Energy payback time and carbon footprint of commercial photovoltaic systems

Energy payback time and carbon footprint of commercial roof-top photovoltaic systems are calculated based on new 2011 manufacturers' data; and on 2013 equipment manufacturers' estimates of “micromorph” silicon photovoltaic modules. The energy payback times and carbon footprints are 1.96, 1.24, 1.39, 0.92, 0.68, and 1.02 years and 38.1, 27.2, 34.8, 22.8, 15.8, and 21.4g CO2-eq/kWh for monocrystalline silicon, multicrystalline silicon, amorphous silicon, “micromorph” silicon, cadmium telluride and CIGS roof-top photovoltaic systems, respectively, assuming a poly-silicon production with hydropower; ingot-, wafer-, solar cell and module production with UCTE electricity; an irradiation on an optimized-angle of 1700kWh/(m2×year); excluding installation, operation and maintenance and end-of-life phase. Shifting production of poly-silicon, ingots, wafers, cells and modules to China results in similar energy payback times but increases the carbon footprint by a factor 1.3–2.1, depending on the electricity intensity of manufacturing. •Energy payback times and carbon footprints range 0.68–1.96 years and 15.8–38.1g CO2-eq/kWh (hydropower/UCTE electricity, 1700kWh/m2year).•Assuming production in China results in similar energy payback times but increases the carbon footprint by a factor 1.3–2.1.•New data are used for production of monocrystalline-, multicrystalline, amorphous silicon-, micromorphous silicon-, cadmium telluride- and CIGS-PV modules.•The analysis is performed for roof-top photovoltaic systems excluding installation, operation and maintenance and end-of-life phase.