In Slovenia, electricity is generated from many different renewable and non-renewable energy sources. Every source of energy has a different environmental impact. The question arises as to what and how big this impact is. In the presented thesis we investigate and compare the impact of individual source of electricity on the environment in Slovenia. The comparison is based on the life cycle analysis. In GaBi Thinkstep program we use methods CML2001, AWARE, primary source consumption analysis and analysis of emissions of PM particles into the atmosphere to analyze impacts. The results of analyzing several different environmental impacts show that non-renewable sources of energy are not the only pollutants, but renewable energy sources also importantly contribute to pollution. The results also show that when analyzing environmental impacts, it is important to consider the entire lifecycle of production of energy, from mining of raw materials to degradation or reuse.