The following paper presents how life cycle assessment (LCA) helps to establish the environmental impact of energy production of three Polish power plants. Ecological differences between discussed power plants as well as reasons for such differences have also been pointed out. The calculations were based on the assessment procedure of Eco-indicator 99, which allows for the presentation of the impact results with respect to three damage categories. The study also determines actions which, if undertaken, will reduce the negative environmental impact of energy production. Even though coal-fired energy production is ecologically harmful, implementation of modern technologies allows for reduction of raw material consumption and limits greenhouse gas emissions.