Others have already made this point[1] but to me, SolarCity has some aspects that make it look like more of a of a tax-arbitrage business than a solar panel retail business. It reminds me a bit of the ethanol blending tax credit, which led, in some cases, to companies mixing ethanol with petrochemicals solely for the tax benefit.
[1] http://www.newsmax.com/BradleyBlakeman/solar-kroll-subsidy/2...