We installed an 11kw array on the barn roof, which covers 30-50% of our electricity needs depending on the time of year. The leasing option came to about $180 a month after state subsidy. That covers the panels, the installation, the inverters, new meter, everything.
Now, a lot of people will complain that the leasing option is total BS, its a bad idea, etc etc. the deal through this particular company is that you enter into a contract for 15 years at a set price (in this case, the $180 per month). At the end of 15 years, you can either return it back to the company, or extend the lease at the same price for an additional 5 years. At that point, you have the option of either returning the panels back to the company or buy them outright for fair market price. The idea is that in 20 years from now, solar panels manufactured today are going to basically be worth dirt, so the buy-out option should theoretically be super cheap.
Out of the box, we saw about a $15-20 savings on the bill, so off the bat (i.e. we pay $180/month to lease the panels and they create a net $200 worth of energy), so we're not really saving a huge amount right away. However, as things tend to, electricity costs (along with most other forms of conventional energy) will most likely increase, so the margin between the price of that same amount of energy will increase while the lease stays the same price.
You can see some pics of the installation and finished product here:
http://www.aquariacentral.com/forums/showthread.php?t=202133