I recently replaced a (very) old gas boiler with a new gas boiler after trying and failing to make an air-to-water heat pump make economic sense. (It 100% would have worked technically/thermodynamically.)
It was going to be a bit over $20K more, which at only 4% opportunity cost of that money (low, IMO), means that an $800 savings per year would literally never pay back, let alone within a 20-year projected service life. I’ll re-evaluate 15-20 years from now when it’s time to change again. (Eastern MA)
Our grid is plurality natural gas fired, so I’d expect them to broadly track for the majority of the lifecycle of this equipment.
A slate roof precludes advisable/economic solar installation, plus the major part of heating load is in winter (obviously) and in the 75% of the day that’s not 9AM to 3PM.
As a fellow owner of a slate roof I recently came across panels made to look like blocks of slate tile[0]. They look to be a bit less efficient than a traditional panel and I've not looked into the costs yet but it's nice to have the option! I imagine there would be similar products in your neck of the woods.
Those are beautiful; thanks for the reference! At the price of labor in New England, I kind of doubt those will have an economic payback either, but I'll do a little more poking around.
I researched and shopped it pretty hard (the latter to limited effect). Lots of companies do boiler swaps in ~3 hours with one plumber or one plumber and an apprentice/laborer. Only one company would even quote the air-to-water (which has its own dangers now and for 20 years of operation).
Changing from gas to air-to-water heat pump involves electrical work (inside and out), core drilling through structural brick walls, some landscaping work, much more plumbing work (both water and refrigeration), and more and more expensive equipment (way more piping, a buffer tank, a domestic water storage tank, and the indoor and outdoor units), plus the labor to install, inspect, and maintain all that.
Heating load on design day was calculated 78KBTU/hr. (Old boiler was ~60% efficient, 200KBTU/hr input and cycled easily on design days.) I think the true figure is likely just a bit less, but the exact figure turns out to be irrelevant for a gas combi boiler as it’s already sized large enough for the higher domestic water heating load. For a heat pump, sizing to load and using storage tanks is critical.
I really wanted to have the switch make sense. It wasn’t even close, even with several thousand in additional incentives.
Wow. An enormous cost indeed. I think you made the right choice, at least for now.
When climate becomes enough of a problem that governments start taxing fossil fuel instead of subsidizing it, the story may be different. But for now I would have made the same choice.
Yeah, I'm consoling myself that we're at least using 34% (Dec, 1°F colder this year) to 56% (Nov, 1°F warmer this year) less gas than same month last year, so we at least reduced our consumption significantly, even though it practically locks us into local burning fossil fuels for a couple decades.
The old boiler really was a disaster from an efficiency standpoint. 1950s General Motors (not a typo) oil burner, converted to gas with a single-stage [200K or 0 BTU/hr] burner, drawing combustion air from the basement, and sending 160°F-190°F water to the building and taking up an enormous footprint in the basement. Now has a 95% Bosch combi, drawing combustion air from the outside, using outdoor reset to send 118-136°F water to the building, and hangs on the wall taking up about as much space as two milk crates stack atop each other.
Our grid is ~40% natural gas anyway, so when taxes hit natural gas, they're going to hit heat pump users as well.
That's an interesting calculation you have there. We wouldn't want something bad to happen to it. My associates and I offer coverage against unanticipated rises in gas prices. We call this prote^h^h^h^h^h insurance.
More seriously, I can see how this might make sense in the US, assuming that US domestic gas production and politicians can keep the fossil fuels flowing, but the calculations have much wider error bars where I live. For me, US$20k over 20 years is a lot of nights not tossing in my sleep while I dream uneasily of tomorrow's headlines.
That's an interesting amount, since I assumed things are cheaper in the US. I live in Finland and we got an offer for my house to install an air-to-water heat pump system (with an existing radiator network, which I assume you have too with your old gas boiler) for 13 k€ total. Is your house very big or what explains the huge difference, since you quote it would have been $20k more than some lower price?
Not massive. ~2650sq ft, 2 levels plus a finished attic. 1920s structural brick (so limited and varied cavity, but good attic and roof insulation).
Boiler swap were $15-20K bids minus $1.2K in incentives. A2W was $42.4K minus $7.5K in rebates (with some uncertainty as to rebate payout, because they could require additional weatherization as a condition of the heat pump rebate, which wouldn’t be known until after project commencement).
I think the difference is we have one company in that market and they can do 6-8 boiler swaps for the same amount of bidding and installation labor involved in one A2W job, plus that gets them 6-8 customers on maintenance plans instead of just 1. I have a sibling comment laying out some of the (genuinely) more work it would take to switch to a heat pump: https://news.ycombinator.com/item?id=34352854. It was going to be "2.5 to 3.5 days" for the plumbing crew, a half-day of electrical, 4 person-days of trade helpers (landscaping and rough framing), outsourced masonry labor for the coring, and multiple inspections. That's a lot of mouths for my job to feed for them to get just one customer (and around $10K in equipment markup to cover overhead).
I don't blame them for bidding it a lot higher than a job that takes just a plumber and an apprentice 2.5-4 hours with no outsourced labor and only one inspection in order to get one customer (and around $5K in equipment markup to cover overhead).
My new (return air) heat pump that heats my whole house and provides all hot water is $6k. I expect a 15 year life. The only thing that could possibly be cheaper long term would be drilling a hole for ground heat, which would be around $15k with a similar pump and the difference being the whole.
The pump heats water and circulates it in the floors of the ground floor of the house and in radiators on the top floor. It also has an internal hot water tank for tap water, and a backup electrical heater.
I do have ducts for exhaust air from kitchen and bathrooms. That’s where the pump takes it’s heat from so it doesn’t need to work with outdoor temp air.
It was going to be a bit over $20K more, which at only 4% opportunity cost of that money (low, IMO), means that an $800 savings per year would literally never pay back, let alone within a 20-year projected service life. I’ll re-evaluate 15-20 years from now when it’s time to change again. (Eastern MA)
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