Electric energy consumed by the public lighting represents a significant item in the city public sector energy consumption structure, which includes public buildings, public transportation and public lighting. Public lighting system is one of the most important public utility activities which is under control of local governments, which pay the costs of electricity, as well as maintenance costs. Public lighting affects the quality of life of citizens in cities through, among other things, reduction of traffic accidents by up to 35%, personal safety and reduction of social approaches. Cities and municipalities in Serbia are predominately using sodium and mercury bulbs for public lighting, but have been gradually replacing them with LED bulbs in the recent years. LED technology is a satisfactory, cost-effective solution due to low energy consumption, long service life, reduced investment and maintenance costs. Thus, there is not only a reduction in energy consumption of up to 70%, but also a large reduction in CO2 emissions. The modernization of the public lighting system is, in addition to being a useful means of achieving significant energy savings, also a means of improving the quality of lighting itself. The paper shows how much it is possible to reduce electricity consumption, and thus CO2 emissions, by replacing existing lighting with LED lighting. There are 2530 light bulbs in the public lighting system of the municipality of Priboj. Until recently, mercury high pressure bulbs dominated - there were 1241 of them, compared to 743 sodium ones and 546 LED lamps. After the reconstruction of public lighting, all light bulbs are LED. The paper compares the consumption of electricity for the four months of 2019 and the same four months of 2020. It is shown that electricity consumption for these four months was reduced by an average of 55%, the average reduction in CO2 emissions was 55%, while the reduction in electricity costs was an average of 58%.