Latest / Cool Talk with Hartzell's | Your HVAC Questions, Answered! / Modern Heat Pumps Thrive In Freezing Cold

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Modern Heat Pumps Thrive In Freezing Cold · Cool Talk with Hartzell's | Your HVAC Questions, Answered!

0:00
Picture this.
0:00
It's uh it's the middle of February.
0:02
It's a bone-chilling 18 degrees outside.
0:06
You're wrapped in a thick blanket, standing down in your basement, and your old reliable gas furnace has just totally given up the ghost.
0:13
Oh man, just the absolute worst timing.
0:16
Right.
0:16
It is completely dead, making that awful clicking sound that tells you zero heat is coming.
0:22
So naturally, you do what any of us would do.
0:25
You pull out your phone, shivering, and start searching for replacement options.
0:28
Because you do.
0:29
Yeah.
0:29
And you see an ad for a modern heat pump, but almost immediately the internet forums, your neighbor, your uncle, they all start screaming the exact same warning at you.
0:38
Do not get a heat pump.
0:40
They absolutely do not work in cold weather.
0:42
It is uh it's practically a universal reflex at this point.
0:46
That conventional wisdom is so deeply ingrained in our collective consciousness that people view heat pumps with this intense, almost visceral suspicion the second the thermometer dips below freezing.
0:56
And that visceral suspicion is exactly what our mission is in today's deep dive.
1:01
We are going to bust this pervasive 15-year-old internet myth wide open because as we're going to see, the advice you're getting online is dangerously out of date.
1:12
It really is.
1:13
So to get to the bottom of this, we're pulling from a massive stack of research today.
1:17
We're diving into a huge data set from the Oklahoma Mezzanet, covering minute-by-minute temperature data from 2010 all the way through 2025.
1:26
Aaron Powell Plus cold climate studies from the Department of Energy and the actual manufacturer performance curves from heavy hitters like Train, Mitsubishi, and Amana.
1:33
Right.
1:34
And we're grounding all of those lab numbers in the real-world 45-year field experience of Dave Hartzel.
1:39
He's a master HVAC installer who's been running these systems in central Oklahoma through decades of brutal winters.
1:46
Aaron Powell And you know what's fascinating here is that we're looking at a classic scenario where the engineering has just completely leaped forward, but human perception is stuck in the past.
1:54
Aaron Powell Yeah, stuck in like 2005.
1:57
Exactly.
1:58
Based on the data we were reviewing today, whether a modern heat pump works in the cold, I mean, it's no longer up for debate.
2:03
The technology handles it effortlessly.
2:06
The only actual question you need to be asking now is if the math makes sense for your specific house and your specific local utility rates.
2:15
Okay.
2:15
I'm gonna stop you right there because before we get into the weather data or the dollars and cents, I am stuck on something fundamental.
2:22
We need to talk about the physics.
2:24
Sure.
2:24
The physics usually trips people up.
2:26
Yeah, because I think this is where the mental block happens for most people, myself included.
2:31
How on earth does a machine pull hot air out of freezing cold air?
2:36
It sounds like you're trying to bend the laws of thermodynamics.
2:39
It does sound like magic, I'll give you that, until you strip it down to its basic components.
2:43
Yeah.
2:43
I mean the heat pump is literally just an air conditioner running in reverse.
2:46
It's just running backward.
2:47
Right.
2:48
It uses the same compressor, the same lines of refrigerant, and the same coils as your summer AC unit.
2:54
In the summer, your air conditioner absorbs heat from the air inside your living room and pumps it outside.
2:59
Makes sense.
3:00
But in the winter, a reversing valve shifts, and now it absorbs heat from the outdoor air and pumps it inside.
3:07
See, grabbing heat from a hot summer day makes total sense.
3:10
But grabbing heat from a freezing February morning, that just bends the mind.
3:15
I was thinking about this, and the best way I can visualize it is like wringing water out of a damp sponge that looks completely dry to the naked eye.
3:25
Oh, that's a really good way to think about it.
3:27
Aaron Powell Right, because even if the air feels freezing to you, there is still thermal energy, there is still heat trapped in that cold air.
3:33
But honestly, I still struggle with this.
3:35
How is there useful heat in 20 degree air?
3:38
That just feels scientifically wrong.
3:39
Aaron Ross Powell Right.
3:40
It feels wrong because we measure cold based on our human comfort level, which is usually around, you know, 70 degrees.
3:46
Yeah, 70 is nice.
3:47
But physics measures heat based on absolute zero, which is hundreds of degrees below zero.
3:53
To understand how a heat pump works, you have to look at the boiling point of the liquid doing the heavy lifting, the refrigerant circulating inside the outdoor coil.
4:01
Okay.
4:01
And what is the boiling point of that stuff?
4:03
The boiling point of modern refrigerants is an absolutely staggering minus 20 degrees Fahrenheit.
4:09
Minus 20, wow.
4:11
Yeah, think about what that actually means.
4:13
If the liquid in the coil boils at minus 20 degrees and the air blowing across that coil is 20 degrees above zero, that air is a full 40 degrees warmer than the refrigerant.
4:24
Oh wow.
4:25
Okay, so from the perspective of the chemical inside the machine, that freezing 20-degree winter day might as well be a tropical heat wave.
4:33
Precisely.
4:34
That 40-degree difference provides what engineers call a delta, a temperature difference.
4:39
As long as the air is warmer than the refrigerant, the refrigerant will absorb that thermal energy and boil into a gas.
4:46
Okay, but boiling refrigerant doesn't equal a warm living room.
4:49
I think this is the missing link for a lot of people.
4:51
How does that cold gas actually heat my house?
4:54
Well, that brings us to the most crucial step, which is the compressor.
4:57
Once that refrigerant boils into a gas, it travels through a pipe into the compressor unit.
5:02
Right, the big loud box outside.
5:04
Yeah, and the compressor takes that gas and violently squeezes it down into a tiny space.
5:10
When you compress a gas like that, you are forcing all those molecules to smash together at extremely high speeds.
5:17
Like um, like when you're pumping up a bicycle tire really fast and the bottom of the hand pump gets physically hot from all the pressure.
5:24
Yes, that is a perfect analogy.
5:26
The friction and pressure of squeezing that gas generates intense concentrated heat.
5:32
Okay, so it starts low level, but the squeezing makes it super hot.
5:35
Exactly.
5:36
So even though the gas absorbed relatively low-level heat from the cold outside air, the act of compressing it transforms it into a very high temperature gas.
5:46
That scorching hot gas then flows into the coil inside your ductwork, your blower fan pushes air across it, and that is what delivers a blast of warm air into your living room.
5:54
That makes a ton of sense.
5:55
And the colder it gets outside, the less total heat is available to grab, right?
5:59
Right.
5:59
But the system can easily grab useful effective heat and compress it all the way down to minus 10 degrees Fahrenheit.
6:04
Aaron Powell Okay, the physics totally makes sense now.
6:07
We are harvesting low-level heat, boiling a chemical, and squeezing it until it gets hot.
6:14
So if the laws of physics have always supported this process, where did the myth come from?
6:19
Like why do we all have that uncle who swears a heat pump left his family freezing back in 2004?
6:25
The short answer is that the bad reputation is completely earned, honestly, but it applies to outdated technology.
6:32
Oh, so the uncle isn't crazy, he just had an old unit.
6:34
Exactly.
6:35
Yeah.
6:35
If you installed a heat pump in the 1990s or the early 2000s, you were installing a single stage unit.
6:41
It had one speed fully on or fully off.
6:44
There was no nuance to it whatsoever.
6:45
Aaron Powell And before we get into why that was a problem, we should probably define a term that comes up constantly in the source material, which is BTUs.
6:52
Right, good idea.
6:53
So a BTU or British thermal unit is basically the amount of heat you get from burning one wooden kitchen match.
6:59
So when we talk about a furnace putting out thousands of BTUs, just imagine that many matches burning to heat your space.
7:06
That really helps visualize it perfectly.
7:08
And the fatal flaw of those old single-stage compressors was that when the outdoor temperature dropped, their capacity to move those BTUs plummeted right along with it.
7:18
How bad of a drop are we talking?
7:20
Well, let's say you had a standard three-ton heat pump back in 2002.
7:24
At a mild 47 degrees outside, it could pump out its full rating of 36,000 BTUs.
7:31
But when the temperature dropped to 17 degrees, that same unit choked.
7:36
Oh man.
7:36
Yeah.
7:37
Its output would drop to just 22,000 BTUs.
7:40
It physically could not move enough heat to keep up with the heat leaking out of the house.
7:44
And the house starts getting colder and colder.
7:46
So to make up that massive gap in heating power, those old systems had a built-in panic button, right?
7:52
They relied on electric strip resistance heat.
7:54
Exactly.
7:55
They basically just gave up.
7:56
So essentially when it got cold, you were abandoning the heat pump entirely and heating your whole house with a giant, wildly expensive toaster hidden inside your ductwork.
8:05
That is essentially what electric resistance heat is.
8:08
It's just passing raw electricity through metal coils until they glow orange hot, just like a space heater or a toaster.
8:16
The problem is the sheer inefficiency of it.
8:18
Using electric strip heat costs roughly three times as much per BTU as burning natural gas or moving heat with a compressor.
8:26
So picture what is happening to our homeowner in the year 2002.
8:30
It's a freezing morning, their heat pump has lost its capacity, the house gets cold, the thermostat panics, and the giant toaster kicks on.
8:38
And month later, they open an electric bill that makes them want to faint.
8:43
They were burning insanely expensive electric resistance heat instead of moving highly efficient refrigerant heat.
8:49
That experience, the lukewarm air blowing from the vents and the staggering utility bills, that is what cemented the bad reputation.
8:57
And if the technology had stopped there, the internet forums would be absolutely correct to warn you.
9:02
But the industry developed variable speed compressors and engineered much more capable cold weather refrigerants.
9:07
So how is a variable speed compressor different?
9:10
Instead of just turning on or off, a variable speed compressor acts like the gas pedal on your car.
9:16
As the temperature drops outside and the heat gets harder to extract, the compressor doesn't just give up.
9:21
It pushes harder.
9:22
Yeah, it physically revs up to a higher RPM to pump more refrigerant and compensate for the cold.
9:28
So it works harder so you don't have to use the toaster.
9:31
Exactly.
9:32
And if we look at the manufacturer curves from modern cold climate systems like the train variable speed units or the Mitsubishi hyperheat systems, the performance difference is staggering.
9:43
What do the numbers look like for those?
9:45
These modern units maintain 100% of their rated heating capacity all the way down to five degrees Fahrenheit.
9:52
Wait, 100%, down to five degrees.
9:54
Yep.
9:55
And even at minus five degrees, they are still pushing 70% of their capacity.
10:00
The backup strip heat almost never needs to kick on in a normal winter.
10:04
The machine is doing real, efficient refrigerant work, even in the bitter cold.
10:09
Okay, that sounds incredible on a manufacturer's spec sheet, but how does this actually apply to the listener's life?
10:16
Because I am looking at these numbers minus five degrees, and my first thought is how often are we actually hitting those extreme temperatures where even a modern unit might struggle?
10:25
Right.
10:25
We have to look at the real world application.
10:27
Exactly.
10:28
To answer that, we have to move out of the lab and look at hard climate data.
10:32
We're looking at the Oklahoma Mezzanet data, specifically for Kingfisher, Oklahoma, spanning a massive 15-year period from 2010 to 2025.
10:42
This is where we really have to separate the emotional fear of winter from statistical reality.
10:48
Human memory is completely biased.
10:50
Oh, totally.
10:51
We remember the brutal ice storms, but we forget the weeks of mild, boring weather.
10:55
Right.
10:55
When you actually look at the continuous mezzanet data over that 15-year span, the average January low in Kingfisher is 24 degrees.
11:04
The average high is 49.
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Now remember, a modern heat pump maintains full capacity down to five degrees.
11:10
Okay.
11:10
So on average, the unit isn't even breaking a sweat.
11:13
I have to push back here, though.
11:14
Averages are great, but people don't panic about averages.
11:17
They worry about the extremes.
11:19
I remember weeks where I felt like we never got above freezing.
11:23
What about the deep freezes?
11:24
Your point.
11:25
But the data covers every single minute of those deep freezes, including polar vortex events.
11:31
In an entire year, there are only about 180 hours where the temperature drops below 20 degrees.
11:38
Okay, 180 hours.
11:39
There are only about 35 hours a year below 10 degrees.
11:43
And here is the truly shocking number.
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There are only a mere eight hours a year on average where the temperature drops below zero.
11:50
Wait, eight hours.
11:52
Just eight hours.
11:53
I am having a hard time believing that.
11:54
Out of the entire winter, we are talking about roughly one single night of sleep where the temperature drops into the negative numbers.
12:00
The data does not lie.
12:02
That is the 15-year average.
12:04
And that brings us to a massive revelation for anyone considering this technology.
12:08
Which is.
12:08
For 99% of the winter, a modern heat pump runs entirely on the highly efficient refrigerant cycle.
12:14
It never needs the backup.
12:16
Yeah, that terrifying eight-hour window below zero where the heat pump might finally need a little help to keep up with the heat loss of your house.
12:24
You can easily cover that tiny fraction of the year with the electric strip backup or a gas furnace, and it might cost you a couple hundred dollars a year maximum.
12:31
That completely reframes the entire conversation.
12:34
We have spent 15 years terrified of an eight-hour window.
12:38
Pretty much.
12:39
So we've established the physics are sound, the technology handles the weather easily.
12:44
Now the ultimate question for you, the person listening, staring at that dying furnace, what does it actually cost to run?
12:51
Keeping warm is a priority, but keeping your bank account intact is usually the deciding factor.
12:56
Definitely.
12:57
To figure that out, we have to equalize the playing field.
13:00
We cannot just compare a random gas bill to a random electric bill because the units of measurement are totally different.
13:06
We need a standardized metric.
13:07
Right, apples to oranges.
13:09
Exactly.
13:09
So the source data breaks everything down into the cost per 1 million BTUs of heat delivered into your living room using projected 2026 Kingfisher utility rates.
13:19
Okay, let's run the wallet math.
13:21
Here is the cost to deliver one million BTUs of heat, which is about a week's work of heating in a typical house.
13:29
If you are heating with a standard 80% efficient natural gas furnace, it costs about$9.50.
13:36
Okay.
13:36
If you are heating with a modern heat pump, it costs about$12.
13:40
Got it.
13:41
If you are using that giant toaster, the electric strip resistance heat, it costs$28.
13:47
And if you are heating with propane, it is costing you a massive$30.
13:51
If we connect this to the bigger picture, the implications of those numbers are huge.
13:55
It creates what Dave Hartzell, our 45-year HVAC veteran, calls the no-brainer scenarios.
14:01
Who are the no-brainers?
14:02
Think about the homes relying entirely on electric strip heat paying$28 per million dolls, or homes out in the country relying on delivered propane at$30 per million dolls.
14:12
For them, making the switch to a heat pump at$12 is an absolute no-brainer.
14:17
You are literally slicing your heating bill in half.
14:19
If you were paying$600 a month for propane, you are now paying maybe$240 for the exact same amount of heat.
14:25
Easily a 50 to 60% reduction.
14:27
The operating cost savings are so dramatic in those scenarios that the upfront cost of installing the heat pump entirely pays for itself in just three to five years.
14:37
And after that, the money you save stays right in your pocket.
14:40
Exactly.
14:40
It is the strongest possible economic case for an HVAC upgrade.
14:45
But there is a nuance here, and I want to be really clear about this because the numbers we just read don't lie.
14:51
Natural gas still wins the math.
14:53
It is$9.50 for gas versus$12 for the heat pump.
14:58
That's right.
14:59
Natural gas is still currently the cheapest way to heat a home in central Oklahoma.
15:03
It is important to note that the gap between the two is steadily closing, though.
15:07
Because of utility rates changing.
15:08
Yeah, electric rates have been relatively stable, while natural gas rates and delivery fees have been trending upward.
15:13
But as of the 2026 projections, natural gas still holds the crown for raw operating cost.
15:19
So what does this all mean for someone who already has natural gas lines hooked up to their house?
15:23
If gas is cheaper, do they just ignore heat pumps entirely and buy another standard gas furnace?
15:29
Not at all.
15:30
This is where the industry has developed a really elegant middle ground solution called a dual fuel system.
15:36
A dual fuel system.
15:38
So like a hybrid approach, like a hybrid car.
15:40
That's exactly it.
15:41
In a dual fuel setup, you pair a high-efficiency electric heat pump with a traditional gas furnace.
15:47
The heat pump coil literally sits right on top of the gas furnace.
15:51
You have both systems sitting there ready to work.
15:54
So how does it know which one to use?
15:57
The real magic happens at the smart thermostat on your wall.
16:01
The system is programmed to run the ultra-efficient heat pump during all that mild winter weather we talked about.
16:07
Basically anytime it is above 30 or 35 degrees outside.
16:11
Which, as we learned from the Maisonette data, is the vast majority of the winter.
16:14
Exactly.
16:15
You are getting the incredible efficiency of moving heat with refrigerant for 90% of the season.
16:20
And then when that rare deep freeze hits and the temperature plunges down into the teens, the thermostat senses the drop, automatically shuts off the heat bump, and fires up the gas furnace.
16:32
Wow.
16:32
So you don't have to go flip a switch or anything.
16:34
Nope.
16:34
You do not have to do a thing.
16:36
The system handles the transition seamlessly.
16:39
So you really get the absolute best of both worlds.
16:42
You aren't stressing the heat pump at its lowest efficiency point, and you get that intense roaring blast of gas heat right when you need it most.
16:50
Exactly.
16:50
Now the trade-off is the upfront cost.
16:53
Installing a dual fuel system is generally going to run you about$1,500 to$3,000 more upfront than just swapping out a basic gas furnace because you are buying two separate heating technologies.
17:04
Right, you're paying for two engines.
17:06
Exactly.
17:06
But for homeowners who want the operational efficiency and carbon reduction of a heat pump without the psychological anxiety of giving up their gas backup, it is just the perfect fit.
17:16
This all brings us to a crucial reality check.
17:19
Dave Hartzall uses a fit matrix to determine if a house is actually ready for this technology.
17:25
Because even though modern heat pumps are amazing pieces of engineering, there are specific scenarios where installing one as your only heat source is just the wrong answer.
17:34
Yeah, the research is very clear about where a standalone heat pump struggles, and it usually has nothing to do with the equipment itself.
17:40
It's about the house.
17:42
It is entirely about the environment it is placed in.
17:45
For example, if you live in a large older house with a very leaky thermal envelope, meaning poor insulation, drafty windows, unsealed doors, a heat pump alone might leave you feeling chilly.
17:57
Not because it isn't producing heat, right.
17:59
Right, but because the house is leaking heat faster than the unit can replace it.
18:03
I was trying to think of a good way to describe this.
18:05
Putting a high-efficiency heat pump in a drafty, uninsulated house is like putting a Prius engine in a massive dump truck.
18:13
Oh, that's a good one.
18:14
The engine itself is an incredibly efficient marvel of modern engineering, but the vehicle is just too heavy and unaerodynamic to get any real mileage out of it.
18:23
Aaron Powell That is a very accurate way to look at it.
18:25
Another scenario where a standalone heat pump makes less sense is in the far northern Oklahoma counties, simply because they experience significantly more of those sub-20 degree hours than the central part of the state.
18:38
The statistical math shifts.
18:40
Makes sense.
18:40
And finally, if you have a home with a brand new, highly efficient natural gas furnace that is in perfect working order, there's no economic reason to rip it out and replace it with a heat pump right now.
18:52
Right.
18:52
Don't throw away a perfectly good furnace.
18:55
In those cases, you either stick with gas or you upgrade to the dual fuel option we just discussed when your AC unit eventually dies.
19:02
Let's bring all this home.
19:04
We have covered physics, 15 years of weather data, and the economics of keeping your house warm.
19:10
If you take one thing away from this deep dive, let it be this.
19:14
That 15-year-old internet myth you read on a forum at two in the morning, it is officially dead.
19:20
Completely busted.
19:21
Heat pumps absolutely unequivocally work in cold weather.
19:25
The technology has evolved from those single-stage toasters of the 1990s to variable speed marvels that can pull useful heat out of thin air at minus five degrees.
19:34
It's incredible progress.
19:36
The real metric you need to be considering isn't the thermometer outside your window.
19:40
It is your current fuel type and the insulation of your home.
19:43
Yeah, and the ultimate advice from all of these experts is to never ever guess.
19:47
Do not base a 15-year investment on a gut feeling or an angry internet comment.
19:52
Always demand a real mathematical load calculation and a customized operating cost comparison run specifically for your house, your square footage, and your local utility rates before you sign on the dotted line.
20:05
Absolutely.
20:06
Keep doing your research, run your own math, and we will catch you on the next deep dive.
20:10
You know, this whole thing raises an important question.
20:12
We noted earlier that the cost gap between electricity and natural gas is steadily closing.
20:17
Electricity prices are stabilizing while gas prices trend upward.
20:21
If that trajectory continues at its current pace, at what exact tipping point in the near future will dual fuel systems become entirely redundant?
20:30
Are we rapidly approaching a day where the existing natural gas infrastructure piped into millions of our homes becomes nothing more than an obsolete stranded asset?