This study is a part of a project, "Providing Working Comfort and Energy Saving in Offices by Using the Control Systems" carried out by the Electrical Engineering Department of Istanbul Technical University, and aims to find out how much energy can be saved by using a daylight responsive lighting control system compared to a conventional lighting system by evaluating the collected data during one year. Data are classified as monthly, seasonal and annual. The weather conditions are considered by classifying the days as clear, mixed or overcast. Energy saving obtained by daylight responsive lighting control systems shows differences according to the months and seasons. According to these results, up to 30% energy saving could be obtained for the climate conditions similar to Turkey. 3 refs.