May I borrow your roof to generate electricity?

Sell the electricity, not the equipment:

Instead of making you spring for $25,000 or more in gear, Citizenrē says it will loan you a complete rooftop solar power system, install it for free and sell you back the power it generates at a fixed rate below what your utility charges. The company hopes to make back its investment with those monthly payments, augmented by federal tax credits and rebates.

While it could well be that this company doesn't make it, this is likely the way of the future for so-called "alternative energy" production since upfront costs are difficult to justify for most people and businesses.