Existing grid-supplied electricity is becoming more expensive. Electricity from solar panels is getting cheaper. Here's an animated map of North America that shows when the rising-grid-cost and falling-solar-cost curves will intersect for different metropolitan areas.
We used the following assumptions in the construction of this animated map:
The cost of solar in 2011 is $4.00 per Watt installed.
Grid electricity price is the average residential retail rate reported by PVWatts for the core city of the metropolitan area.
The cost of solar decreases by 7% per year.
The grid electricity price increases by 2% per year.
According to John Farrell who created the animated map, San Diego will be the first solar grid parity city, in 2013.