Germany installed September 980 megawatts of solar photovoltaics in September, up from 329 megawatts in August. That brings Germany's total PV installations to 6.22 gigawatts in 2012 so far.

This data comes from The German Federal Network Agency, The Bundesnetzagentur (or BNetzA).

According to Germany Energy Blog reporting on Germany's Renewable Energy Sources Act (EEG), the optimum annual PV deployment in Germany is between 2.5 gigawatts and 3.5 gigawatts. Exceeding that range results in a decrease in feed-in tariffs for new installations by 2.5 percent per month.

Germany has more than 30 gigawatts of cumulative installed solar. A recent GTM Stat of-the-Day showed that Germany installs PV on solar rooftops ten times faster than the U.S. (Compare this to U.S. totals from the recently released U.S. Solar Market Insight totals from GTM Research.)

Solar installations in the U.S. will total 3.2 gigawatts in 2012. That's a healthy 71 percent growth rate. "But the next couple of years are hard to call," according to Shayle Kann, VP of Research.

"We have a more sober assessment of 2013," said Kann, who sees close to 4 gigawatts in the coming year, but like everyone in the solar industry, is waiting to see the impact of the ITC grant sunset. The upside is that "it's hard to imagine a down year for 2013."