This work introduces the aspects of the proper choice of the exploitation data connected with heat supplied to a building in order to estimate the influence of wind speed, insolation or level of cloudiness on energy consumption. The analyzed building had a traditional, central heating installation with vertical risers in each flat and convective radiators and supplied with the heating medium (80/60 °C). The exploitation data from one heating season were analyzed and the influence of the wind speed within the range below 3 m/s, 3÷6 m/s and above 6 m/s on the value of the heat power delivered to the building was presented. Different times of the day and night were taken into account and the attention to the accuracy of obtained results was paid.