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The importance of follow ups of buildings energy use during operation to optimize the performance and identify deviations and errors has attracted attention during recent years. The use of heating varies from year to year even for reasons other than the outdoor climate, which means that if an energy simulation is to be verified, this must be done over several years in order to take the yearly variations into account. As buildings are becoming more energy efficient, space heating is becoming an increasingly smaller part of the total heating energy while the user determined hot water heating part is increasing and is often greater than space heating. Unfortunately, it seems that enough knowledge, studies and data that describe how the domestic hot water heating varies between different years are lacking. A particularly low or high energy use during a certain year might be due to stochastic variations. This energy use would not be representative of several subsequent years. This might explain parts of the reported gaps between calculated and measured energy use. Furthermore, this must be taken into consideration before measures are executed in the building in order to avoid errors and investments that are not justified over time. To supply the industry with reference data on typical variations during time and between different users, there is a need for several years of measurements of domestic hot water heating in the same apartments in a large enough sample of apartments to obtain good statistics. Domestic hot water heating has been measured in 539 apartments in 37 multi-family buildings in Sweden during six years. This article presents statistics and characteristics of the use of domestic hot water and the variation between years and between different apartments and buildings.

Citation: ASHRAE Papers: 2015 ASHRAE Annual Conference, Atlanta, GA