A snapshot of John Farrell's animated map of the years in which solar energy will be cheaper than grid electricity in major American cities. Farrell predicts that San Diego will be the first city to reach solar parity, in 2013. How he did the math:
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.
(Hat tip: Mark Frauenfelder)
The Dish 