The aim of this paper is to present a new procedure for the calculation of equivalent full-load hours of operation for heating and cooling systems, from hourly temperature bin data. Following the procedure and using dry-bulb temperature bin data, equivalent full-load hours for 40 Greek cities were calculated. Results are given in tabular form and data for both heating and cooling periods are presented. For the heating period the resulted data were calculated considering a 24-h operation of the heating equipment while for the cooling period, in order to distinguish between different types of building function, data for 12 and 24 h of operation of the cooling equipment are presented. Furthermore, in order to take into account the influence of building construction, internal heat gains and indoor design temperature on the energy requirements, different balance-point temperatures are considered either for the heating or the cooling period. Equivalent full hours may be used for a rough estimation of annual heating and cooling energy requirements in buildings. (C) 2008 Elsevier Ltd. All rights reserved.