In this paper we compare our estimate of energy consumption for domestic hot water production in a building with the measured value. The energy consumption for hot water production is estimated from the measured total power consumption. The estimation method was developed using computer simulations, and it is based on the assumption that hot water production causes rapid and detectable changes in power consumption. A comparison of our estimates with measurements indicates that the uncertainty in estimation of hot water energy consumption is +/- 10%. Thus, the estimate is comparable to class 3 energy meter measurements, which have an uncertainty of +/- 2-10%. (c) 2008 Elsevier B.V. All rights reserved.