24 apartments of different size in Vasteras, Sweden were thoroughly investigated with respect to consumption of electricity/hot water during a period of six/two years, respectively. Questionnaires were answered by 19 of the 24 households, and correlations between their energy consumption and behaviour were determined. A total of 40 tenants occupied the apartments (mostly two persons per apartment), and no single individual was below 18 years old. Despite the similar conditions significantly large differences (up to ten times) were registered between households with the same apartment size and number of inhabitants for both hot water and electricity. Consumption patterns are presented in this work as well as how different behaviour variables determine energy saving potential. Analyzing the results, it can be concluded that the most important variable to explain the difference in energy consumption was the household income. Families with high income had high consumption while those with low income stayed at home much longer time every day, were watching TV more, but still consumed less. On the other hand, behavioural characteristics of electricity consumers are not applicable to the respective consumption of hot water. Therefore, different approach should be applied when developing saving strategies for different energy-derived products.