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I have a gas heater for my 3,100 sqf house in the PNW, where winter temperatures tend to be around 30s-40s from December to February. I looked at my recent gas bills and am noticing pretty high utilization -- ~185 "Therms" (whatever that is -- this is the unit I'm billed for) between mid November to mid December, which cost around $250 with taxes and fees.

I suspect there are issues with insulation because 1) it's an older (1993) built home, and 2) I feel some slight cold drafts in certain areas of the house. To be clear, all the "obvious" stuff is there -- my exterior walls are insulated, doors and windows have weatherproofing, etc.. but I suspect one or more of these have failed and may need to be repaired. Also I have fireplaces surrounded by brick veneers that have some cold drafts nearby. So I don't expect many "easy wins" here, though I do think there are improvements that can be made.

I'm now wondering though: in terms of time and money, would I be better off spending a few weeks finding and eliminating all sources of heat loss in the house, or just replacing my heat unit with a heat pump?

I realize it's not an apples-to-apples comparison, and I'd still have the heat loss / energy waste problems even if I go the heat pump route without fixing the insulation. But assuming no easy / obvious wins in terms of insulation, is the heat pump route a better use of my time?

(Note: I can try to DIY the heat pump installation)

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    Air sealing is almost always the cheapest/easiest path with high value. I can tell you from my PNW experience that split and mini split heat pumps are both great here, given our mild winters. Don't expect a reasonable payback period though unless your existing unit is 80%.
    – KMJ
    Jan 2 at 18:30
  • FYI, insulation practices were fairly modern in 1993. You should have fiberglass batts in the walls and vapor barrier to the interior. That shouldn't be a concern. However, house wrap and other air sealing wasn't well established yet. That's where I would put my attention.
    – isherwood
    Jan 2 at 19:21
  • Thanks for the feedback! A few clarifications: 1) The siding was completely replaced in 2020, including new house wrap. 2) The insulation itself seems to be in good order from the places where I drilled through to do work (and later repaired). 3) I believe the gas heater is the original from 1993. 4) Attic is very well insulated to the point of being very stuffy. This is why I was unsure if there are many easy wins remaining on the insulation or sealing side of things, and why I started considering heat pumps. I'll ask a separate question if I decide to DIY that.
    – peter
    Jan 2 at 20:50
  • A therm is 100,000 British Thermal Units, (BTUs) and a BTU is enough heat energy to heat 1 lb of water 1 °F It's roughly equivalent to 29 kilowatt hours. Natural gas has varying energy content, so the meter records volume and the gas company calcuates how that relates to therms depending on what the gas they were putting into their end of the pipe had for energy/unit volume that month.
    – Ecnerwal
    Jan 2 at 22:28
  • What's your price per kWh for electricity? Compared to resistance heat, your gas seems to be ~5 cents kWh. Compared to a heat pump, particularly with that mild temperature range, the gas is about 15-20 cents/ kwh. So if electricity costs 15-20 cents they are currently about the same in your area, and if electricity costs 10 cents the heat pump will cost less to run, and if it costs 25 cents the heat pump will cost more to run.
    – Ecnerwal
    Jan 3 at 0:36

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Fixing insulation and infiltration (e.g., caulking and house wrap) should be first priority, whether burning gas or using electricity in a heat pump. Many public utilities provide free inspection of insulation; some use thermal IR cameras to show where the heat leaks out. Some also will perform repairs and other fixes, or provide materials, or low-rate loans for repairs.

Check your local gas supplier, and even the electric utility (though you use gas, you can justify use of the electric utility's inspection by mentioning a possible switch to heat pump).

Switching to heat pump in a poorly insulated home might cost more in electricity than the current gas bill.

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