Heat pump vs non heat pump. What is the difference in efficiency

[Just Lurking]

I live in the cold. Just south of Ontario in NY on the south bank of the St Lawrence. I have heat pumps / minisplits for my house. When it’s cold out, 15°F and under, my heat pumps, which are specially certified for the cold I live in, quit working. They spend more electricity cycling a defrost mode, during which the house is getting colder and colder, than they do warming up the house.

Do you happen to know what brand and model heat pumps you have? In particularly high moisture environments there are additional considerations to ensure comfort and functionality (such as raising them up high, avoiding exposing them to excessive wind, etc.) The below video has a nice overview of heat pump defrost cycles, why they happen, and how they can be mitigated to maintain comfort:

With that said, the numbers you've given are great. We need to have that level of heat pump tech in some parts of the States.

You can get it via imported equipment right now (Mitsubishi is probably the most common but others exist). In terms of local brands, it's coming, slowly, but seems to be coming. The DOE has a cold climate challenge which seems to be helping slowly nudge local HVAC manufacturers to up their game:

https://www.energy.gov/eere/buildings/residential-cold-climate-heat-pump-challenge

I just hope they have additional electric resistance heaters for those times the temps drop below 35-40 (Fahrenheit; about 2-5 centigrade for those who use those units).

I don't know what available in the automotive world nor what Ford has sourced for the Mach-E, but modern cold climate heat pumps work far below those temperatures. The DOE Cold Climate challenge (referenced above) has a -15°F (-26°C) test that several manufacturers are close to achieving (imported heat pumps can already achieve this) and a less challenging -5F (-20C) challenge that several both domestic and import manufacturers can already achieve with products on the market.

Sponsored

 

[grein002]

Waste heat is already going into the cabin on the current MME. You can’t get any more efficient than directly using waste heat.

Resistive electric heaters are the most responsive. My Subaru had resistive heaters in order to provide instant heat and would switch over once the engine heated up.

the problem with the MME is the electric is used to heat everything and isn’t powerful enough to heat both cabin and battery in extreme cold. Unfortunately, heat pumps lose efficiency in extreme cold. The 2024s have a more powerful electric heater which will help and the heat pumps will increase efficiency by a bit in moderate cold.

I believe the heat scavenging (and higher 7kW resistive heater) were both added on the 23.5 models.

 

[Space_Pony]

I live in the cold. Just south of Ontario in NY on the south bank of the St Lawrence. I have heat pumps / minisplits for my house. When it’s cold out, 15°F and under, my heat pumps, which are specially certified for the cold I live in, quit working. They spend more electricity cycling a defrost mode, during which the house is getting colder and colder, than they do warming up the house. So I have to kick the propane forced air furnace on.
So take my heat pumps, and add the cooling effect of airflow from driving… nah, I’m good. I’ll keep my resistive heater. Sure it costs range. A heat pump might be more efficient above 32°F, but once it’s below freezing, it’s going to work less and less until it just can’t keep up. At some point it will be using just as much range, only without producing any actual heat.

I’ll keep my resistive electric heat.

I have a ground source(geothermal) heat pump for my home. It never uses the backup resistance heat down to -20F and it never defrosts. I had an air source heat pump that was worthless below 20F.
I doubt if a heat pump on the MME will make too much difference unless you are traveling for a couple of hours and it's above 30 degrees.

 

[Jimrpa]

Do you happen to know what brand and model heat pumps you have? In particularly high moisture environments there are additional considerations to ensure comfort and functionality (such as raising them up high, avoiding exposing them to excessive wind, etc.) The below video has a nice overview of heat pump defrost cycles, why they happen, and how they can be mitigated to maintain comfort:

I do not know the model, but the outside unit (compressor) reads “Trane” and sits in a small concrete pad on the ground.

 

[Jimrpa]

I have a ground source(geothermal) heat pump for my home. It never uses the backup resistance heat down to -20F and it never defrosts. I had an air source heat pump that was worthless below 20F.
I doubt if a heat pump on the MME will make too much difference unless you are traveling for a couple of hours and it's above 30 degrees.

Sadly, my HOA would never allow me to put in a ground source heat pump. I’d love to get one.

 

[Space_Pony]

Sadly, my HOA would never allow me to put in a ground source heat pump. I’d love to get one.

It helps if your home is on 25 acres and have a horse pasture to bury pipes. What's a HOA? ?

 

[Jimrpa]

It helps if your home is on 25 acres and have a horse pasture to bury pipes. What's a HOA? ?

Nice. My home is on about 2,500 square feet and the land outside the outer envelope of the home and structures has an easement for the association to maintain it.

 

[Zardoz]

You can get it via imported equipment right now (Mitsubishi is probably the most common but others exist). In terms of local brands, it's coming, slowly, but seems to be coming. The DOE has a cold climate challenge which seems to be helping slowly nudge local HVAC manufacturers to up their game:

The last time I went down the research hole about heat pumps was nearly 10 years ago and the situation sounds unchanged. Cold climate heat pumps in the US are like fusion power... perpetually just around the corner.

 

[Just Lurking]

The last time I went down the research hole about heat pumps was nearly 10 years ago and the situation sounds unchanged. Cold climate heat pumps in the US are like fusion power... perpetually just around the corner.

That's just not true. There are cold climate heat pumps available in the US from Mitsubishi, Daikin, Gree, Midea, Trane, Lenox, LG, Fujitsu, and more. The DOE initiative is focused on building up local manufacturing and local technology of CCHPs, which is admittedly still a work in progress but heading in the right direction.

 

[Zardoz]

That's just not true. There are cold climate heat pumps available in the US from Mitsubishi, Daikin, Gree, Midea, Trane, Lenox, LG, Fujitsu, and more. The DOE initiative is focused on building up local manufacturing and local technology of CCHPs, which is admittedly still a work in progress but heading in the right direction.

Oh, ok, I read your previous post as though the cold climate options had to be imported and were not readily available in the the US. When I was shopping 10 years ago Mitsubishi had a very promising solution but it was for sale in Canada and not the US. I assumed that's what you meant by 'imported'.

I perceive "cold climate" as greater than 100% efficient at temperatures somewhere in the range of -10F to -20F (or colder).

 

[MrLoganRoss]

I have an apple's to oranges comparison, but it might help....

I went from a 2023.5 MME CR1 to a 2024 Lightning Pro (heat pump). I am on the Olympic Peninsula in the NW corner of NW Washington, across the Strait from Victoria Canada. We have had a few cool mornings already so plenty of chances to use the Lightning heat. I had CarScanner set up in the MME and now on the Lightning to watch the heater and air conditioner usage.

The MME would use up to 8kW on the heater when I called for it. The MME heated up very quickly, turn the heat up and it got warm in the cabin, no hesitation. I kept the MME temp pretty consistently at 68 deg F and it was always comfortable. The efficiency hit was obvious while driving as my normal was around 3.2 MPK and if using heat would quickly go into the mid-high 2.x MPK, even lower if it was really cold.

The Lightning doesn't warm up nearly as fast. The heater generally bounces between 0-4 kW and the "air conditioner" (heat pump) spools up and down, but tops at about 9 amps total (it only shows amps in CarScanner for the AC, not sure if it's off the 12 volt or the HVB. If 12 volt, then it's about 110 watts (per @Snakebitten it's 240 volt so that's about 2200 watts)). I adjust the Lightning cabin temperature anywhere from 68 to 76, and usually keep it around 72 to get comfortable. The heat is much slower to come no matter where I adjust it. Efficiency wise, my normal in the Lightning is 2.4 MPK. With the heat blasting, it goes to about 1.8. In normal cruising with it set to 72, I get about 2.2 MPK in cool weather.

Yesterday the kids and I got hit with a cold driving rain that turned into a windy thunderstorm during their soccer practice. After the thunder hit we cancelled practice and got into the Lightning, all cold and wet. I cranked the heat to max, it very slowly got warm. The outside temp showed 46 F. I wish I had the instant MME heat... The Lightning was much more like an ICE vehicle, I had to wait a while for it to heat up. CarScanner showed my air conditioner at 9 amps pretty consistently, and the heater was late to the game, and cycled on and off from 0-4. We waited about 5 minutes while we warmed up and waited for the window fog to clear. I was at "Auto 3 (high)" and heat to "MAX" with the seat heaters on high.

All of this to say that the heat pump is not a godsend, but it's not terrible. I think it is more efficient than the resistance only heater, but not nearly as quick to heat. The lowest outdoor temp that I have driven in so far is 40 deg F, so no real world comparison in really cold temps yet.

I have them same pair of vehicles as you. I haven’t paid attention to timing between the two, but don’t have any issues either. I would say that the Lightning cabin is much bigger and I would expect it to take longer.

I am curious now and will be observant (subjectivity, with out monitoring) and I will report back.

 

[MrLoganRoss]

I believe the heat scavenging (and higher 7kW resistive heater) were both added on the 23.5 models.

Correct

 

[devmach-e]

The last time I went down the research hole about heat pumps was nearly 10 years ago and the situation sounds unchanged. Cold climate heat pumps in the US are like fusion power... perpetually just around the corner.

You would be wrong. They work very well these days. Down to -20F or lower.

 

[therealpinto]

This is a far more complicated calculus than we are likely to understand.

For simplicity sake a resistive heater creates heat at a 1:1 ratio, a heat pump CAN OPERATE UP TO 1:3 (or more, but probably not in a car) meaning they can transfer 3 watts of heat for 1 watt of input.

But this is far from simple as a heat pump has a duty cycle, what your car actually needs i.e. the battery, cabin, outdoor temperature, blah blah blah.

In the end why nobody REALLY cares is this only really matters in max range cases in colder weather where charging is hard to come by, otherwise does it REALLY matter?

However the car SHOULD BE more efficient with a heat pump, so hard to say why not have one (and we've just told it does) in the future.

The statement "nobody REALLY cares" may be a bit off though as it is not really universal across the globe. For Northern Sweden, where I live and drive my Mach-E, the combination is that we have cold weather (sometimes really cold, I drove in under -34 C or -29 F last year) but also decent access to charging infrastructure, meaning a Mach-E is still a viable vehicle to use IF it has the heating capacity we need.

I like that a heat pump is added as a concept (and yes, I also heat my house with an air-to water unit, and no, at -34C it is not effective but the electric backup heater takes care of that for those few days). But I am a little bit afraid that it does not mean an increase in total heater capacity, something the Mach-E really needs (on the AWD long range!) to be a better car in our conditions. In short, I want the heat pump to ADD heater capacity and would be fine with it being effective in moderate temperatures and take the range hit from resistive heating in extreme cold.

Yes, I understand these are kind of extreme conditions but maybe we would need the option from the 70's and 80's, to specify a certain "arctic heater" for those of us who are not sane enough to relocate to better climates...

 

[ChehRob]

My c2010 air sourced heat pump occasionally would function at 21 degrees F, my auxiliary heat was a propane stove/heater, also decorative. The electric heat strips seldom came into action.

Sponsored