Operation temperature of solar heating systems makes the use of a radiant floor to transfer heat into the conditioned spaces suitable. Performance data related to solar heating systems are scarce. Knowledge of these data is important to establish control strategies that lead to an optimal operation of these systems. The objectives of this study were to acquire and analyse the performance data of a residential solar heating system in Murcia (Spain), and to compare the recorded data with the performance estimate provided by the f-chart method used for sizing the system. The solar fractions registered in the system during the months of January and February 2004 were 20% lower than those predicted by the f-chart method. This lack of coincidence was assumed as inherent to the f-chart method. (C) 2005 Elsevier B.V. All rights reserved.