In this report we discuss the present situation of solar water heating for domestic supplies in Turkey and give the results of a computer analysis for nine distinct regions. The analyses are carried out for four typical days of the four seasons and also on a monthly base. The results show that detailed initial work must be carried out before installing the system to determine the optimized collector area. Such analysis can provide efficient using of the Sun's energy as well as economical benefits in the initial investments and long term utilization. (C) 1999 Elsevier Science Ltd. All rights reserved.