Los Angeles County in April released its SolarMap of rooftops in the county for solar potential.
LA County Solar Map
So what, it's been done before, right? Not like this it hasn't. LA County used , LIDAR, Light Detection and Ranging, laser technology to map the every rooftop in LA county. What the LIDAR does is essentially do a elevation mapping, but it is highly accurate. It would probably be able to detect a soda can on the ground.
And when I say map I mean they really mapped it - Height, slope, direction, whether there is a chimney, an AC installation, etc. This is not an abstraction of the roof, this is a map of the roof itself. Every single roof in LA County (well everyone up to the date they gathered the data).
They combined the highly detailed rooftop information with ESRI Solar Radiation model and working with 8 processor servers for 30 days produced a website that allows you to put in your address and using Google Virtual earth it can tell you how much rooftop you have that is usable for Solar PV, how much you would save in electric costs, and how much CO2 you would save from being emitted. It also provides links to solar developers, cost calculators and information about incentives.
Here is the estimate for the Playboy Mansion. Not too hot, probably because it does not have much in the way of a south facing rooftop.
This is not your Granddaddy's solar potential mapping, this is the state of the art, extremely high-tech stuff.
Los Angeles is considering releasing the system, not the LIDAR itself, but the processing and other computational software and systems, as they have gotten a lot of inquiry from other cities and counties. LA County is a large owner and develper of buildings so it is a somewhat natural thing for them to do.
Oh and by the way, the cost? Well I don't have a direct cite, but my understanding is that it cost $90,000 to develop. Not a lot if you ask me.
Rooftop solar is not a panacea, it can be expensive, doesn't work well everywhere or on every rooftop (as the example above shows), and is intermittent. But it is clean, generally is available when energy is most needed, and reduces the need for new expensive, environementally dubiuos, new transmission.
UPDATE
If I can figure out a way to host this document I will. But for now I will just post this as a picture. It is unreadable I realize, so I may repost tomorrow with this document broken up, unless soemone can tell me how to host it somewhere.