The strong growth of the PV market is accompanied by an increasing number of “new” PV technologies and concepts now mature for commercialization. A correct calibration of these devices is in some cases very difficult, because indoor and outdoor performance measurements often lead to different results. In this paper we compare the indoor and outdoor performance measurements of a set of recent commercially available PV modules (conventional and high-efficiency c-Si, single-, double-, and triple-junction thin film (TF) technologies) and we observe that the maximum power Pmax of some devices measured indoors using our large area pulsed solar simulator is usually lower than the power measured outdoors under natural sunlight. The major effects which lead to these discrepancies are identified, as follows: (a) spectral mismatch errors, very significant for CdTe, and all a-Si TF technologies; (b) measurement-related sweep-time effects, which seem to strongly influence the performance of high efficiency c-Si devices and to a lesser extend of all a-Si TF technologies; and (c) short-time light-soaking effects, which influence the performance of CIS and to a lesser extent CdTe. Copyright © 2010 John Wiley & Sons, Ltd.