A solar system is installed every 4 minutes in the US and every 2 in Japan.

GreentechSolar: “The U.S. is now installing one solar photovoltaic (PV) system every four minutes as well. If market growth continues at its current pace, the American solar industry could be installing a system every minute and twenty seconds by 2016.” “….It may not quite match Big Mac sales yet, but solar is on an extraordinarily fast growth trajectory. According to figures from GTM Research, two-thirds of all distributed solar in the U.S. has been installed over the last 2 1/2 years. And by 2016, cumulative installations of distributed PV will double.
That means the U.S. will hit 1 million cumulative residential solar installations by then — making the market in 2016 ten times larger than it was in 2010.
Japan data