Oil shale has a major role in Estonia's energy supply. This paper gives a brief analysis of indicators on efficiency and on environmental impact of the energy sector in Estonia. A more detailed overview is given oil emission of greenhouse gases and on relevant possibilities of their reduction. Increase in energy efficiency is an important factor for the energy usage but also for the economic development of society. Therefore an overall assessment of trends on the national level is given, and a brief comparison with relevant indicators in other EU member states is presented.