We hear that prices on systems will continue to go down, so waiting isn't so bad.
Waiting is bad for three reasons;
1. The 30% federal tax credit expires on Dec. 31st 2016
2. The net metering capacity will fill out sooner than that in many markets.
3. State and utility company rebates will expire or run out of funds sooner rather than later.
These are incentives for getting solar rolling. Once the costs for panels and ancillary equipment drop in cost, so will the incentives.
if we are going to subsidize solar, it should be based on an estimate of the system's annual production, rather than the system's cost.
It is, indirectly. A 5kWh sized solar generation on a home is going to produce a certain amount of electricity. If it doesn't, the recovery of the buyer's capital is going to fail to meet it's goals. Solar companies are entering into contracts with buyers that the system they design and sell will produce a set volume of power. This is required by law in California. Every contractor selling solar systems are required to use this calculator when sizing a system so that the customers know they are not being over sold on a system. I've got to say, it's pretty well regulated that you know what you are buying when you contract for a solar installation.
In my project, the calculator takes into account my latitude, 38 degrees, the azimuth, 160 degrees (20 degrees East of South) and a tilt of 22 degrees. A perfect set up at my latitude, is 180 degrees and a tilt of 26 degrees. My less than perfect mounting accounts for about a 3% loss of efficiency. The calculator says that a 5kWh sized solar plant will generate 3650kWh of electricity in one year. If it doesn't, within reason, then something is broken.
A savvy customer is going to work out the math for themselves and not take a salesman's word for it. I've worked with a few outfits, one place even has solar plants set up with on-line monitoring so you can view their production as well as past performance. Systems I've checked into all offer wifi connectivity to measure solar performance down to the individual panels. Historical data is archived and several solar product producers will host your data on their website for scientific data gathering purposes.