Six-years-long effects of the Italian policies for photovoltaics on the pay-back period of grid-connected PV systems installed in urban contexts

In this study the discounted pay-back (DPB) period of rooftop photovoltaic (PV) systems installed in urban contexts was investigated during the course of time with the aim of evaluating the effects of the different supporting policies enacted by the Italian government. The profitability of the investment in three Italian cities was observed from June 2010 to May 2016 by means of an exhaustive economic analysis based on the study of the variation of the costs and benefits during the lifetime of the investment. The analysis considered the disbursements for the PV system devices, maintenance and management, insurance, and wear of PV panels and inverters. Other significant parameters, such as the degradation rate in the efficiency of the PV panels, the discount rate, the inflation rates and the revenues from the sale of the energy exported to the grid and the reduced electricity bills were also taken into account. Compared to the feed-in tariff (FIT) and premiums mechanism in force in Italy until July 2013, the current tax credit program has determined shorter values of DPB periods, which, depending on the site latitude, range from 7.44 to 12.78 years at the end of 2015.