How a heat pump works • Hacker News Board

Re: How a heat pump works

#151

Post by mikeyouse » Fri, Feb 10, 2023, 4:14 PM UTC

nashashmi wrote: post #13

boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

Heat pumps are the opposite of AC. AC industry is behind this for sure. It is like a paid PR campaign. It is not more economical then gas. So now gas is going to be punished for factors X,Y,Z. It is coordinated. I wish there is more investigative research into who and why they are doing this.

Ah yes, "big AC" is bullying the Oil and Gas industry with their subversive marketing. If only Exxon, BP, and Shell had some political clout they could expose this plot.

Re: How a heat pump works

#152

Post by boucher » Fri, Feb 10, 2023, 4:17 PM UTC

nashashmi wrote: post #122

SigmundA wrote: post #68

Earlier quoted context omitted.

They can be, natural gas is about 1000 BTU per cubic foot. An expensive high efficiency gas furnace might be 95% efficient (most normal furnaces are in the 80's) 1000 x 0.95 = 950 BTU/cuft A high efficiency natural gas power plant is 60% efficient and a modern high efficiency low temp heat pump can have a COP up to around 2.7 at 17F 1000 x 0.6 x 2.7 = 1620 BTU/cuft A 40% power pant is still more efficient than a 95%…

I am in NY. And I think for Florida, a heat pump makes because of a hybrid AC model. Even if electricity is more expensive, the equipment and energy cost of a separate unit is not worth spending. In extreme climates, gas burning is cheaper. And quite clean. There are some objections because of delivery leaks, but that is a separate concern.

As pointed out by several other comments, you're very off base about heat pump efficiency and about natural gas being "clean."

Switching everyone to heat pumps would lower emissions from heating and cooling in the US by 160m tonnes a year [1], which is something like 30-40%.

It's true that upfront costs of heat pumps can be higher, but thanks to the IRA there are huge subsidies available (and further subsidies in many states) which make up most or even all of that difference. The lifetime costs of heat pumps with these subsidies should be substantially lower than high efficiency natural gas furnaces.

[1] https://www.rewiringamerica.org/circuit-breakers-heat-pumps

(Those subsidies, by the way, are one of the reasons "everybody is talking about heat pumps")

Re: How a heat pump works

#153

Post by sophacles » Fri, Feb 10, 2023, 4:18 PM UTC

billjings wrote: post #148

boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

Here's a couple of reasons: 1. The American market has a lot of incorrect perceptions of heat pumps. Debunking these makes for great viral content! 2. The IRA introduced big incentives for various electrification expenses. The incentives are the big thing, but the public interest/controversy part is why some enhancements like heat pumps and kitchen electrification ("don't take away my gas stove!") are going more vira…

What is IRA in this context? I don't think heat pumps have anything to do with retirement nor the political status of Norther Ireland.

Re: How a heat pump works

#154

Post by mikeyouse » Fri, Feb 10, 2023, 4:19 PM UTC

endemic wrote: post #114

MrMan wrote: post #23

Earlier quoted context omitted.

gas stoves are bad

I don't understand why this is contentious. You're burning gas inside your house.

That's what is funny to me too -- they're basically phasing out all furnaces and hot water heaters that aren't direct vent (bringing in combustion air from outside) because it's so problematic to have gas-burning appliances in your home. Yet we just burn gas stoves -- some of which are massive without question...

If you were to use all of the burners on this stove on their highest setting, it would consume more BTUs than a 6-ton Furnace! And it just vents into your indoor air: (https://www.homedepot.com/p/Cosmo-36-in-6-0-cu-ft-Commercial...)

Re: How a heat pump works

#155

Post by notyourwork » Fri, Feb 10, 2023, 4:19 PM UTC

fullstop wrote: post #45

notdarkyet wrote: post #34

Earlier quoted context omitted.

I see this as well and it looks to be multiple people buying in to the campaign, especially here on HN. Having lived in a new, high end apartment that had a heat pump for both heating and cooling for 3 years, I am very unimpressed with the tech. Running nonstop, couldn't heat/cool above/below a certain threshold. Electric bill very high. Clogged and broke a lot. If the general radiant heat and cooling from being in l…

Your high end apartment must have had a low end heat pump installed. In the midwest a geothermal heat pump would work wonderfully. Also, they are designed to run constantly in order to maintain the set temperature -- it's not like a natural gas fired furnace where it quickly reaches the set point.

The constant running also affords a more consistent temperature because air is continually moving. Decreases the temperature variance throughout the zone. I have a 3 zone heat pump, 2 single room zones upstairs and a main floor with a air handler. We LOVE the setup so far.

Re: How a heat pump works

#156

Post by snuxoll » Fri, Feb 10, 2023, 4:19 PM UTC

nashashmi wrote: post #125

snuxoll wrote: post #104

Earlier quoted context omitted.

> this is a no brainer in milder climates which is why I have a heat pump and no gas furnace here in FL even though I have gas to the house for other uses. They're a no-brainer in every climate. Newer heat pumps can handle fairly cold temperatures (-13°F) pretty easily, there may be a loss in efficiency but in the majority of the world it doesn't stay that cold. A few days of lower than normal efficiency, and at wors…

Ok! I am genuinely interested in how heat pumps are more efficient. My online search led me to calling heat pumps more efficient when compared to electric heaters. And better in other ways compared to gas burners. But lord's sake, they were all upselling marketing sites for heat pumps. I am looking for genuine research, and not from paid mouth pieces. Majority of the comments here seem like agents of heat pump indust…

Physics. When combusting fuel you cannot get more heat energy out of them than the chemical bonds you are breaking contains, a gas furnace can never be more than 100% efficient, the best commercially available ones are 95%, and a majority that are actually installed are closer to 80-90%.

Heat pumps do not create heat, the refrigeration cycle moves heat from point A to point B. For every KWh of electricity used by your refrigerator, air conditioner, or heat pump, 3-4 KWh of heat energy can be moved where you want it to go.

Even if you have a (comparatively) inefficient combined cycle natural gas power plant that is 50-60% efficient, you're still getting 150-200% efficiency for heating with a heat pump compared to 80-95% for a natural gas furnace.

I live in Boise so we have pretty cheap utilities compared to the national average, but here's some math:

1 therm (~30KWh of energy) is ~$0.72 from Intermountain Gas, the furnace in my rental is 90% efficient, so I actually get 27KWh of heat from every therm I burn.

Idaho power has a tiered tariff for residential customers, with a peak charge of ~$0.098 per KWh during the winter for usage over 2,000 KWh in a month.

Every therm my gas furnace burns costs me as much as ~7.5KWh from the electric utility, but those 7.5KWh can provide me with 30KWh of heat with a quality heat pump, which would require a 100% efficient natural gas furnace to reach. Add in that gas furnaces have a much higher TCO because of maintenance and repair compared to a heat pump, and they're not just energy inefficient in comparison but even just plain more expensive to operate even with incredibly cheap fossil fuels.

Re: How a heat pump works

#157

Post by baxuz » Fri, Feb 10, 2023, 4:20 PM UTC

nashashmi wrote: post #113

pjerem wrote: post #50

Earlier quoted context omitted.

Yes they are. You get more heating from an heat pump running from electricity coming from gas plants than what you get by just burning the gas. Including losses on the grid.

I cannot imagine this in anyway. Heat pumps work like ACs do. They do compress a medium till it heats up, and then spread that heat around. And then they decompress until it cools down and dump that cold until outside heat brings up the temperature again. Those compressions and decompressions take up immense amounts of energy. They are less efficient than simply burning gas. On the flip side, could we not create elec…

That's the whole point. For most modern systems you get >4x of the energy in heat exchange compared to the energy you put in. You don't produce heat, you exchange it.

https://www.wolf.eu/en-de/advisor/cop-heat-pumps

Re: How a heat pump works

#158

Post by tekla » Fri, Feb 10, 2023, 4:20 PM UTC

sophacles wrote: post #153

billjings wrote: post #148

Earlier quoted context omitted.

Here's a couple of reasons: 1. The American market has a lot of incorrect perceptions of heat pumps. Debunking these makes for great viral content! 2. The IRA introduced big incentives for various electrification expenses. The incentives are the big thing, but the public interest/controversy part is why some enhancements like heat pumps and kitchen electrification ("don't take away my gas stove!") are going more vira…

What is IRA in this context? I don't think heat pumps have anything to do with retirement nor the political status of Norther Ireland.

Its a fairly easy to parse typo of IRS.

Re: How a heat pump works

#159

Post by mikeyouse » Fri, Feb 10, 2023, 4:20 PM UTC

asow92 wrote: post #73

prottog wrote: post #57

Earlier quoted context omitted.

In the Northeast with that much square footage, you would be better off with ground-source heat pumps (whether open or closed loop), rather than the normal air-source heat pumps.

I guess the concern I have with all this is that my current system works well, and I don't want to spend $10K+ unless it brings down my heating costs significantly. Could a ground-source heat pump system do that?

What do you use to heat your water? If it's natural gas, it's likely close to making sense. If you use propane, it definitely makes sense to switch.

Re: How a heat pump works

#160

Post by boucher » Fri, Feb 10, 2023, 4:22 PM UTC

bcrosby95 wrote: post #64

Maxburn wrote: post #33

Earlier quoted context omitted.

YES. There is a massive electrification push right now because electric items can be fed from "sustainable" things like wind/dam/solar and don't emit CO or CO2 in operation. Heat pumps are also inexpensive on initial cost and less expensive than straight AC with gas heat. They are also low maintenance in comparison to straight AC with gas heat. Very popular units in southern US.

This hasn't been my experience. I can get an AC unit and gas furnace installed for something like 7k. But a heat pump unit that heats and cools is something like 13k installed. I obviously went with the former.

It's worth mentioning that the Inflation Reduction Act is now providing for substantial subsidies for purchasing heat pumps (and other home electrification projects).

Anyone doing the math today on a similar purchase should really check out how much they can get from the government: https://www.rewiringamerica.org/app/ira-calculator