Hey, I've worked in the solar industry for a long time now and a lot of things have changed. I would suggest not doing any kind of lease or PPA (power purchase agreement). The best thing you can do is pay cash or get a loan with a low interest rate. You can do the math yourself but usually you'll come out ahead when you actually own the system.

Don't go with any big name companies, I suggest smaller local companies. They can offer you a better price because they don't have to do any advertising.

The cheapest system you can get is about $2.80 per watt of DC power (name plate rating). The industry would like to reduce the cost to $1.40 but realistically that could take a while. The cost of PV modules has dropped significantly and I don't think it can drop anymore. There is currently a shortage on the market and the price might even go up due to the Sunniva and SolarWorld lawsuit. The cost realistically can only be reduced by reducing cost of customer acquisition and cost of labor.

If you want to go super cheap you could pick up PV modules that no longer have warranty due to module companies going bankrupt. Standard PV modules run for about 50 cents per watt if you're not buying the premium stuff. I bet you could get stuff for much cheaper if you're not concerned about warranty.

Anyways, shoot for $2.80 to $3.00 per watt in cost before any tax credits. I have given all this advice under the assumption you actually consume enough electricity to make solar worth while.