In the U.S., solar photovoltaic (PV) panels are, somewhat unexpectedly, suddenly the belle of the renewable energy ball — and their dance card is wide open. There is now more solar PV capacity planned for the immediate future than any other renewable you can name. Wind, solar thermal, geothermal — it's like they all showed up at prom in powder-blue tuxes and Trump hair, and now they can't get a date with an investor.
More than four gigawatts of solar PV are "in development" as of the end of 2010, which is almost as much as the entire sun-baked country of Saudi Arabia has planned between now and 2020. Not all of that will be realized, of course, mostly because solar PV is still an immature industry on the construction side, full of small-time players, unlike wind.
Regardless, it's good news, because it means solar panels aren't just for hippies and hobbyists anymore:
Although these figures are somewhat limited, they do highlight the underlying story: Given the incredible cost and price reductions seen in solar over the last few years (50 percent price declines in modules since 2008, 20 percent decline in installed price in 2010 alone), solar PV is on a path to large-scale adoption, similar to where wind has gone over the last decade.
NREL reports high growth in U.S. solar PV, Climate Progress.