HVAC expert James Smithell explains how Mitsubishi Hyper Heat systems differ from standard heat pumps and why they perform well in cold climates like New England. Hyper Heat models maintain full heating capacity down to around 5°F to -5°F, making them suitable for many homes without relying on fossil fuel heating. The conversation covers how the systems work in extreme cold, the role of defrost cycles, and when backup heat may still be recommended for older or drafty homes. Smithell also emphasizes the importance of proper Manual J load calculations and correct system sizing to ensure efficient performance and avoid issues like short cycling.
John Maher: Hi, I am John Maher and I’m here today with James Smithell of New England Heat Pump Company, a locally owned and family operated company with over 20 years of experience in the HBAC industry specializing in Mitsubishi heat pumps and ductless heating and cooling systems. Today we’re talking about Mitsubishi Hyper Heat. Welcome, Jimmy.
Jimmy Smithell: Thanks for having me on today, John.
What is the Mitsubishi Hyper Heat System?
John: Sure. Jimmy, tell me a little bit about what Mitsubishi Hyper Heat is and how it’s different from standard heat pump models.
Jimmy: Yeah, it’s really in the heating capabilities, right? So, there’s two different heat pumps made by Mitsubishi. There’s what we call standard heat and hyper heat. The real difference there is in the heating season, so the indoor units are all interchangeable. They’re all pretty much the same from hyper to standard. The outdoor design’s very similar. You wouldn’t notice a difference there. The compressor is definitely different. The compressors are a little bit bigger. We have a little bit more coil surface, so we have a little bit more area that we can disperse either AC or heat. The holy grail difference is going to be anything below, I would say 12, 15 degrees. It’s still going to heat hundred percent, so we’re getting a hundred percent heating capabilities out of that system at five degrees. The new sumo line minus five degrees, it’s still giving a hundred percent heat. So it’s really in the heating capabilities of that system.
How Low can a Standard Heat Pump System Go?
John: So, a standard heat pump system, you get down below, what did you say, 15 degrees or so? It’s going to start to lose its efficiency in terms of heat.
Jimmy: Yeah, so they still work. It doesn’t shut off. It just becomes very expensive to run and we’re losing a good percentage of the compressor. So if it’s a two port, 20,000 BTU compressor, standard heat, anything below 20 degrees, we’re going to start losing the actual BTU number on a scale. I think we lose about 60% of it down to five degrees. So, it’ll in fact still operate it just number one is running very expensive and number two, it’s not the proper size if we’re looking to heat that space.
How Can The Hyper Heat System Operate Below Zero Degrees?
John: So, talk a little bit more about those coldest days and how a Mitsubishi heat hyper heat system will maintain heat output below zero degrees.
Jimmy: Yeah, systems are amazing. I’ll tell you, I heat my own house a hundred percent, no backup heat with these systems, and I can vouch that I have three small children and we maintain 72 degrees throughout the whole winter on these systems. How it basically works is it’s called a scroll compressor, right? So, you got a picture, there’s a little compressor inside of these condensers that spin, and inside that scroll compressor spins a very high RPM. So, when we’re calling for heat at a very high load, that system’s going to ramp up what we call it turning up, and it’s able to do that because what we call flash injection. So, it’s coming in the backside with a little piece, a little tube of Freon to recool that compressor and allow it to run at such a high RPM and spin so fast. That’s what it’s doing. It’s using Freon on the back door to basically cool it off and cool those bearings off to have it last and create that heat.
John: And you said that it’s able to generate a hundred percent of the heat down to what, minus five degrees you said?
Jimmy: Yes. Yeah, so there’s a different lineup. So there’s what we call hyper heat, and then there’s the new lineup, which is called sumo heat. But regardless of those two, they’re both cold climate heat pumps made by Mitsubishi. The heating is amazing. The performance is hundred percent at either minus five or five degrees, so it’s still giving, if it’s a 36,000 BTU compressor, you’re still getting a true 36,000 BTU of heat at those ridiculously cold temperatures. It’s amazing in the heat pump industry, it really is amazing.
What Happens Below -13 Temperature?
John: And then what happens at that minus 13 degrees temperature? You’re losing a little bit of efficiency, but it’s still able to heat the house.
Jimmy: Yeah, we’re not shutting off, I mean, we’re still producing heat, we’re still producing heat very well. We’re just losing a little bit of percent of the actual size of the compressor. We’re not losing a lot, so you’re still going to get very good heat. We’re just going to struggle a little bit on the load. If we’re size at an 18,000 BTU unit inside, we’re probably going to run a little bit smaller than that in those, we don’t see it here in the Boston area much, but if it got that cold, you’re not going to have to move out of your house. We’re still going to heat that house. It might just be a little bit chilly.
How Often Does It Get Too Cold in the Boston Area?
John: And talk about that a little bit. You mentioned that in the Boston area and New England in general, we don’t see a lot of days where it gets below zero. It really even we’re in February here now in 2026 recording this, and we just had a cold spell where yeah, we had a couple of nights when it did get down to one degree or zero degrees or something like that, but that’s really quite rare and we really almost never see anything minus 10 or any kind of temperatures like that, right?
Jimmy: Yeah, no, it’s very rare. So our software that we use, it’s set to Boston Logan Temperature, so we use that as our benchmark and our software that we use is by code, we want to be heating at a 10-degree mark, so when we size a house, it’s in house. It’s basing off a 10 degree day, which if you look at a Boston Logan heat chart of that year, you hit it right on the head, John, there’s not a lot of days that we’re going to be below that temperature, if any. This year, like you just mentioned, we did have a very cold snap, but it’s very rare. This is not happened in many years. If you do look at that chart.
Are Backup Heat Systems Needed?
John: Do you still recommend having some sort of a backup heat system, and if so, what kinds make sense here in New England?
Jimmy: Yeah, really depends on the house. This is a big one. This is something that we talk about daily with homeowners owners. If it’s an old house that’s breezy and leaky, I would love to leave a secondary system in place for the first year just so we’re comfortable, right? This is a different type of heat and I have this conversation with my homeowners every day. Let’s just say we’re moving away from an old steam heat system that’s just a choo choo train, but that choo choo train works very well for that old 19th century house.
It’s just a different type of heat. We’re on the wall and we’re kind of doing heating in one location versus if you had heating in that house previously and we were on a few different walls with that hydronic system, I would love to leave backup heat in those older, bigger homes just so everybody’s comfortable through that first, we’d learn a lot the first cold week is what I tell my homeowners, right? Then if we’re, you’re comfortable, I’m comfortable, we’re good to go.
Problem areas are always going to be bathrooms, hallways and basements. These are the three heavy hitters that we look at when we transition these homes off of whatever type of fossil they have, either propane, oil, or resistance. How are we going to heat those spaces? We really have to dive into that. A lot of contractors will dodge that question or not even bring it up. We totally put it in front of the homeowner, and again, we just want to make sure everybody’s comfortable when we leave that house. The system will perform. We just talked about it, perform a hundred percent, five degrees minus five, some systems down to minus 10, but do we have it everywhere? Are we leaving bathrooms out, basements out or it’s hard. It’s a hard question. It’s not for every house, right? I would say if it’s a tight house, a new house, or been remodeled, yeah, we can heat that all day with heat pumps with no backup heat, but it’s a hard question. We do recommend leaving backup heat when we have to.
John: Okay. And it’s a conversation like you said, that you need to have with the homeowner. It really depends.
Jimmy: It’s different. Every house is different. The bigger older homes, I would tell you before walking into that house, I’d be way more comfortable leaving some type of secondary heat, just at least for the first year.
How to Size Hyper Heat Systems Correctly?
John: How do you size hyper heat correctly, so that comfortable for the homeowner without short cycling or inefficient running?
Jimmy: Yeah, that’s a big one. Manual J’s, you have to do a load calculation on the house. We have very advanced software that will come in. We’ll scan the house. It looks at things like your windows, your outside walls, your floors, your insulation. Is the roof below ceilings or do you have an attic? It looks at all these principles and then it’ll spit us out basically a blueprint with a load calculation. So, that’s the first piece. I would say that’s 50% of now we have the information that we need. Now we have to figure out equipment to match to that. Here’s where a lot of contractors we see daily basis go wrong with this.
They don’t select the equipment to fit not only the heat load, but we also have to match the cooling load out of one system. So, I would say start with a manual J and have somebody very knowledgeable if you’re going to be installing heat pumps in your house with the equipment side of things, what is the turndown ratios? Do we hit both my high heating load and my low cooling load? We really need that to fit to keep the system from short cycling.
What is a Defrost Cycle?
John: What is a defrost cycle and what should homeowners expect with that? Does it mean that they’re going to have any issues with any comfort issues when a system goes into a defrost cycle?
Jimmy: Yeah, so think about this system, right? It’s outside. So if we’re running this system on a cold January day that we just talked about here in New England, it’s got to breathe for a minute, right? It’s been running all this heat, it’s pulling in all this super, super cold air from outside. So, it’s pulling in that cold air. Let’s say it’s 10 degree day, it’s pulling in that air that’s outside and it’s pulling the heat out of it and sending it through its fans. It’s like a big radiator outside with a coil inside of it.
So, eventually that system has to cool itself down, and it’s called a defrost cycle, is what it’ll do. It really depends on the day and the temperature, how often. So, there’s no exact answer for me to tell you how many times a day it would do it on a super cold day. It would be a few times. It basically reverses itself. It’ll go into a cool mode, almost like a cool mode, and it’ll send the heat outside to the compressor instead of sending it through the indoor unit, and it’ll really just let that system defrost for a minute. It’s totally normal. The systems have to do it. If it does it, it’s operating correctly. It absolutely has to do that.
John: And so when it does that, then it’s not heating the house for that time period. But is it just a short time period and you wouldn’t even really notice it?
Jimmy: You wouldn’t. I mean, look, it’s going to give a little bit of cold breeze out of the indoor units, but it’s not going to make the house freezing. Typically. You wouldn’t notice your house being freezing because of it.
John: Alright, well that’s really great information Jimmy. Thanks again for speaking with me today.
Jimmy: Thank you, John. Take care.
John: And for more information, you can visit the New England Heat Pump Company website at neheatpumpco.com.
