Today the Washington Post had an article on electric heat pumps displacing oil and propane in Maine. Not only do modern heat pumps work reasonably well in that cold climate, but they were reported to save a lot of money, compared to oil or propane furnaces.
I had a hard time believing that they were big money-savers, as electricity rates in New England are pretty high. So I decided to check the math, using reasonably current prices and some reasonable guesses for technical performance of each type of heating.
The answer is yes. If you replace on old, inefficient oil stove with a heat pump, you should expect to cut your heating bill in half. Probably more interestingly, not even a modern high-efficiency oil furnace can compete with a heat pump, at Maine’s prices.
But I note one fact that makes Maine’s situation different from that of Virginia, where I live. I don’t think you can get natural gas most place in Maine. It would be slightly cheaper to heat with natural gas, at national average prices, if you used a 95% efficient natural gas furnace. In Maine. Given Maine’s high electricity prices.
As a final footnote, near as I can tell, the interesting thing about these new generation heat pumps is that they will work in extreme cold. Near as I can tell, they are not hugely more efficient that the prior generation, as long as temperatures are moderate.
But what about electricity versus natural gas, in Virginia?
Source: Clipart Library.com
My home heating system was designed by the internally-renowned HVAC engineer Rube Goldberg. The original 1950s gas-fired hot water baseboard heat is now the secondary heating system. That’s run by a 95%-efficient gas furnace, which also provides domestic hot water. Layered over that is the new primary heat source, consisting of two elderly ground-source heat pumps, fed by just over a mile of plastic pipe buried in the back yard.
I have pipes, wires, and ducts running every which-away. In the house, throughout the yard. In the attic. Under the slab. Up the outside of the house and over the roof (no joke).
It works. Except when it doesn’t. As was the case this week, when the super-efficient gas hot water heater failed. That finally got fixed today. Which is what got me thinking about this.
From the standpoint of carbon footprint, after I put that high-efficiency gas furnace in ten years ago, I was more-or-less indifferent between electricity and natural gas as the fuel source. Pretty much the same C02 per unit of heat, either way.
But as the Virginia grid has more than halved its carbon footprint over the past two decades, electricity has become by far the lower-carbon option. (Underlying source of data for both graphs is the U.S. EIA).
Every once in a while I revisit the issue of cost, mostly because natural gas prices fluctuate all over the place. Using the same framework as above, here’s the current match-up between my ground source heat pumps (with assumed coefficient of performance of 3.3), and my 95% efficient gas furnace.
Turns out, at current prices, and with my setup, electricity now beats the pants off natural gas, cost-wise. Not hugely different from the situation for oil in Maine. I didn’t expect that, and I’m pretty sure that’s a consequence of currently high natural gas prices.
In any case, it’s nice when you can do well by by your bank balance by doing right by the environment.
My only real takeaway is that I should minimize my use of gas-fired secondary heating, within reason. I figure if the citizens of Maine can get by with nothing but heat pumps, I should be able to do that as well, in the much milder climate of Virginia.
