An update from the Medford DER that is a part of the Thousand Homes Challenge.

Here’s what a 6.9kw solar array can do to your electric bill:

In the span of 2 months, we’ve gone from consumers to producers of electricity back to the power grid, with all of our home’s electricity demands met !

The solar PV system on the roof is leased from Community Energy and installed by Transformations Solar of Townsend, MA.

This, combined with the ultra low heating demands of this super-insulated home is a major triumph for proving the efficacy of retrofitting an old home. This 1908 2-family now outperforms “code built” new-construction homes by a wide margin!

More to come, as we continue tracking our Thousand Homes Challenge compliance over the next 10 months.


4 thoughts on “Solar PV ROI

    • Hi Mark, thanks for sharing this calculator. Does a nice job. As far as ROI goes, this was a leased system, and has basically cancelled out me electric bill. The array is significantly large enough, that the monthly lease payment is covered by the excess generation from the array. So for zero money down, I’ve made my electric bill go away…!

  1. Hi Dennis, While there is a Nest thermostat installed on the radiant heat loop, the setback functions are mostly unneeded, as the envelope has a hard time losing even one degree of temperature in a 24 hour cycle in the dead of winter… As for lighting automation, that was not installed, other than motion detectors on outside security lighting. I would agree that some further incremental reductions in consumption may be possible with interior lighting automation, but the installed cost and complexity seemed a bit hard to justify for 2 1500SF condos…

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