Annual billing of heating and hot water reduces energy use by roughly 20 percent. In addition to this 20 percent reduction, by providing apartment users with regular subannual consumption information, it is possible to reduce annual heating and hot water consumption by a further 7 to 12 percent. The studies listed on this page provide evidence of a long-term savings effect if users are provided with information on their consumption that illustrates the effects of their heating habits close to the time of use, and they adjust their behaviour accordingly. Both the energy source and the format in which the information is provided are largely irrelevant to the magnitude of this effect. It’s for precisely this reason that the European Energy Efficiency Directive (EED) mandates transparency for consumers through sub-metering.