[blahedo]

People are reluctant to install them because they don't work as well as the good old boilers we'd be replacing. I'm not saying they can't, and I'm not saying that there are zero models out there that work. But in practice, a lot of us that have interacted with heat pumps have the specific experience that they get anemic as the temperature goes down and eventually become unable to do much of anything.

I live in the mid-Atlantic (US) climate zone, where it's certainly not as cold as the north but definitely goes well below freezing regularly for several months of the year. The place I've lived for 15 years had a heat pump and a (oil) boiler with radiators, and when it was below 40°F (~5°C) I had to switch to the radiators. It's because it's old, everybody told me, modern heat pumps are better! So last year when both systems needed repairs at the same time, I not-entirely-willingly switched to a brand-new 2024-model heat pump. It absolutely could not keep up when the temperature was freezing until they came back and installed resistive heat strips for low temperature---these seem to be a fancy version of the heating elements in a space heater or a toaster. They do not seem to be particularly efficient. And to the extent that my "heat pump system" does now more or less keep the house adequately warm, if not as comfortable as the radiators always could, it's not solely due to the heat pump, but the other stuff they had to put in because the heat pump couldn't keep up.

My experience is far from unique. Maybe it's that they only install the good ones in farther-north locations! Maybe it's that the good ones are just way more expensive! I'm perfectly prepared to believe the factual statements about the physics and the tech. But if we're talking about perception and "why aren't more people looking to install heat pumps", it's because lots of people have experiences like the above, and that is what the industry needs to work on.

[amarant]

This is such a weird tale to hear. I heat my 2 story 147m2 house in Sweden with a single heat pump and it's downright cosy down to -10C. I have noticed that my office, which is located at the furthest possible place from the heatpump, tends to get a bit chilly when outdoors temperatures fall below -10°c. usually a blanket is enough to keep me toasty, but on the rare occasion that it gets real cold (below about -15°c), I have a fireplace to save the day. That fireplace actually gets used more for the cozyness of a fire than it does for actual need of heating, but it does help on the worst days of Scandinavian winter.

All this to say: if your pump can't handle +5°c, I wonder if you got scammed or if there are other factors at play? Is your house insulated at all? Do you keep your windows open throughout winter? Your experience is so different from mine it's hard to believe we're even talking about the same technology!

[starkparker]

It's the insulation. While it depends on the location and geography, I'd wager that American homes are probably less well insulated than Swedish homes because they didn't have to be.

That contrasts quite a bit with Swedish home standards, which have long been built more air-tight and with considerably better insulated even if they're of comparable age. This has been true for decades, became even more stark in the 1980s, and likely remains very different on the balance: https://www.aceee.org/files/proceedings/1984/data/papers/SS8...

[ip26]

Some heat pumps bottom out at 35F, some at -15F. It seems to be down to the breed of heat pump, and there isn't much in between.

[throw0101a]

> The place I've lived for 15 years had a heat pump and a (oil) boiler with radiators, and when it was below 40°F (~5°C) I had to switch to the radiators.

When was the heat pump manufactured? Mitsubishi, for one, publishes data were they have 100% heating capacity at -15C, which some models being 100% at -20C and -23C:

* https://www.mitsubishielectric.ca/en/hvac/home-owners/zuba

There's a website for cold climate air-source heat pumps (ccASHPs), that has performance data down to (at least) 5F/-15C:

* https://neep.org/heating-electrification/ccashp-specificatio...

* https://ashp.neep.org/#!/

OEMs can optionally have publish data on "Lowest Cataloged Temperature" if it's below 5F/-15C.

Also: how (air) leaky is your house? how much insulation? For a lot of folks dealing with those two things would be more cost effective than anything.

As it stands, even if you are heating with "cheap" methane (née 'natural') gas, propane, or oil, you're throwing money out the window by letting the heat out in winter. (And the heat in / cold out in the summer.)

[Merad]

I have to agree. I've spent about 2/3s my life in houses with heat pumps and the last 5 years with a gas furnace (the rest being wood heat as a child). Mostly in Western NC and Eastern TN near the mountains, so chilly but not extreme cold.

Heat pumps work, but they aren't nearly as _pleasant_. You can write essays about the efficiency of heat pumps, how lukewarm air works just fine to warm the house, how heat pumps are great _most of the time_ and you can supplement with space heaters or whatever when they fall short... But as long as furnaces are accessible and affordable, an awful lot of people are going to choose to have nice warm heat that is always going to be nice and warm regardless of the outside temperature.

[smnrchrds]

I have never had a heat pump, so I wasn't aware of this shortcoming. Could you please explain a bit more how different it is with heat pump compared to furnace?

[estimator7292]

Resistive heat strips are what all electric furnaces use. It's just a bunch of coils of nichrome heating wire. The efficiency of a resistive heater is basically 100%. One Watt of electricity in gives you one watt of heat out.

The mistake people make is assuming a heat pump can do everything by itself anywhere in any climate. If you have cold winters, you need a dedicated furnace to supplement the heat pump.

I say supplement because while an electric furnace is near 100% efficient at turning electricity into heat, a heat pump can be far more than 100% efficient. And that's the crucial detail: a heat pump can give you more heat per Watt than a resistive heater when outside temperatures are warm enough.

[lbotos]

What brand and was it sized for winter load?

Im in NY, 6 heads across 3 floors with 2 heads per outdoor unit. 2500sf covered.

Mitsubishi h2i (i think im on my phone). Get plenty warm in the winter as my sole heat source. I could have gotten smaller outdoor units and had resistive backup but I didn’t want that.

[prlambert]

Yes this is actually the worst – when open minded people get a heat pump for "the right reasons" and then have buyer's remorse. Completely backfires the transition. Do you have a ducted or ductless heat pump? Sounds like ducted, and if so that might be part of it too. The air cools down in the ductwork and if that's not accounted for - i.e. you reuse ductwork that was meant for a furnace – you run into issues like this. And you also need a cold climate heat pump.

(disclosure/transparency I'm the founder of Quilt, a ductless heat pump manufacturer)

[switchbak]

Hi Paul - I'm a big fan of Quilt from Vancouver Island.

It seems to me that you're helping to close the loop on some of the quality concerns that the parent commenter has. Inappropriate sizing/installation and poor product selection seem like common issues from HVAC installers that aren't particularly well versed on heat pumps.

Wishing you continued success, and that hopefully it'll be available in Canada at some point! And also I remember you from the Scala meetup in Vancouver :)

[JeremyPOsborne]

We account for duct losses at Electric Air when sizing. It’s baked into industry standard Manual J sizing calculators and other methods. ManJ isn’t perfect find for this purpose.

In this case, contractor should have advised the heat pump would not keep up and recommended a different solution.

[pfdietz]

When we had our ducted heat pump installed, we also had the ducts in the attic covered with extra insulation, as well as spray foam at the top of the foundation to seal that completely. This all really helped.

[maxerickson]

How is the insulation in the house? Poor insulation and an undersized system will be a bad experience regardless of the heat source.

[baggy_trough]

It wasn't a bad experience before, but now it is, because of: new heat pump

[jcalvinowens]

The radiators might make you feel warmer despite not actually making the air in the room warmer: the black body radiation from the big warm radiators affects your perception of warmth in a not insignificant way.

[card_zero]

Seems to me that making people feel warmer is the objective, and making the air warmer is not.

[Marsymars]

Basically the idea behind infrared (and far infrared) heaters. I'm really curious about them, but there's no good way to trial them without buying and installing.

[ssuds]

I just wrote a big thread yesterday responding to someone with similar concerns to yours (https://bsky.app/profile/shreyassudhakar.com/post/3m3w3nra2h...). Copying it here if it's helpful to other folks. FWIW, the challenges you are facing seem to be grounded in bad design and application, which happens more than it should and really sucks. We need to move the bar much higher for the contractors installing heat pumps. Here's what I wrote on that thread:

This is why contractor & homeowner education are so so so important to get this energy transition right! I always hate to see reviews like this from folks that have installed a heat pump.

It’s almost always a combo of poorly communicated expectations & installer issues.

A few thoughts…

1) “Air doesn’t come out hot” is a common complaint. It’s by design! You don’t need scalding hot air to have a comfortable space. If you’re targeting a 70 degree setpoint, even 80 degree air will get you there eventually. Heat pumps work best when you let them run - they soak the space with heat.

Your furniture, walls, floors all equalize in temp and radiate heat. A totally different form of comfort than standing in front of a vent that blows hot air at you for 5 minutes and then shuts off!

2) AC doesn’t reduce humidity as well. Unfortunately, this is a classic problem with oversized heat pumps. The key to dehumidification is runtime. A well sized system will run for longer, which will pull the humidity out of the space. If the system is too big, it’ll cycle on and off & not dehumidify.

Your contractor should be do load sizing calculations to determine the size of your heat pump, not using rules of thumb or matching the size of the existing equipment! The very best contractors use performance based load calcs, where they look at your past energy bills to size your new system.

3) Supplemental heat runs a lot - this SUCKS. Electric resistance heat is really expensive to run. It really should be something that comes on for emergencies, if ever. Definitely not regularly.

Many contractors set the temperature where the supplemental heat kicks on way too high. You could be running the heat pump (which is way more efficient) to a much lower temperature, but it’ll switch to expensive aux heat instead. Fortunately, the fix to this is simple - just a thermostat setting.

In other cases, they’ll install a cheaper mild climate heat pump in a truly cold climate. This might save money up front, but it’ll kill you in operating costs when you’re paying 4x as much as you could be in the middle of winter to heat your home. The lowest bid could cost you in the long run!

PS - this homeowner later chimed in that swapping the thermostat helped reduce their electricity bill roughly $30/month! A lot of heat pump issues actually boil down to a poorly configured system. Choosing the right contractor is probably the single most important decision you'll make when you get a heat pump installed.

[doctorhandshake]

This. I had 12 contractors come out for an estimate. I insisted to each that I would only consider estimates accompanied by a Manual J (aka show your work). I got 4 estimates with a manual J, and one of them the vendor said ‘despite that the math says you need a 4 ton outdoor unit, I’m giving you two,’ and refused to budge on that.

I went with a vendor who did the math and sized accordingly and my system works great - great comfort year round and very low energy usage.

[Marsymars]

> 2) AC doesn’t reduce humidity as well. Unfortunately, this is a classic problem with oversized heat pumps. The key to dehumidification is runtime. A well sized system will run for longer, which will pull the humidity out of the space. If the system is too big, it’ll cycle on and off & not dehumidify.

What if I want more humidity?

(The traditional way with a furnace would be with a bypass humidifier, where ultimately, the energy to vaporize the water comes from whatever the heat source of the furnace is.)

[twothamendment]

I'm in Northwest Montana. My ground source heat pump doesn't struggle until the highs outside are -20F (actual, not wind-chill). I have the backup heat strip, but the breaker is off. I don't know when it would turn on, I just wanted to know it wouldn't without me knowing it.

[uhfraid]

> “Air doesn’t come out hot” is a common complaint. It’s by design! You don’t need scalding hot air to have a comfortable space.

“It’s a feature, not a bug. Just put on a hoodie and get under the blanket!”

[mulmen]

Where in the system did they install the resistive wires? Is that a defroster on the evaporator (outside) or is it inline with the condenser?

[mrguyorama]

Well

Mitsubishi sells heat pumps that produce 14kw of heat output all the way down to 5f at a COP of 2.3.

Resistive heat has a COP of 1, by definition.

Do you know the size of your oil burner? It's likely over 20kw output.

It's not that pumping heat cannot work sufficiently at cold temperatures, it's that you are expecting the electric car rated 100 horsepower to go as fast as the gas car rated at 300 horsepower.

An oil burner sized to the same output as the heat pump also would not keep up.

If you installed two of those Mitsubishi heat pumps (which would require two independent 240v circuits), you would be at 28kw output and would not need resistive heat strips. These units also claim 75% rated capacity at -13f so that would be about 21kw of heat output even when very very cold.

If your resistive heat strips activate at any point other than extreme weather events or emergencies, your "system" is not sized properly. They are a massive waste of power and money.

A big part of the problem is that the contractors who are essentially the point of sale for these systems are just obscenely dumb about them. They will sell you utterly undersized units or sell units that aren't rated for cold, as well as just install things so poorly that they drain condensate into your walls and cause mold issues. They had similar problems with Oil burners, but at least those they tended to upsell bigger systems so their ignorance didn't matter. They seem very bad at doing the planning or design required to actually spec out a system, so you have to be your own engineer.

>and that is what the industry needs to work on.

I don't know how the industry is supposed to force contractors to read their very very clear documentation, or follow the very clear instructions (of boiler manufacturers no less) of "You must measure heat load to accurately size a heat appliance".

[uhfraid]

Spot on.

[WorldMaker]

The strength of your heat pump shouldn't be outside surface temperature, but underground aquifer temperature. Those two temperatures are related but not as directly as they seem. A good aquifer in certain cavernous regions of the US might stay about 55 degF year round, regardless of outside surface temperature. 55 degF is still below what a lot of people want their home to be year round so a heat pump still has to supplement heat somehow in winters (or radiators or what have you), but a "free" boost to 55 degF is still a better starting place than 20 or 40 degF outside temperature.

I don't think latitude is a factor in how efficient a heat pump you can find, I think the type geography under you feet is (probably where "interior" regions probably have more luck than coastal regions), combined with how well regulated or unregulated your area's aquifer generally is (things like nearby wells and industrial water dumping will effect aquifer levels and temperatures). (Maybe not enough heat pump proponents realize that you only have good, cheap heat pumps if you have a powerful EPA and other Water protection groups fighting the good fight in your region.)

[estimator7292]

You're talking about geothermal heat pumps which are far less common than air-to-air heat pumps because they are far more expensive.

These are entirely disjoint concepts.