comforted banks in risk mitigation. The relative success of this policy in various European markets (Germany, France, Italy, and Spain) can be largely explained by the extent to which governments have succeeded in meeting two key conditions, that is, by explicitly linking FiTs policies to well-defined and binding targets that are part of a broader energy and climate policy and by providing investors with a high degree of transparency (easy to navigate through the structure), of longevity (creating a stable and durable environment), and of certainty (providing measurable and sufficient revenues to support a reasonable rate of return).

Germany firstly (1990) adopted a "law on feeding electricity into the grid" \[[@B56]\], requiring a guaranteed purchase of utilities from renewable energy sources at prices that were determined as a percentageDriven by the policy, solar PV in Germany has resulted in a drop of peak electricity prices by up to 40% with savings between 520 million and 840 million € for consumers \[[@B45]\]. At the same time, the surcharge paid by electricity consumers has increased, reaching an overall cost for consumers of 20,000 million € in 2013 \[[@B54]\].

The Spanish feed-in legislation was set by Royal decree 1578/2008. For photovoltaic installations, the decree categorized two installations, that is, building-integrated installations and nonintegrated installations, with different power scales with differentiated Tariffs. In 2010, the Spanish government has retroactively reduced the Tariffs paid to renewable generators. However, given a series of factors, and the unsustainable cost of the FiT mechanism, the Spanish government (27/01/2012) temporarily stopped accepting new FiT applications for