Growing concern about climate change and rising prices of fossil fuels has prompted governments to stimulate the development of renewables. The most common instrument is a feed-in tariff (FIT). This paper empirically tests whether or not FIT policies have been effective in encouraging the development of photovoltaic solar (PV), explicitly taking into account the structure and consistency of FITs. Panel data estimations are employed for 30 OECD member countries in the period 1990-2011. We find a positive effect of the presence of a FIT on the development of a country's added yearly capacity of PV per capita. This is in line with the results found in the existing literature. However, our study shows that the literature underestimates the potential impact of FITs, as the effect of a well-designed FIT is much larger than the average effect of the currently applied FITs. Not only the height of the tariff is important, but also the duration of the contract and the absence/presence of a cap have an impact. We also show that consistency greatly affects the effectiveness of FITs. Consistency is especially important when the tariff of a FIT is low. The total effect of a FIT can be seven times larger if it is well designed. Our results are robust for differences between countries with respect to the availability of other policy instruments, the use of nuclear or hydro power and the level of CO2 emissions.