This study examines and compares the energy consumption of 15 residential buildings by evaluating the energy bills of the past seven years (2011-2017). The resulting consumption data are compared with the calculated demand values from the respective energy certificates. The informative value of the energy performance certificates is checked in this way and analyzes of deviating results are made. Furthermore, the energy costs for heating and hot water are taken from the bills and then the influence of various parameters and characteristics of the objects on their total costs are examined. The examined residential buildings are located in the metropolitan area of Vienna and form a mix of different building and energy classes, years of construction, size of apartment and number of residential units per object or component. In the present study, the consumption data of 1348 apartments, which are divided into a total of 49 components, are statistically recorded and evaluated. These objects provide a overview of the consumption behavior of the residential buildings themselves, as well as the user behavior of the respective units and are to be understood as a survey of the current consumption situation and the resulting costs.