For the first time, EIA is out with solar capacity data that includes solar systems below 1 megawatt. The results confirm several important things. First, EIA calculates total US solar capacity by the end of 2011 at least to be 3,536 megawatts. http://www.eia.gov/todayinenergy/detail.cfm?id=8510. That is a huge increase from the approximately 500 megawatts that operated as recently as 2008. The EIA data also uses Alternating Current as the unit of calculation and that produces slightly lower total number than if Direct Current was used.
EIA also estimates that the distributed solar or solar at customers' homes and businesses accounted for 2,500 megawatts of the 3,536 megawatt total. Distributed solar is especially hot and competes not against the competitive wholesale generation price but against the full electric rate that includes transmission and distribution costs that are often substantial.
While the solar boom through 2011 was significant, it is nothing compared to what is happening with solar installations in 2012. US solar capacity is likely to double again this year and exceed an extraordinary 7,000 megawatts by December 31.