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Leonard Home

October 1 @ 12:00 am - 11:59 pm - January 15, 2023 @ 12:00 am - 11:59 pm

Our home was built in 1780 in the middle of hostilities between the English and colonials. Originally heated by firewood and not anything close to an airtight house, we had it air sealed and insulated. We highly recommend Jason Taylor of Carbon Cutters in Cambridge, MA. He made extensive use of blower door testing to determine where the air losses were coming from as well as extensive viewing and mapping out of the house with an infrared viewer. In old post and beam homes, there are diagonal braces throughout the structure. Without infrared monitoring during our blown-in cellulose process, we would have had a fair amount of insulation voids. The vast majority of insulation companies will probably not be doing this procedure for old houses. From a rough guesstimate of 4-5,000 Cubic Feet per Minute (at 50 pascals depressurization) when we did our first go-round of sealing and insulating, we got it down to 1,818 CFM (.5 air changes/hour) by the time Jason was through. That would be classified as a moderately leaky house—a little better than halfway between a leaky house at above 3,000 CFM and a tight house below 1,200 CFM.

Our house was the first in our historic district to be approved for solar panels. There was a bit of reluctance by some of the Historic District Commission to establish precedent for solar panels over 10 years back. Foliage largely screening the particular roof from street view and the lack of opposition by our neighbors proved essential.

We have two rooftop solar arrays, 16 panels installed in 2011 facing south on the garage roof and 26 more in 2021 on the east and west roof slopes over the rooms connecting the house and garage. The panels help power our home and plug-in Chevy Volt.

The 2011 array was paid off in eight years with a large amount of help from Massachusetts Solar Renewable Energy Credits (SRECs), version 1. The cost of solar panels has gone down over half for us from $7.74/Watt in 2011 to $3.40/Watt in 2021. Unfortunately, State support has dropped off and it is expected to take almost twice as long to pay off the new panels (if assuming minimal energy inflation). Hingham Municipal Light Plant currently offers a $5,000 maximum rebate on solar panels, up from an original $3,000 maximum in 2011. HMLP was kind enough to give several customers who filed with the State in spring 2021, in addition to the normal Town utility rebate, the amount of a State rebate that the State had run out of money to pay.

In 2011, we installed a 3.68 kW system with SunPower panels with an SMA central inverter.
In October 2021, we installed a 9.49 kW system with LG panels with Enphase microinverters.
We have an aggregate installation of 13.17 kW with a predicted annual output of 13,980 kWh.

7,290 kWh annual electrical usage (including the 80% of 2018 Chevy Volt power that is electric)
9,446 kWh (equivalent of the 682 gal. average annual heating oil usage)*
424 kWh (equivalent to 20% of Chevy Volt fuel that is 41 gal. of gasoline)
549 kWh (equivalent to average workshop propane usage of 60 gal.)
800 kWh (equivalent to average GMC pickup truck usage of 164 gal.)
18,509 kWh Total

We produce the equivalent of 75.5% of our combined house AND CAR usage energy.

We produce the equivalent of 89.7% of our house usage (not including car energy usage).

*Assuming 1 gal. heating oil = 138,500 BTUs and 1 kWh = 10,000 BTUs

Photo Tour


October 1
January 15, 2023
Event Category:
Event Tags:


John Leonard


Sustainable Features
Electric Vehicle(s), Electric Vehicle Charging, Energy Efficiency Upgrades, Energy Monitoring, Solar PV - Rooftop
System Size (in kW):
13.17 kW
Solar Site Type


Leonard Home
600 Main Street
Hingham, MA 02043 United States
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