No catch, but we can give you an explanation of how we can offer this great deal:

As part of the American Recovery and Reinvest Act (a.k.a. the Stimulus Package) the government extended its tax credit on renewable energy systems.  When you lease a system, about 1/3 of the cost is covered by Uncle Sam, with state governments kicking in another 10-30%.  So, we get paid by the incentives in addition to your lease payments, you get low cost energy, and the world gets a cleaner future.  Everyone wins - no catches.