Cost, performance, and yield comparison of eight different micro-inverters

To investigate efficiency and yield of most micro-inverters available on the world market in 2013-14, an outdoor test field on the University of Paderborn has been set up. The inverters have been fed by identical & calibrated crystalline silicon PV modules of 215 W at STC. To monitor accurately AC power output and yield, each of the micro-inverters has been equipped with a calibrated precision electricity meter. For micro-inverters that require control units for grid-feeding this has been purchased also. The test field is equipped with pyranometers in the module plane for global and diffuse irradiance, temperature, wind speed and wind direction measurement. The comparison includes energy yield over almost one year, efficiency-load characteristics, recovery times after switch-off, cost comparisons (including control units necessary and wiring), basic safety, reliability, warranty duration comparisons, and lifetime costs for generated electricity. While the market is quite new, the range of purchase costs varies considerably between the models in comparison, sometimes inverter costs are higher than module costs.