The Consumers Energy bill showed up on Saturday, and before I opened it I wrote a guess on the back of the envelope: 145 therms for January. The bill said 139. I said "ha" out loud in an empty kitchen, to an envelope.
This is the comparison I've been waiting all winter to make, so here it is, with all the caveats it deserves.
The numbers, side by side
- January 2025: 178 therms, $214.
- January 2026: 139 therms, $171.
That's 39 fewer therms, about 22 percent less gas, and $43 less money. The two months before tell a similar story. November went from $98 last year to $84 this year, and December from $162 to $139. Add up November through January and we've spent $394 on gas this heating season, against $474 for the same three months last winter.
The dollars dropped a little less than the therms did, which is the first thing that makes this tricky. Divide each bill by its therms and last January cost about $1.20 per therm all in, while this January cost about $1.23. Rates and fixed charges moved a little between the two winters, so the savings in dollars come out smaller than the savings in gas. If I'd compared only the bill totals, I'd have shorted the insulation a couple of points.
It also helps to remember that not all of the bill is heat. Our summer gas bills run $38 to $42 a month, which is the water heater plus the customer charge. That chunk shows up in January too, so the part of the bill that actually heats the house fell by more than the total did.
More than one thing changed
I'd love to give all 39 therms to the insulation. I can't, because since last January we've done all of this:
- Foam board on the rim joists in early October, plus the one bay I skipped and finally filled after the cold snap on January 13th.
- The contractor's air sealing and cellulose in the top attic and knee walls, October 21st and 22nd.
- An ecobee set to 67 when we're home and 63 overnight and while we're out. The old thermostat mostly sat at one number because neither of us remembered to touch it.
- Weatherstripping, door sweeps and outlet gaskets in early November.
- A new water heater in mid-November, which also burns gas.
My guess is that the air sealing and the attic did most of the work, since the blower door number dropped 29 percent and that's a lot of leaking air to stop. But the setback schedule is pulling its weight too, and a monthly bill can't separate the two. The water heater is the same size and type as the old one, so I'm calling it a wash, though that's a guess as well.
Two Januaries are never the same January
The other reason this isn't a clean test is weather. This January had the night it hit 6 below and the kitchen pipe nearly froze. Last January was more of a steady gray cold without the extremes. I looked up heating degree days for Grand Rapids for both months, which is the measure utilities use for how much heating weather there was, and they came out within a few percent of each other. That's close enough to make me hopeful and not close enough to make me certain.
At work, comparing this January to last January would be like comparing two demand periods with different promotions running. You can do it, but you footnote everything.
The payback math, with footnotes
If February and March follow the same pattern, I'd expect this heating season to land somewhere around $140 to $160 below last winter's. The insulation should net out at $2,410 after the $750 rebate that arrived on January 9th and the federal credit we expect when we file. On gas savings alone, that's a payback of fifteen or sixteen years.
I'm fine with that, because the gas bill was never the whole reason. On a cold evening the upstairs bedroom used to run about three degrees colder than downstairs, and now it's within a degree. The ice on the eaves is a fraction of what it was. Tessa stopped sleeping in a hooded sweatshirt, which she pointed out is a benefit I can't put in a spreadsheet. I put it in the house sheet anyway, in the notes column.
