A few wintertime utility bill stats

Here is our spending* for the last month (mid Dec to mid Jan) in our almost passivhaus here in Massachusetts:

$25: hot water (it’s probably a little less than that because my home office is on the same circuit)
$138: heating (mini split heat pump)
$6.50: HRV (fresh air)

OK, so if we have 4-5 months as cold as the middle of winter (this past month)**, that would be ~$600 for heating for a year. This compares very favorably with a recent newly constructed house we lived in which we probably paid $2000/year or so to heat AND we were freezing our tail off at that price. To stay as comfortable as we are in this almost passivhaus, I can only assume our bills would have been $500 or $1000 higher. And this house probably has more usable space. So we pay probably at least 5 times less in heating bills. Just a guess. We’ll see what the numbers are.

And for hot water for a year that’s $300/year. (And we should probably be net-zero for the year, so that is 100% solar hot water, net.) So as I’ve mentioned in a previous post, that is much better than a typical thermal solar hot water system which is often more like 50-60% solar fraction for the same price. (Solar Today reference coming) We’ll see how we’re doing after a full year! (We moved in in June, so it’s only been 7.5 months so far.) But see***

*Assuming $0.20/KWh (which is actually high compared to our current utilities actual rates, but is probably about what it costs for “green” electricity — this is what we paid at National Grid for “GreenUp” — 100% from wind and small hydro

**One could also estimate a year of heat based on the number of HDD we had during the last 30 days vs the total estimated for a year. And that would give you your multiplier, instead of my guess of 4.5. Using degreedays.net for example. And use base 68F to be fair, unless you really do keep your house at 65F!

***I think one flaw in my reasoning is that it might not cost so much for a traditional system if one upsizes the system so you can get to nearly 100% and I bet the heat pump will not last as long as the 50 years I’ve heard reported for flat plate collectors (reference coming soon). Who knows. You can’t beat my system for simplicity!


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