From 2008 to 2014 Solar PV Capacity grew 10 fold

Although solar energy only contributes a small portion of all forms of renewable power source(about 10%), it has been the fastest growing one.

One of the main reasons behind this is that since 2009 the price of solar panel has dropped sharply (about 70%)

As you can see in the following chart the negative correlation between price’s fall and installations growth was very obvious. (in the U.S)

National Geographic: Solar Energy Sees Eye-Popping Price Drops