each additionally produced item.

Generally, three types of efficiency indicators are in use:

• Economic indicators: Energy intensity, carbon intensity [kWh/EUR, CO2/EUR]
• Technical indicators: energy consumed per unit physically produced [kWh/ton, litre, etc. (Production index)] resp. specific consumption [kWh/application, kWh/residential unit, litres/km, etc.
• Diffusion indicators: market share of energy-efficient appliances, of renewable energy sources, of efficient procedures [e.g. degree of market diffusion of energy-efficient lamps, A++ appliances, solar thermal systems, modal split in (freight) transportation, etc.]