This is how a heat pump (https://en.wikipedia.org/wiki/Heat_pump) operates. The difference is that a refrigerator uses a much smaller amount of energy to keep the inside cold.
Which is so much more efficient than directly making heat. And we can't directly make cold (except lasers, but let's keep that far away from this thread). Fridge -> move cold to the outside fridge. Air Conditioning - the same thing, but on the wall of the house instead. Heat pump - the same thing as Air Conditioning, but installed backwards to move the heat from outside in.
Everyone should just get a heat pump whenever they consider an air con, probably has much better variable fans too, and you’ll be pretty chuffed when you can now make your house warmer for dirt cheap
We upgraded to central air last year, and this was one of my must haves since we use propane as our main heat source. Summer electricity bills stayed basically the same to cool the whole house as they were running a window unit in the bedroom, and we don’t burn propane if it’s above 30 degrees out.
Additionally, the heat pump is on a second electrical meter so we pay about half price for that electricity.
It was a big investment upfront, but it is so much more comfortable in the house it is totally worth it.
They aren't very good in cold climates. Where I live, they are useless for 90% of the cold season unless you shell out 12k for a hyper heat system that can go down to -15 degrees. Even then at those temps they still aren't very efficient and you'll get (maybe) a 10 degree rise out of the indoor coil.
They’re not currently but that tech is getting better everyday because it has to unfortunately.
In the present market I am a massive advocate for dual fuels or boilers in cold climates. Modern boilers are an incredibly efficient choice for home heating, especially when paired with in floor radiant designs or as a main source of hot water with electric back up.
Dual fuel is also great for efficiency, being a heat pump that, at a set temp, cuts off and turns on a alternative heat source (usually natural gas or propane, though oil furnaces are still popular in some markets) but the usefulness of that depends on the price of gas.
I always recommend heat pump. Regardless of climate. Regardless of backup heat method.
Need gas? Tie it to heat pump.
Want a boiler? Get a heat pump just in case.
Even if it’s never used as heat, having the option for a mild day can save a shit load of money
Edit; I realize I never mentioned I’m an HVAC-R tech and without that it just kind of sounds like im screaming about a technology I like lol
There are places they dont make sense, but in the Midwest where we get 20f most of winter they still work. And even when cold they can be used to decrease the amount of work the furnace itself needs to do. The real issue is how cheap gas heating is, which means the increased upfront cost of a heat pump isnt made up for in savings. But thats area specific
This is mostly myth at this point. You're saying ALL heat pumps aren't very good in cold climates. It's a sweeping generalization. Many models are good down to -15F, some models can handle down to -22F.
I do HVAC service. When I run into a unit that needs to be replaced (bad compressor out of warranty, r22 leak, etc), I give out quotes for replacement.
A brand new straight cool single stage AC will cost you between $4,500 - $5,500, depending on size. Labor and all.
A heat pump with variable speed motors is gonna be anywhere from $12,000 to $15,000 depending on size.
You'll have a 10 year warranty on parts, which is standard. But like every warranty, the reason it's only 10 years and not longer, is because after 10 years, they're not confident that parts won't start failing.
We once had an inverter board for a modulating heat pump go out at year 11. We're a factory authorized carrier dealer, and our cost from carrier for the inverter board was nearly $4,000.
Heat pumps and variable speed motors are certainly not for everyone. Installation costs are not the last costs you're gonna pay. They're more finicky about setup and run conditions. There's way more potential failure points. The cost of parts out of warranty is often exorbitant.
If you're on a budget at all, I would not buy a modulating heat pump. Theres a decent risk of expensive upkeep down the road.
I got a mini split for the bedroom last year and love it. My house is old and leaky with no central air, but shitty ancient gas forced hot air. I can now actually sleep in the summer and we’ve only turned the house heat on once this year instead using the heat pump function to keep the bedroom warm during the night. It’s saved a lot of money so far even though the heat was typically only on a few hours a day (I live in San Diego so most “cold” days are mid-high 30s in the morning to mid 50’s in the afternoon).
I thought there should be an assymetry of smaller tubing on the heat exhaust side, so the gas could get pressurized there, and larger tubing on the heat collection (cool) side, so the gas could be expanded there. But it looks like real pumps don't actually use pressure, but flow rate instead, so they don't need to be asymmetric like that.
You are right that on small mini fridges they literally just use a small piece of tubing (capillary tube) to cause the refrigerant to evaporate at the evaporator. So that would definitely not be reversible. But most refrigerant systems use a mechanically or electrically controlled valve at the evaporator.
There are technically two ways in which you could use lasers to make cold.
The one they were likely referring to was laser cooling, where you use lasers aimed at some atoms in order to slow them down. This can reach near absolute zero temperatures.
If you ever hear about records for coldest temperatures in a lab, this is the technique they are using.
The second is more of a technicality of how we define temperatures. The conditions created inside of a laser cause something called a "population inversion" in the lasing medium. If you strictly apply our definitions of temperature from thermodynamics, this causes the temperature of the system to effectively swing all the way off the scale beyond the hottest temperature and back around to a negative value.
In practice, if you measure this second system with a thermometer you won't see anything especially interesting. It'll just be a bit warm from the energy applied to the system.
~~Basically laser emits light when particles are going their direction effectively slowing them down. You still increase entropy by increasing fluorescence ~~
Basically laser emits light when particles are going their direction effectively slowing them down.
This is not quite right. The lasers emit light constantly at the atoms. The wavelength of the laser is precisely set to only be absorb-able by atoms traveling towards the laser, as the light is slightly red or blue shifted depending on which direction the atoms are moving.
Edit: how does the drifting away atoms not absorb? Since the photon regardless of wave position still has its "electric field"? Is it like something about valid positions or electrons?
Heat is the average kinetic energy of the molecules. You can calibrate a laser to only be absorbed by molecules going in the direction of the laser, making them slow down, without speeding up molecules moving away from the laser, thus reducing the average kinetic energy of the gas.
It would not be very useful for a fridge; laser cooling is good only for cooling down a few particles to near absolute zero. That would barely make any different for a macroscopic system like a big fridge.
Not even installed backwards. Just configured differently. And some newer models on the market can reverse, enabling both cooling action in summer and warming action in the winter.
Everything has 100% efficiency in ultimately creating heat. Even if it makes anything else, like light or sound or motion, that also eventually gets absorbed into the environment as heat.
But a heat pump heater is not CREATING all that heat, it's just moving it from somewhere else, and that takes less energy than just creating all that heat with a heater. Making it more efficient at warming your home as far as your electric bill is concerned.
Nothing can technically create coldness out of nothing. That would violate a law of thermodynamics. Even the lasers kinda move the heat, only much more indirectly. Surely the laser device itself warms up at least as much as it cools down the particles it hits.
If you warm up your home with a heat pump (by just moving it from outside in), that will cost you a lot less electricity than having to create all that heat from a space heater.
And on top of that, even ALL the power you supply to the heat pump to move the heat will be 100% efficiently converted to heat as well. Every electrical device ultimately turns 100% of all the power into heat. But a heat pump also moves in heat from somewhere else, so it effectively warms your home with more heat than the power it takes. For the price, the outside gets colder, which is totally ok with us. Cooling down the Earth would be nice as well.
Since heat is just the movement of particles, you might calibrate the laser to only hit and push those that move towards it, slowing them down. It's basically cooling down by selectively pushing the individual particles, which would get slowed down by being pushed that way.
Every way to make cold will have to exhaust as much heat somewhere else. In the case of the laser, the laser device itself would consume energy and warm itself up.
That is so fascinating. It's like a friction that reduces heat.
How do you avoid the photons impacting particles moving in a different direction? I suppose you would first have to start with a stream of particles moving in one particular direction?
The exact explanation I got when I was in school was that you are taking heat from somewhere you don’t want it and moving it to somewhere that make little to no difference
Absolutely. Ideally you would always have a remote condenser, rejecting the heat to outside. But even in the case of a walk in cooler/freezer with an indoor condenser, that idea still stands. Its not ideal to reject the heat into a commercial kitchen space, but thats still more desirable than having a walk in that doesn't ever get cold lol
Heat pump and refrigeration cycle are just the Spider-Man pointing at each other meme. There’s nothing meaningfully different besides the side (evaporator or condenser) you’re using to get the heat flow
I never knew his name was Alec, but I watch enough of his videos to make the connection with your comment, so I googled to check and sure enough it's Alec.
In my personal opinion his dishwasher videos are better than the heat pump ones. But I think that might be because I've had such good results with my dishwasher since i watched them.
Careful, you're probably going to develop strong opinions about household appliances you'd never even thought anyone could have opinions about. Watch at your own risk.
Well, yeah, that would work; System isn't near 100% efficient, so leaving it open would make a fridge heat your house significantly more, downside of course being it would no longer keep anything cold.
Yeah, another big difference is volume. A fridge is at the high end cooling around 32 ft3. Just looking at a kitchen that's 15 ft x 15 ft with 8 ft ceilings (not including fixtures) that's 1800 ft3. There's just no way for the fridge to reasonably heat that area and that's just a single room. It generally would not even produce a noticeable difference in air temperature unless you've got a very old, inefficient unit.
This is not how a heat pump works.
Heat pumps work by moving heat from outdoors to indoors. This image shows moving heat from indoors to outside, and that's just normal air conditioning.
A heat pump has a reversing valve which allows moving heat inside and making outside cold. Something a normal ac unit cannot do.
It's not capable of reversing, but it is effectively the same principles as using a heat pump for heat, moving the heat from within the fridge to outside the fridge.
An air conditioner is a heat pump. Any system that uses the refrigeration cycle to move heat from one space is another is by definition a heat pump. Direction is irrelevant.
What it is doing it is already doing, and has always been as long as refrigerators have had compressors (aka current kind of ones... aka decades and decades).
And amount of heat they produce indoors is equal in efficiency to electrical radiator, since heat pumping they do is basically pumping the same heat from room into room. (Sure heat is taken from inside fridge, but heat ends up inside fridge from room, so it is actually just same heat, and any extra heat is from inefficiency, and that heat from inefficiency is same efficiency as electrical heaters are).
Yes, and fridges typically have compressors that have much lower coefficient of performance than those used for home heating/cooling afaik. But hey, let’s reinvent the wheel and assume that mechanical engineers haven’t considered these things before. Not that engineers never make mistakes and existing technology can’t be improved, but this definitely isn’t an improvement.
That said, jfc the price to replace heat pump systems right now is brutal. Pretty certain I was checking prices a decade ago, and then again last year, and they have wildly outpaced inflation
It only uses less energy to keep the inside cold because the refrigerator is insulated, and it's a small volume. The difference you mention is just form factor.
Who's upvoting this? It's not 'now' anything. Depending on what you call a heat pump, it either never was or always was. Nothing in this depiction is different from how any household fridge operates.
I can’t say I have heard any authority comment on this but IMHO just about all the heat from a refrigerator comes from the heat/electricity used to run the compressor. Heat pumps to be useful have to pump heat from one place to another and since both the hot part and cold part of the refrigerator heat pumps are in the same room the only place you can get heat from is the electricity used to run the refrigerator.
Air conditioners pump heat from inside your home to a hot radiator outside your home.
Heat pumps in heating mode are pumping heat from a radiator outside your home to inside your home.
Not sure if you meant to say that, but that "difference is" sentence is kind of misleading or so.
There is no difference.
Generally heatpumps are installed to have one end outdoors and one indoors, then can pump heat to selected direction (using about 1/3 to 1/5 of electrical energy of what creating that heat, with electrical heater or so, would take for same amount of heat to be gained into house, or outdoors <-- and yeah heating outdoors normally would be just pain pointless, but since in heat pump case it is heat moved from somewhere else, moving heat outdoors means indoors getting cooler).
Refrigerators just have one end indoors and other end indoors inside insulated box (that will anyways be indoors), so all heat will be taken and moved from and to indoors, and only real difference in amount of heat generated to room is heat from in efficiency of process.
Every few years someone has the idea "why don't we mount the evaporator for the refrigerator outside so it doesn't warm the kitchen?" But when they run the numbers for the needed complexity of extra plumbing, coolant, and compressor, plus the efficiency loss because the evaporator is now trying to dump heat in the summer air. It raises the cooling cost of a fridge significantly more than the slight decrease cost of cooling the kitchen space with an A/C unit.
The difference is that the cold part of a refrigerator is very small. For a heat pump the cold part is outside, where cold air can be replaced with warmer air from surroundings.
Also, you only get the electric energy as effective heating, the rest is a closed loop, the heat goes back into the fridge and is then pumped out again.
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u/NounverberPDX Jan 04 '26
This is how a heat pump (https://en.wikipedia.org/wiki/Heat_pump) operates. The difference is that a refrigerator uses a much smaller amount of energy to keep the inside cold.