Despite being a vintage home that did not allow for adding wall or basement insulation, and without changing any windows, this house’s bills and carbon emissions were both cut in half.
The house is in Arlington, MA with 5,600 heating degree days.
The program consisted of:
- Insulation was added in the attic, some air sealing was done in the attic (but neither insulation nor air sealing was done in the basement),
- Air sourced heat pumps were added
- A fairly small solar array was added to the roof (which has considerable shade from nearby trees)
- The natural gas furnace was retained
- A wood-burning stove was added for both ambience and heating
Here are the details:
Congratulations are in order! You have cut your carbon emissions by 56% and your bills by 32%. The cut in the bills is despite the price of natural gas being 32% higher than it was when I measured your house back in 2019 and electricity having gone up 13% since 2019. Natural gas will soon have doubled in price from 2019 and electricity will soon be 50% more expensive so you have insulated yourself from those increases as well. You are also not funding Putin’s war in Ukraine.
In the year before I worked on your house your total bills were:
$2,632 for gas, $830 for electricity
In the last 12 months they were:
$1,033 for gas, $722 for electricity net of solar, $600 for wood
Your total carbon emissions before the “fab four” were 11.4 tons per year and after they were 5.8 tons, for a cut of 56%.
So I saved you $1,107 per year so that is what you owe me. This is 32% cut in your bills. And this is with the prices for both natural gas and electricity having gone up considerably since I started work on your house. If I recalculate your “before” costs at today’s prices for gas and electricity your “before” bills were $4,207, so you can think of your savings as having been more like $1,851 or a 44% cut compared to the recalculated costs before the Fab Four. So roughly roughly you can say you cut your carbon emissions in half and cut your bills in half too. I assumed you were using electricity from the grid at the average ISO NE emissions per kWh rather than the zero emissions from the “green” electricity you buy because you pay extra for that.
With the limited amount of sun available on your roof I think this is a very good outcome. You are absolutely right that it would be better for everyone if the utilities supplied more green electricity. In addition to the money savings and carbon emissions savings you have almost certainly increased the price of your adorable little house with both the heat pumps and solar panels.
Did you burn the entire cord of wood in the last 12 months? If not let me know how much you burned as I suspect I have overestimated your carbon emissions.