Lighting systems are used in all building types and consume large amounts of energy as well as adding to carbon dioxide (CO2) emissions. The aim of this research was to analyze energy consumption in the lighting systems of a new building. This study conducted a preliminary energy consumption audit of the Faculty of Science on the Kasetsart University Sriracha Campus, Thailand. The actual energy consumption in the study period and the specific energy index (specific energy consumption) were assessed. The results showed that the total electric power of all bulbs in the building was 72.13 kW and about 74 % were 20 W lamps. Annual energy consumption and carbon dioxide emissions were 157,753.73 kWh and 89,477.92 kg carbon dioxide for 9 hours use. The total energy consumption accounted for 1.64 % and 4.37 % based on 9 and 24 hours operation, respectively. The specific energy index was higher than the average for this university. Therefore, the energy consumption data obtained are very important in developing energy-saving measures.