Not necessarily, it could very well be a PR trick. Going solar is trendy so they may have done it to get some press.
It pays off but maybe in extra iPhone sales /brand building
My point was not to assume that this makes sense economically just because Apple did it. They have other ways of getting their money back and if they lose, it's just a rounding error http://finance.yahoo.com/q/cf?s=AAPL&annual
You sure have seen the Beyond Petroleum ads, haven't you? http://www.environmentalleader.com/2008/01/15/beyond-petrole...