The energy certificate is a multi-page document that evaluates real estate energetically by calculating the energy efficiency of the property. Since this calculation is based on standardized calculation methods, the energy pass offers potential buyers and tenants the opportunity to compare the energy consumption of real estate and to calculate the associated costs. For homeowners, the energy certificate has the advantage of being able to see the current energy status of your property and, if necessary, to carry out modernization measures in order to optimize energy efficiency. Modernization measures, such as the replacement of heating systems or the insulation of external walls, should be carried out if there are energetic deficiencies, which are indicated by the red area of the color scale. The possession of an energy certificate has been mandatory since October 1st, 2008. This means that owners who want to sell or rent out their property not only have to provide the energy performance certificate when placing the advertisement on the Internet, but also have to have them to hand when viewing the property. Caution: If the owner does not present the energy certificate when selling or renting a property, this can be punished with a fine of up to 15,000 euros. It should also be noted that there are two types of energy performance certificate: the requirement certificate and the consumption certificate. Both certificates are valid for 10 years and can be reissued if renovation work and renovation measures change the energy status of a property.