It's all about the flow ...

The solar panels are permanently connected to the grid and can feed power in if there's a surplus. Investor-owned utility companies buy back power at retail rates in California eventually paying for the cost of the solar system

What's the payback time?

Due to great sunshine energy available, Solar Tax Rebate and the high kWh costs in California, the payback period is under 6 years for most locations.

As a general rule the average Californinan home requires between 25 to solar panels rated at 300 watts to serve all of it's energy needs.