We calculate the historical payback time (PBT) and internal rate of return (IRR) for domestic photovoltaic systems installed at different times between 2003 and 2014, in three different Italian locations (North, center, South, thus representing different levels of energy yield). We show that over time, even though rather different regimes of governmental incentivization and end-user energy prices existed, such economic parameters have hardly been affected. Remarkably, this is true even for the case of systems installed in 2014 - i.e. where no incentivization of any kind is considered, but grid parity has been attained. In this case the PBT is 10.6, 9.3, 8.5 years for the locations in the North, center, and South, respectively; the IRR is 9.1%, 10.4%, 11.3%, respectively. These observations are in marked contrast with the common understanding that the dramatic reduction of installations in Italy after 2011 is due to a reduction of the economic convenience for the end-user, suggesting that the economic factor only plays a marginal role in current PV market dynamics.
