If you have the space, I’ve seen amorphous silicon panels (Kaneka) for less than $1/watt. They’re inefficient (6% or so), so you need a lot of room for a given amount of power. But they do better in cloudy weather than mono- or poly-crystalline cells.
A friend of mine put in a solar heater for his pool and loves it. It takes up a huge amount of space, but he has an otherwise unusable east-facing slope right next to his pool so it worked out great. He changed out the pump motor for something more efficient, and that helped keep the power consumption down.
The same friend put a 4kW system up a couple of years ago, and he had a long-running fight with the (well known) contractor over the actual vs. promised performance of the system. If you do one of these, make sure the contractor gets the engineering right and puts the design numbers in writing.
If you don’t use a lot of power, the payback for solar can be lengthy or non-existent. Don’t forget to factor in the time value of money when doing your calculations (unless you’re a serious gold bug who thinks the dollar will be worthless in a few years anyway).
Mandatory Time Of Use (TOU) metering could change solar economics, and it may be coming soon. My neighborhood is scheduled for smart meter rollout in December, but I haven’t heard anything about tariff revisions that mandate residential TOU. SDG&E has a voluntary SES TOU (“Net Electric Metering” in their jargon) program, but UCAN has serious questions about whether the program works for most people. I wouldn’t depend on it helping the consumer.
