From 1 gigawatt to 2 gigawatts in a single yearIt took the residents of California about 30 years to reach 1,000MW of rooftop solar. And during 2013, that number doubled to just over 2,000MW. The previous record for rooftop solar was in 2012 with 500MW. Let that sink in: In a single year, as much rooftop solar was installed as during the previous 30 combined. If that's not a good sign for clean energy, I don't know what is.
While California is the leader for solar power in the US, other states are also doing well. Bloomberg recently reported: "About 200,000 U.S. homes and businesses added rooftop solar in the past two years alone – about 3 gigawatts of power and enough to replace four or five conventionally-sized coal plants."
"If California continues to grow its rooftop solar market at its 2013 pace, the state may very well top 5,000 MW in 2014 - far exceeding the goals of the Million Solar Roofs Initiative, which aimed to install 3,000 MW of rooftop solar by the end of 2016," writes Bernadette Del Chiaro in Solar Industry Magazine.
The data also shows that residential solar is mostly a middle-class phenomenon (not just a thing for wealthy people).
This isn't too surprising when you know what the price per watt of solar power has been doing in the past few decades: