Economic analysis of investment in the rooftop photovoltaic systems: A long-term research in the two main markets

Nowadays, due to incentive policies, the PhotoVoltaic (PV) installations become an economically attractive investment. The different policies aim to reduce the PV installation costs, consequently to the deployment of the market. In recent years, a progressive price decrease of components for PV installations has occurred, according their learning curve: every doubling of the volume implies approximately a cost reduction of −20%. In order to reduce the burden of the incentive rate on the national budget, maintaining the economic margin of the investment attractive for investors, a progressive tariff decline has also taken place. This paper provides a technical-economic analysis of investments in PV systems installed on the rooftop, considering incentive policies, and applies it to some significant case studies in the Countries, in which PV market is the most prosperous (Germany and Italy). The analysis puts into evidence the past and current economic margins of the PV investments since 2006 to 2012. Four case studies from 3 kWp to 1 MWp are examined in detail. The profitability indexes in terms of net present value and internal rate of return, evaluated throughout incentive duration of 20 years, become very interesting above all in Italy (higher than 100% of the installation cost and higher than 10%, respectively) since 2009, when an abrupt decrement in installation cost occurred. In Italy the best profit margins occur for large-size PV plants and are poorly counterbalanced by the decline of the feed-in tariff up to 2012, when a new framework has given a knock to the investments, whereas in Germany the best margins happen for medium-size PV plants and are well adjusted by the feed-in tariff. However, it is predictable that a cut in German feed-in tariff will take place, because the profit margins have been higher in last year than in the previous years.