The use of polymer materials for photovoltaic applications is expected to have several advantages over current crystalline silicon technology. In this paper, we perform an environmental and economic assessment of polymer-based thin film modules with a glass substrate and modules with a flexible substrate and we compare our results with literature data for multicrystalline (mc-) silicon photovoltaics and other types of PV. The functional unit of this study is ‘25 years of electricity production by PV systems with a power of 1 watt-peak (Wp)’. Because the lifetime of polymer photovoltaics is at present much lower than of mc-silicon photovoltaics, we first compared the PV cells per watt-peak and next determined the minimum required lifetime of polymer PV to arrive at the same environmental impacts as mc-silicon PV. We found that per watt-peak of output power, the environmental impacts compared to mc-silicon are 20–60% lower for polymer PV systems with glass substrate and 80–95% lower for polymer PV with PET as substrate (flexible modules). Also in comparison with thin film CuInSe and thin film silicon, the impacts of polymer modules, per watt-peak, appeared to be lower. The costs per watt-peak of polymer PV modules with glass substrate are approximately 20% higher compared to mc-silicon photovoltaics. However, taking into account uncertainties, this might be an overestimation. For flexible modules, no cost data were available. If the efficiency and lifetime of polymer PV modules increases, both glass-based and flexible polymer PV could become an environment friendly and cheap alternative to mc-silicon PV. Copyright © 2009 John Wiley & Sons, Ltd.