This European Standard provides a general approach for energy efficiency and energy savings calculations with top-down and bottom-up methods. The general approach is applicable for energy savings in buildings, cars, appliances, industrial processes, etc. This European Standard covers energy consumption in all end-use sectors. The standard does not cover energy supply, e.g. in power stations, as it considers only final energy consumption. This European Standard deals with savings on energy supplied to end-users. Some forms of renewable energy "behind-the-meter" (e.g. from solar water heating panels) reduce supplied energy and therefore can be part of the calculated energy savings. Users of the standard should be aware that this renewable energy behind the meter can also be claimed as energy generated. The standard is meant to be used for ex-post evaluations of realised savings as well as ex-ante evaluations of expected savings. This European Standard provides saving calculations for any period chosen. However, short data series may limit the possible periods over which savings can be calculated. The standard is not intended to be used for calculating energy savings of individual households, companies or other end-users.