Energy use is since 2005 measured in the apartments in two multi-family houses in Vasteras, Sweden, by the housing company. The momentary power required for hot water is continuously registered in every apartment and the hourly data, which the analysis is based on, are averages of a number of such momentary measurements. Measured data from two years, 2005 and 2006, has been processed and evaluated so far and is presented in this paper, but has also been reported in [7]. Both hot water and electricity demand are measured on an hourly basis.

The two buildings comprise 24 apartments of a total area of 1894 m2, occupied by totally 40 persons (19 and 21 residents respectively). The buildings were constructed in 2001 and are provided with energy efficient facilities. Energy costs for utilities, such as heating, electricity, cold and hot water, are included in the total rent per apartment, which is the most common solution in Sweden. Therefore, the tenants are not encouraged to save energy to the same extent as households in single-family houses or apartments with individual billing. There are further plans to install individual measuring equipment for hot water and electricity in 1 300 apartments. Another 300 apartments have already been measured by the residential company, but this data has not yet been processed.

3. Results and analysis

The results have been analysed in different ways; the modelled and measured hot water demand have been compared on an annual and hourly basis to investigate the agreement and the validity of the model. Furthermore, the variation in measured hot water use on a monthly, weekly and daily basis has been investigated to enable further improvements of the model.