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Nine US states are teaming up to accelerate the adoption of heat pumps

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Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#431

Post by Aloha »

stephen_g wrote: post #401
Aloha wrote: post #372

Earlier quoted context omitted.

I don't think your math adds up. Combined cycle is like at most 70% efficient, subtract 10% of distribution, you end up with 60%. At 50f my 5T heat pump takes 6.6 kWh to generate 50,000 BTU. 6 kWh of energy takes 71cf of gas to make - accounting for transmission and generation losses. 71cf of gas will make 71,000 BTU of heat, assuming an 80% efficiency furnace, that comes out to 56,000 BTU usable. Yes a heat pump wil…

What kind of system do you have that is only giving you (if I’ve converted the those very confusing units correctly) a COP of 2.2 at 10° C? That’s really very poor… There are air-to-water units that can achieve COP > 4 at 0° C, and even a good air-to-air should still be over COP 3… I’d expect to see a COP like that at -15° C or below on a modern unit…

Should have been 60,000 BTU, I read the wrong column

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#432

Post by PaulDavisThe1st »

bbarn wrote: post #411
Areading314 wrote: post #406

Earlier quoted context omitted.

Solar isn't a useful source of energy for heating in California, since the demand is almost entirely during winter mornings/evenings where the sun is down.

Solar with Battery storage is a very useful source for heating energy, even in the coldest climates in CA. Even in the mountains where it drops below freezing at night, most places it's still sunny a lot more than the US average during the day. Most Battery setups I know of target a 4 day stretch of cloud cover for storage capacity, so it is certainly an option. Where I live at 7000 feet, we have so much sunshine, ev…

Where I live, at 6200 feet, we have oodles of sunshine. Even so, the air-source heat pumps in my old adobe use 3x more than we generate (which in turn is 3x more than we need during the summer). No (sane, residential) battery system can handle this.

Which mostly goes to show the value and necessity for serious insulation and air-sealing, which this house does not have. Nevertheless, the point about batteries remains.

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#433

Post by Fuut »

demondemidi wrote: post #334
Fuut wrote: post #180

Earlier quoted context omitted.

This is just not true at all. Why do you even respond if you don't know enough about heat pumps?

Oh, sorry, I guess I was brainwashed by the "anti heat pump mafia". I had this conversation with three HVAC installers but according to this thread any HVAC installer that speaks ill of heatpumps is old and stupid. Recently, I stayed at an AirBNB recently that had a heatpump and the temps dropped during the deep freeze and it was running 100% of the time and failing. The AirBNB owner said it was brand new and I would…

You clearly don't know if this is your only source.

"Below 0° Fahrenheit, heat pumps can still heat your home with more than twice the efficiency of gas heating or standard electric heating (such as electric furnaces and baseboard heaters). They’ve been tested and approved as far north as the Arctic Circle, and are popular options in very cold countries like Finland and Norway."

Finland has over 60% heat pumps.

And heat pumps, just to be clear, work by generating a temp difference. The main problem is the efficiency and that drops also because there is a heating cycle needed for the air intake.

How many models did you actually research yourself?

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#434

Post by lazide »

clhodapp wrote: post #392
jrockway wrote: post #381

Earlier quoted context omitted.

Emergency heat was under-installed. In the midwest, you have to have it, and it will suck down a ton of electricity for the handful of days a year you need it. Being entirely reliant on mini-splits without resistive emergency heating is a very strange choice, and it's not what heat pump advocates are recommending. The idea behind heat pumps is to eliminate the need for the natural gas distribution infrastructure. As…

Aren't space heaters and emergency heat essentially the same thing? It seems strange for the city to ban space heaters when they really ought not to be worse than any other resistive heater

They’re exactly the same efficiency (100% electrical power to heat), with the caveat that space heaters tend to be more of a fire danger as they’re temporarily connected.

Resistive baseboard heating is the permanent option.

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#435

Post by aero_code »

Aloha wrote: post #372
Retric wrote: post #349

Earlier quoted context omitted.

In the continental US you get ~2x the heat from burning natural gas in a combined cycle turbine to run a heat pump than you would from using a high efficiency gas furnace. The market price of electricity vs gas varies quite a bit through time and various distortions of the market. Currently gas is cheap, but you want to compare historical averages when buying something that lasts 15+ years not simply look at current…

I don't think your math adds up. Combined cycle is like at most 70% efficient, subtract 10% of distribution, you end up with 60%. At 50f my 5T heat pump takes 6.6 kWh to generate 50,000 BTU. 6 kWh of energy takes 71cf of gas to make - accounting for transmission and generation losses. 71cf of gas will make 71,000 BTU of heat, assuming an 80% efficiency furnace, that comes out to 56,000 BTU usable. Yes a heat pump wil…

I don't think the numbers are accurate in the quantity of gas. Since kWh and BTU are both units of energy, finding the cf of gas is unnecessary (assuming the efficiency numbers are correct).

1 kWh = 3.6 megajoules and 1 BTU = 1055 joules

The 6.6 kWh of the heat pump is 23.76 MJ which is 22,521 BTU of energy. Assuming that the power plant and distribution are 60%, it would take 37,535 BTU of gas to produce (22,521/60%).

Instead, using that 37,535 BTU of gas in an 80% efficient furnace would only produce 30,028 BTU of heat, which is worse than the 50,000 BTU from the heat pump.

I'm pretty sure even a poor heat pump will be more efficient than heating directly with gas. (Of course, they have drawbacks, like they can leak their refrigerant that causes more of a greenhouse effect than CO2.)

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#436

Post by PaulDavisThe1st »

newZWhoDis wrote: post #364
david422 wrote: post #270

Earlier quoted context omitted.

I use solar, but using heat pumps and an electric car uses maybe 3x more electricity than my roof can produce.

Higher efficiency panels + vertical panels would help. Most houses have decent south-facing walls. Ground mount is also an option in many places.

6.7kW ground mount here in NM, still can't heat my home in winter in this climate (would need 21kW with my Mitsubishi hyper-heat units). We have relatively OK passive solar contributions too.

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#437

Post by thsksbd »

jefftk wrote: post #311
david422 wrote: post #265

Earlier quoted context omitted.

I think you are back to where you started. If it was cheaper to use gas to run a heat pump then everybody would just run generators in their houses off of gas instead of using electrical lines.

In MA this actually does work at first glance: a 23% efficient Generac 7171 is rated for 9kW at full output on natural gas, and uses 127 ft3/hr (1.37 therms). This is $0.30/kWh at $2/therm, compared to the $0.323/kWh I pay the power company. If you were doing this for real you'd put in the work to find something more efficient than this unit, which would then be enough to make up for the cost of the generator and the…

Why isn't it legal? Is that an MA thing?

If you plumb the radiator to your home you get >100% efficiency

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#438

Post by jackson1442 »

clhodapp wrote: post #392
jrockway wrote: post #381

Earlier quoted context omitted.

Emergency heat was under-installed. In the midwest, you have to have it, and it will suck down a ton of electricity for the handful of days a year you need it. Being entirely reliant on mini-splits without resistive emergency heating is a very strange choice, and it's not what heat pump advocates are recommending. The idea behind heat pumps is to eliminate the need for the natural gas distribution infrastructure. As…

Aren't space heaters and emergency heat essentially the same thing? It seems strange for the city to ban space heaters when they really ought not to be worse than any other resistive heater

I imagine the ban on space heaters refers more to their fire risk, since emergency heat would be permanently installed in a location where there’s not any flammable materials but a space heater can be placed right next to any number of flammable things.

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#439

Post by jjeaff »

clhodapp wrote: post #392
jrockway wrote: post #381

Earlier quoted context omitted.

Emergency heat was under-installed. In the midwest, you have to have it, and it will suck down a ton of electricity for the handful of days a year you need it. Being entirely reliant on mini-splits without resistive emergency heating is a very strange choice, and it's not what heat pump advocates are recommending. The idea behind heat pumps is to eliminate the need for the natural gas distribution infrastructure. As…

Aren't space heaters and emergency heat essentially the same thing? It seems strange for the city to ban space heaters when they really ought not to be worse than any other resistive heater

People do dumb things like put a space heater on their bed or under a shelf full of papers. With heat strips, the resistance portion is built in.

Re: Nine US states are teaming up to accelerate the adoption of heat pumps

#440

Post by turtlebits »

mauvehaus wrote: post #277
turtlebits wrote: post #218

Earlier quoted context omitted.

Yes, HVAC contractors in the US massively overcharge. I saved ~ 10k doing the install myself. The equipment is inexpensive, labor can be upwards of 2x equipment cost.

I looked into doing my own heat pump install. At least here in Vermont, you can't buy one without a refrigeration license[0] because of the ozone depletion issues with refrigerants. You also have to buy one from an in-state supply house to qualify for some of the incentives. Not all supply houses will sell to muggles. My experience was that it was simpler and quicker to pay someone despite having basically the simple…

Buy one that has precharged refrigerant in the condenser. New units use R410a which does not deplete ozone. You'll also never need to handle refrigerant, only open a valve which release it into the copper lineset.

You can buy a Mr Cool unit, you won't need to cut/flare/vacuum the lineset, just connect. I don't personally don't use them as their units generally cost a bit more, (30$ ~ 50%) and you're stuck with whatever lineset lengths they offer. However it's a great starter install and work just fine.

Cooper-Hunter units come precharged, so fairly easy to DIY.

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