Building energy consumption readings can be obtained from different sources. Building energy certificates, for example, show the overall primary energy requirements, further broken down into consumption and demand-based certificates.

Data on heating, hot water preparation, cooling, ventilation and built-in lighting are needed to derive consumption-based energy certificates in non-residential buildings. Consumption data can be found on heating bills, supplied by the landlord/energy supplier, or carried out by relevant service-providers, and must cover at least the three previous calendar years. The consumption is indicated in kilowatt-hours per year in terms of the net floor area (metres square).

In addition, consumption figures are divided according to heating energy and electricity. The heating value includes weather-compensated energy consumption (even if the energy source is electricity) and, where applicable, the energy consumption for water heating when the systems are connected to one another. The electricity value records the electricity consumption components for cooling, ventilation, built-in lighting as well as electrical auxiliary energy for heating and central water heating. Supplementary electric heaters and decentralised water heating are also taken into account.

For a demand-based certificate (e.g. new buildings), the energy balance is determined as a function of the boundary conditions of the building, technology/devices installed, and the primary energy requirements. Doing this, the energy requirements of heating, ventilation, air-conditioning, drinking water supply, and lighting are all considered. The preliminary standard DIN V 18599, which consists of 12 parts, explains the calculation methods in corresponding main topics.