We're looking at a payback of just under eight years on ours. We have a 15kW system that's been in for four years next month. We've generated 58.41MWh in that time. Annual electricity bills run a smidgen over $200, about what it was for a month pre-solar. All heating-type things we have are propane-powered, so we really never used a lot of electricity in the first place.
Our electricity provider rolls excess generation month-to-month, so (to a point) sunny spring and fall months provide coverage for cloudy hot months. One annoying thing we didn't know up front is that they "dump the bucket" at the end of each contract year. Since our contract started in May, they dump the danged bucket right at the start of central-Texas summer. If the bucket dumped in January or something our bill would be near zero. Guess what we're going to do when our five-year contract runs out next year?
We live in an unincorporated area. The power companies serving our area didn't offer net metering (where one kW of power fed to the grid pays for one kW drawn from the grid) until the month before we ordered our system. We'd talked to the solar people several times before that; the payback without net metering was around 22 years.
We have solar power and I drive a Chevy Volt most of the time. That means my 34-mile round trip to work is made 1) without burning a drop of gasoline and 2) without paying a penny to charge the Volt most days when I get home. (Except for when I drive my Suburban, that is.) I'm by far the most conservative member of my group at work. I just sit and keep my mouth shut so I don't stir up the others. Everyone else in my group lives many miles from work, drives a gas guzzler of some sort (except for the one gal who drives a Prius), and lives in a huge house, most with pools. They gave me grief when I got my first Volt, and then accused me of "going green" when we got the solar system. My response? "Y'all do a good job of talking the talk, expecting everyone else to change their ways to fit your demands while you do nothing. What I do saves me money - all the 'green' stuff is a side benefit that I don't care about. Plus, what are the first two syllables of 'conservative'? Try walking the walk before you give someone else grief."
Yeah, I'm not particularly popular at work.
Glen