This guideline applies to the distribution of costs in heat supply systems. The cost for the energy used by, and for the operation of, heat supply systems must be distributed both independent on consumption and consumption-dependent. The guideline deals with the separation of costs in installations which serve to heat rooms as well as potable water. This guideline is the first standard to offer a method that can be applied to distribute the cost incurred by complex systems. Systems where the cost for energy is billed directly by the energy provider based on an agreed tariff are not covered by this guideline.