While we planned on putting PV on the house all along, we delayed installation since, like most people, we'd already spend much more than we had hoped for on the house, and PV is expensive.  We were originally thinking in  terms of a 1kw system, but based on our electric usage we found that even a 3kw system wouldn't supply our yearly electric need (only about 50-60% of it).  At $6k/kw (2005), PV isn't cheap, but given that the state of Washington was offering a 10 year production rebate and we now felt we could afford it, we opted for the 3kw system, which is all that fits easily on our roof anyhow.  In addition, I borrowed a watt meter and began trying to figure out ways to use less electric.

Since we'd already run a wire from the basement electrical panel to the attic, installing the PV was straightforward:  they show up, drill a few holes, run some wires, and then lug all the panels and mounting up on the roof and two days later you've got solar electric.   Since we installed in July, I'd like to say my meter ran backwards the next day, but alas, you have to fill out some paperwork and pay an application fee, and then a few weeks later the utility comes and gives you a meter that runs backwards.

To see how this system has worked, click here.

A note on incentives:  Its never clear to me that the various incentive programs out there ever make much sense in the long run.  We clearly need to make PV more affordable and we clearly need to install it as fast as possible, but how to make the economics work just isn't clear to me.  The biggest problem with incentive programs is that they can go away at any time, making it a hard economic decision to invest in R&D when the economic only works out if the rebate exists.