> Heat pumps are the greatest thing because the home doesn't go through this massive hot/cold cycle. They might stay running at 10% once they get to temps to keep it at the temps.
That means you have inverter drive. Also nice because they don’t have a capacitor that eventually fails and won’t dim your lights when it turns on. Also great at reducing demand charges if your electric utility bills that way.
But heat pumps can run as an on or off only system. Depends on what you install.
> There is no need to 'rip it out and replace the whole system' to use a heat pump; an air to air heat pump as used in many Scandinavian homes can be fitted at much lower cost without disturbing the existing central heating at all.
I understood that heat pumps work more efficiently in homes that are a) well insulated, and b) where the heating system is designed to work at lower temperatures (bigger radiators/underfloor heating and appropriate pipes). Whether or not a & b are must-haves or nice to have I'm not 100% sure about - I guess it depends.
>Modern heat pumps redirect some heat to prevent the coils from freezing. What you wrote is common FUD pushed by the oil & gas companies.
It's not FUD, and you COMPLETELY ignored & omitted the rest of my sentence from your quote. I'm well versed on how heat pumps work. I was not saying heat pumps don't work below freezing. Rather than simply repeat myself, let me rephrase:
1. Heat pump efficiency gets worse the closer you are to the minimum (outside) temperature they're rated down to.
2. Even with the best (and most expensive) technology, that means efficiency of these units approaches that of a $15 space heater.
3. When it gets TOO cold, they can stop working entirely if they don't have a resistive backup heat system (which, again, is effectively a $15 space heater you paid a lot more for).
Both Canada & the northern US experience these temperatures occasionally (-10f to -30f and worse on some occasions).
Hence the need for backup heat - e.g., a pellet or wood-burning stove, backup furnace running propane or natural gas, or even just something cheap and simple like a $150 portable diesel heater. You don't want to be left without heat in a multi-day power outage after a half inch of ice and high winds.
For backup heat, it's more efficient to burn whatever fuel for heat than run a generator outside to power space heaters or a heat pump at those brutally low temps that often follow those hard ice storms.
> A heat pump is like 5X-10x more costly and requires quite specialist install.
When I shopped heat pumps, the actual unit was about 1.5x the cost of an equivalent air conditioner, and after installation the difference was even less.
> Any programs which promote heat pump installations above a certain scale must either include huge investments into grid robustness or mandate that all heat pump installation must include fuel-based backup heating sufficient for a week or two.
That's a little extreme. You also need to consider your failure modes. I live in texas where a bunch of people died due to an extreme freeze and a very poorly regulated grid. When that happened, it wasn't just electric that was lost, but a big problem was natural gas wells and pipes freezing up too.
The cost to install and maintain both systems would be an automatic deal breaker for many people. I don't think you need total redundancy, but having some is good. For example, I went and bought a "buddy heater" after that freeze. It runs off of a 5lbs canister of propane and has an automatic Carbon Monoxide cutoff. It gets toasty. It won't last forever, but it's a good emergency backup.
One thing I think everyone needs: An emergency radio with crank power. When the grid goes down, so does internet and cell towers. The only way we got news was via radio.
> One big advantage is that they can also be run in reverse
I don't get why this is an advantage. That's just plain old air conditioning, which is genreally considered to be a wasteful, energy guzzling luxury in colder climates.
> Despite the name, heat pumps do not generate heat – they move heat from one place to another.
Literally nothing about "pump" implies it generates heat. That being said...
> In colder climates, an electric heat strip can be added to the indoor fan coil for additional capabilities.
That would just be... electric heating, but with more steps? I mean, at that point you just have a heat pump _and_ electric heating; a hybrid system. It's better, sure, but it's not really just a heat pump anymore.
A heat pump is basically just an air conditioner with a handful of extra parts to allow it to work in reverse. In the US they currently are significantly more expensive to install than AC, but I don't think it will stay that way for ever.
I think part of cost issue is that heat pumps tend to put an extreme focus on energy efficiency, leading to higher up-front costs, whereas AC units tend to balance a little more towards lower initial costs.
Any home that has both gas heating and air conditioning could replace the AC with a heat pump and get more efficient heating for most of the time, while still keeping their existing heating for situations that call for it.
I'm hopeful that AC manufacturers start shifting towards bi-directional units for their lower-cost "regular" segments instead of reserving that for only the fancy super-high-efficiency (expensive) units.
> Why do you say heat pumps only work in well insulated houses with large radiators?
Because heat pumps operate at a lower flow temperature than boilers. Smaller radiators designed to operate at hotter temperatures won't bring your house up to the target heat temperature operating at lower temperatures. They often need replacing. [1]
Trials of heat pumps in existing UK housing have found it difficult giving away heat pumps for free, because of all the extra work required for them to operate properly in the house. [2]
> Heat pumps are ~3x as efficient as the best gas furnaces so why would you need a better insulated house?
Heat pumps in comparison to conventional boilers are meant to be on all the time at a lower temperature, as they take a long time to bring a house up to target temperature.
They depend on good insulation, otherwise the heat never accumulates, similar to if you leave a freezer door ajar, it will never freeze.
> So why would you waste all that energy converting from renewable electricity to hydrogen then burning hydrogen (which is not super efficient anyway)?
At times, renewable energy drives electricity prices negative. We haven't got many ways to store this when it happens, converting water to hydrogen would be a good candidate, which can be delivered using existing gas infrastructure.
> Plus, heat pumps already work at scale
Not in existing UK housing, which would require major changes (insulation, underfloor heating, larger radiators), before they work.
> What about those in the northern half of the US that also need back-up heat for when it is very cold?
This heat pump is supposed to work to -15F and includes back-up resistive heat. Theoretically it can replace a heater and air conditioner anywhere. I know people north of Chicago that use a similar heat pump and resistive backup system and it's been fine to -30F keeping the house at 69F.
> I don't know the contractors they are talking about, but I literally had to say the words "heat pump" to my local Carrier installer and they did all the rest.
There's definitely a bias against them when natural gas is available. Until probably the past 3-4 years very few HVAC contractors in the midwest were familiar with heat pumps or had bad experiences 5-15 years back and recommended against them as it's "too cold" for them to work here.
> so we can see where in the world heat pumps are most effective.
They're not efficient when the temperature drops below a certain point. This is predictable and based on system design criteria. It doesn't mean it's not effective, it's just that it wouldn't be a reliable source of heating year round. It may still make a worthwhile addition to another system, or combined with several other upgrades, may become an acceptable single solution.
> Practically nobody does geothermal heat pumps here. The up-front cost is waaaaaay higher than any kind of normal (for us) set-up, not many people do it so that makes the cost even higher because the installation market is tiny, and energy costs aren't high enough to make the extra tens of thousands of dollars a good investment.
This isn't true in all parts of the US. A family member of mine has had an open loop geo-thermal system for almost a decade now, and they're definitely not the only one in the area.
I'd say about half of my neighborhood has air source heat pumps and about a quarter of the remaining have geo-thermal (vertical loops).
There are two HVAC businesses in my area that specialize in nothing but ground source heat pumps. If there was no market, they'd be out of business.
I think, where I am, it's harder to find a cognizant air source installer. Most of the HVAC businesses here are still under the misconception that air source isn't viable in our northern locale and often don't try to sell, or try to talk people out of them. But my air source is able to heat our house easily at 0F and is rated to run below -10F. It's currently my main heat source. Over the course of winter I'd guesstimate 60-70% heat pump heating overall.
> Then there's the cost. A gas heater is 3 times as cheap, and for that price, 3 times as expensive.
Only really a thing if there's a local gas network and subsised gas.
> Lastly, there's the issue of when it's really cold and the heat pump cannot extract heat from the outside air (this is much less a problem when you have an water to water heat pump, but they are significantly more expensive). Then the thing just runs on electricity. And that can be VERY expensive in certain parts of the worlds.
They work fine in -25c. Few people in the world live in places that are regularly colder than that for significant chunks of time.
In places with mild climates, you might not need anything at all. If you're in a place where it gets hot, a heat pump is practically an exact drop-in replacement for an A/C unit except that it provides heat as well. In my area, you basically can't even buy a one-way A/C unit any more because it's so obviously inferior. If you're in a place where it doesn't get hot (or you've decided to forego cooling in summer), a heat pump is no more expensive, bulky, or noisy than a boiler/furnace setup. Some people don't notice because the old tech came with their house, but that doesn't make it actually good. Again, where I am gas/oil heating is "grandfathered in" for existing homes but forbidden for new construction. The only real competitor to heat pumps is resistive electric. That's cheap and easy to install, and quiet, but considerably less efficient (and does nothing for cooling).
"I don't need/want what a heat pump provides" is not a particularly compelling point when most people do, and even the people who say that often change their tune when they try to sell their now-considered-deficient house.
> Be that as it may, heat pumps at this time are cost prohibitive.
They range from sub-$1K single zone air-to-air wall/window units, to multizone split units, to ground source hydronic boiler/chillers that integrate with baseboard or radiant floors, which can get quite expensive to install, but that's at the high end. Generally speaking they're not really much more expensive than normal air conditioning. I've seen units that come in cooling-only and heating+cooling versions, and the cost difference is marginal (<10%) in those cases.
> You can still use a heat pump that takes the heat from the exhaust air to warm the fresh air
Unless I'm misunderstanding part of this proposed setup, I'm pretty sure this doesn't work. The higher efficiency of heat pumps comes from the fact that the outdoors is an effectively infinite (for the purposes of a house) source of temperature differential. You can only move as much heat as exists, so you can't use a heat pump to multiply a finite heat source.
Then, what's the point? If you still have to have gas lines and infra, just use the gas. It's vastly cheaper.
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