Patent ID: 7792659

Claim:
A device for measurement of energy consumption for heating tap water in a district heating substation, the device comprising: first means for measuring a first temperature (Ts) in a supply pipe, second means for measuring a second temperature (Tr) in a return pipe, means for measuring a total flow (V) of supplied district heating water to the district heating substation by means of a flow meter arranged at the supply pipe or the return pipe, means to calculate the total power (P) delivered to the district heating substation based on the measurement of a first temperature (Ts), the second temperature (Tr) and the total flow (V), a first heat exchanger for household heating, a second heat exchanger for heating tap water, the device comprises a detection means for detecting start, stop and duration of a deviation in the power usage of the district heating substation related to hot water usage, a calculation means, to calculate the energy consumption in the second heat exchanger, which relates to the deviation, the calculation means approximates the power (Pheat) usage in the first heat exchanger during the detected hot water tapping and calculates the power usage (Ptap) in the second heat exchanger for heating tap water, during the identified deviation as a difference between a total power (P) and an approximated power usage for building heating (Pheat) during a duration of a detected tapping.