Tool to calculate benefit of rooftop solar in Cambridge, Mass

Gmoke sez, "The city of Cambridge, Mass has teamed up with MIT to produce a Solar Tool that allows people to type an address into a website and get a detailed account of that roof's solar electric potential. This is probably the most detailed service now existing and every building in Cambridge is covered. You can learn how much of your roof sees enough sun for a PV installation, how large that PV installation can be, how much it will cost, how high your Federal and state tax rebate will be, how much electricity it will produce in a year, and how much carbon it will displace."

Solar Tool v.2 (Thanks, Gmoke!)


  1. The city of Cambridge, Mass has teamed up with MIT to produce a Solar Tool that allows people to type an address into a website and get a detailed account of that roof’s solar electric potential.

    Ha ha!

    1. The Cambridge Solar Tool seems to have a higher level of detail, does not require you to login, and is not connected to any single provider.

  2. I notice the map appears to be loading a second set of orthophotography over the default Google Maps imagery for some areas, and was curious, why? The default imagery for this area seems to be summer time (leaves on trees), and the added overlay is in the winter (no leaves on deciduous trees). Does it take the differential into account, and consider which roofs might be shaded in the summer but clear in the winter? I thought that might be the reasoning, but the site says they get foliage data from LiDAR (perhaps using multiple returns?), not image classification, so I’m not really sure what role the second imagery set plays. Just using it for the greater resolution?

    Posting here in case the devs happen to notice they got Boing’d.

    1. Hi Jason,

      The orthophoto imagery is used because the default Google maps imagery is not orthographic, but has some perspective shift. This makes the visualization of the data not match up with the rooftops of buildings unless an orthophoto is used.


    2. Some of the people at MIT who developed this program previously developed a daylight and shading tool, DaySim, at Harvard.  I suspect that they used that tool to generate the annual shading patterns from trees and other roofs but I could be wrong.

    1. London and Singapore are interested in doing the same kind of thing and are talking with the folks at MIT now.

    1. In Cambridge, everything is centered on Harvard first. 

      Christoph Reinhart used to be at Harvard but switched over to MIT.  Maybe it’s a holdover from his Crimson days.

  3. Whenever I look out an airplane window on landing approach and see all those south-facing roofs of suburbia I see a resource for our energy future. Even at current per-watt prices for photovoltaics, it’s an economic option for cutting peak demand in air-conditioning-dependent cities, if only legal and utility policy obstacles were removed. Instead we build centralized solar stations in deserts miles from consumers, which defeats one of solar’s strongest assets.
    Without a national effort to reduce cost of photovoltaics, I suppose we’ll have to wait for China to produce solar cells that cost no more than conventional roofing material.

  4. Does it calculate how hard it will be, how long it will take and what it will cost to convince the local planning authority, the architectural heritage review board, the council and all the NIMBYs to let you have these solar panels?

    1. DOE is streamlining solar permitting and inspection procedure in the US on a national basis with a program called Solar 3.0 that they have just started to roll out.  Germany is far ahead on this process.  There will always be problems with NIMBY and with solar rights disputes but we can start the process anyway.

  5. Cool! I see that my roof is one of the least PV-friendly of all the roofs around it, yet it still would pay for itself in 6 years and represent a 17% ROI. Tempting!

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