Electricity supply is a complex process involving various technologies of electricity generation and distribution. Electricity production technologies use different energy sources and therefore have different impacts on the environment. To assess the impact on the environment, we used the life cycle study (LCA) method and evaluated eleven technologies used in Slovenia. The functional unit is set at 1kWh of electricity at the consumer. The LCA model was set up in the GaBi Thinkstep program, and the evaluation of the results based on environmental indicators was performed according to the ReCiPe methodology. Hydropower and wind power plants have the lowest values of environmental indicators. Nuclear power plants, photovoltaics and natural gas also show lower values. On average, two to five times, higher values for environmental indicators are observed for thermal power plants on lignite, hard coal, biomass, and waste. The highest values were for heavy fuel oil and biogas electricity production. We additionally analysed the environmental impacts of four scenarios of electricity production in Slovenia, which relate to the closure of thermal power plant TEŠ, the construction of the second unit of the nuclear power plant Krško and the transition to renewable resources. We found that transition to renewables, compared to the existing energy mix, halves the value of climate change indicator, but significantly increases toxicity, eutrophication, acidification, land use and ozone depletion. With the second block of the nuclear power plant, however, most indicators would have lower values.