This report provides an overview of the current and future environmental impacts of different photovoltaic (PV) technologies. Crystalline silicon PV systems currently have energy pay-back times of 1.5-2 years for South-European locations and 2.7-3.5 years for Middle-European locations. Clear prospects for a reduction of energy input exist for silicon technology, and an energy pay-back of 1 year may be possible within a few years.