My existing system which I converted from an oil boiler 11 years ago uses a 22kw air source heat pump running through a buffer store and consists of radiators with some ground floor under floor heating. The heat loss according to the heat geek easy calculator is around 8kw. DHW is via solar PV and inline water heaters + input from the ASHP if needed. The house has most rooms as zones with individual thermostats. The normal system running temp is 42-45C.
I would like to change the ASHP for a modern inverter type with weather compensation and run direct without the buffer over the summer if it ever arrives.
I previously bought a full monitor kit as I would like see how the system performs. I was originally going to monitor the existing ASHP but I think it would rather change the existing ASHP and modify the system before installing.
Question is what heat pump to choose as most seem very similar on specs but not on prices!
I’ve installed all my own plumbing and electrics (most of which requires notification now) and I’ve been looking into this myself. I like to engineer things correctly and install everything safely, so take everything that I say with the appropriate amount of salt.
Vaillant’s Arotherm range of heat pumps seem the easiest for DIYers to buy and install. There’s a 9kW version. See “Heat Geeks” and “Urban Plumbers” on YouTube for useful information.
Choose a fairly large unvented hot water cylinder for hot water efficiency (Heat Geek recently did a few videos on this). Ideally, all of your primary pipework needs to be 22mm (perhaps some at 28mm) and you’ll want to remove as many bends as possible for efficiency. I’m guessing that your heat emitters are probably already large enough (I had to change almost all of my radiators). All the manufacturers recommend buffers, low loss headers, etc but I’d plumb everything direct, use the pump in the monoblock, and see how that works before trying those things. If there are performance problems, I’d suggest upgrading the pipework and straightening it before adding buffers and low loss headers. Simpler systems are better.
I have a 12kW Gen6 Samsung, just coming up to a year old, so can’t comment on long term reliability, but it has been fine since installation
On my short list when starting out were Daikin and Mitsubishi (been in the HVAC business a long time, kit should be reliable), Vaillant (it uses eBus which I hacked 20 years ago for boiler control, so could easily connect into HEMs), Hitachi (good reputation but not so easily available) and Samsung (reasons as above).
Thanks for the info—all useful stuff. I see that the Samsung is now G7, assuming that its minor improvements from G6 and good point about the external pump which I already have.
A lot of the data sheets dont give the min output for the unit, which I find surprising…unless I’ve missed it somewhere. Also I’m pretty clueless about the various interfaces like Modbus, at the moment I dont see why I need anything like that apart from the controller…perhaps I will as I learn more!
Is mainly a heat pump change as I aready have the unvented cyl installed and hot water system working.
The changes have been prompted by looking at how things seem to have progressed since I intalled mine but the biggest influences to date are the postings by urban plumber and heatgeek.
The chinese ASHP I’m using now has Hitachi scroll compressors and has been faily reliable apart from changing all the power capacitors in the motor circuits, its kept us warm for 9 years. The oil boiler is still in place and I’ve fitted motorised ball valves so that I can change the entire system over to the oil boiler at the flick of a switch in the event that the ASHP cannot cope but Ive never really used it so in the next upgrade they will go along with the buffer.
Other things I forgot to mention in my list of Samsung advantages
Gen 6 uses R32 as the working fluid, Gen 7 uses R290 (propane), a more environmentally friendly refrigerant. No doubt R32 will get more expensive with the move to propane and CO2. The compressor and motor are in a hermetically sealed canister, like a fridge, so assuming no bad pipework, it shouldn’t need a recharge in its’ working life. By the time it does, then replacement rather than repair will be the better alternative. I see in the first Gen 7 devices they incorporated the pump and stuff inside the heat-pump (G7 integrated), but they seem to now also make a version without, like the G6, probably by popular demand.
You may well be happy with the controls provided, but it is always useful to have a known way out if there is some show stopper you find after installation. I believe HA (Home Assistant) has a Modbus interface so that could provide you with alternative control with minimal software skills needed.
Not straightforward to answer - some vendors (Samsung included) fit the same compressor to a range of heat pump sizes, and since the onset of compressor surge will be one of the factors that sets unit turndown, any vendor-supplied minimum output must be interpreted accordingly.
I have an 8kW Samsung HTQ (call it Gen 6.5 if you like) but this has the same compressor as the 12kW and 14kW versions. Samsumg UK Tech Helpline told me that the minimum heat output for my unit is “about 4kW” or 50% of nameplate.
I’ve verified this on several test runs - when the inverter frequency drops below 20Hz (in response to weather compensator or roomstat algorithm demands), the controller stops the compressor. This corresponds to a heat duty of a little below 4kW. (The nameplate 8kW is a bit conservative except at really cold source conditions, and 9.5kW is generally achievable, so 20/50*9.5 = 3.8kW which is what I see when the compressor stops.)
But this limiting heat duty will also apply to the larger units. So turndown should indeed be expressed in terms of heat duty (in kW) rather than as a fraction or percentage.
Sarah
Edit: BTW I am very happy with my Samsung (1 year old today) and would strongly recommend…
Many thanks for the replies—thought I had missed the min figure somewhere also perhaps is not so important as its working into a buffer rather than direct to rads as per heatgeek and urban plumber utube video’s.
The Samsung Gen 7 12kw seems to be fine for what I want and is around the size of the existing 22kw so an easy swap as pipes and elec already exist. Looked at more utube and doesnt look too bad to set up.
Planning a start later in the “summer” now that the solar PV is coping easily with the DHW
Sprsun/Cool Energy. A very capable machine, built on a complete Carel refrigeration controller platform.
The 9kW will run down to 4kW at the bottom end. Very good weather comp, fully configurable PID controller, built in PWM pump and flow sensor.
DIYd my install last September and have been very pleased with the performance this past winter.
I’ve got it running open loop (no buffer, llh or zoning) on pure weather comp. Although I’ve recently fitted a thermostat to act as a hi-limit stop now we’re into warmer weather.
EDIT: They do three versions - this one is the 9kW and uses R410a, it’s not in stock at the moment but the almost identical version that uses R32 and has EVI, and gives 10kW is in stock. They also do an R290 unit that’s 9kW, although it is pricey compared to the competition.
Yes its an interesting option and the spec looks good and under consideration. Price is good but also found a Samsung Gen7 12kw for not much more at £. We are similar with rads upstairs and UF down + rads. Our UF is from 25 years ago and it’s rubber pipe, still intact but not very good for conductivity and originally ran at 65-70C so added some rads downstairs and big improvement overall at lower temp.
Think I’ve seen the none linear waether described as altering the curve on some videos but not sure.
Have you got full monitoring as well?
The best heat pump depends on where you live. All of them are efficient, electric, all-in-one heating and cooling systems. But some heat pumps are built to thrive in homes with central ductwork and long stretches of hot, humid weather to contend with. Others are better suited to regions with sub-zero temperatures and houses without ductwork.
"Not every heat pump is right for every situation," says Chad Scherfler, an Area Sales Manager for Mitsubishi Electric Trane. "But there is a right heat pump for any situation." We've cataloged all the air-to-air heat pumps made by every major manufacturer and found that for most homes, there are plenty of heat pumps that would work.
Every HVAC contractor will recommend a heat pump (or two) when they give you a quote for an installation, so you don't have to figure this out on your own. If you have an idea of what could work for your house, though, that knowledge will protect you from bad advice offered by shoddy contractors. It could also help you spot a great deal on a high-performance heat pump from a lesser-known manufacturer.
But some contractors just eyeball it (the ol' "Manual E"), or are so sloppy with their load calculations that they might as well be guessing. If you suspect you’re getting not-so-careful advice from an installer, here’s what you’ll need to know about your home to make an informed decision.
Start by finding your climate zone on the IECC Climate Zone Map. It divides the US into 8 temperature zones based on how much heating and cooling they tend to need in an average year (measured in degree days). It also defines 3 different humidity zones: Humid, dry, and marine (basically lots of rain, but dry summers).
In the context of heat pumps, the climate zone gives you an idea of how closely you need to consider the cold-weather credentials and dehumidification abilities. Higher numbers mean you need to pay more attention to the heating specs. In humid zones, you should pay attention to dehumidification.
Even within these climate zones, there can be big differences in the temperature extremes. Boston rarely drops below 12 degrees Fahrenheit, while you should expect Chicago to get as cold as minus-3 Fahrenheit—even though they're both in Zone 5A. A heat pump that could work year-round in Boston would have a tough time during Chicago's bitter winters.
The best thing to do is look up your town's design temperatures. The American HVAC industry goes by the 1% cooling and 99% heating temps published by ASHRAE (an engineering guild), based on historical weather data. So about 99% of the hours per year, temperatures in your town will be higher than the heating design temperature, or lower than the cooling design temperature. Those have proven to be reliable cutoffs to design a system that can keep you safe and comfortable, even when temperatures occasionally shoot beyond those extremes.
The latest ASHRAE numbers from are hidden behind a paywall, but Energy Star published a county-by-county database based on the ASHRAE handbook, and that should be accurate enough for you to form an educated opinion. The NEEP Cold Climate Heat Pump Database also has a tool that can help you find your closest design temperature. Some load calculation software (see the next section) will often incorporate the most accurate design temperatures based on your zip code, too.
These numbers, measured in BTU, tell you how much heating or cooling a heat pump needs to crank out to keep up with the weather during those very cold and very hot design temperature days that we covered in the previous section. The industry-standard way to do this load calculation is the Manual J procedure.
It can be tough to perform a totally accurate load calc on your own, but you can probably get a decent ballpark estimate. As we covered in our guide to heat pump sizing, with a bit of patience and some free software like CoolCalc, you can get close enough to the truth.
If you see a bunch of air vents around your house, your home has ductwork. (Most homes in the US do.) When you get a heat pump, you'll most likely connect it to those ducts.
If you don't have ducts, or they don't connect to certain rooms, it's usually easiest to go with ductless heat pumps. You'll mount indoor air handlers onto your walls or into the ceilings in every room that needs it. (You could also add new ductwork, though that’s only practical if you have space in an unfinished attic or basement.)
Plenty of the top-performing heat pumps can be either ducted or ductless systems or even a mix of both at the same time. However some models only work with the central ductwork, and a few are ductless only.
(Some heat pumps can work with hot-water radiators, too. They're common in Europe, though it can be tough to find an installer in the US, and they're not very good at cooling. We haven't spent much time looking into this category yet.)
When a heat pump is a match for your house and climate, it's incredibly comfortable and energy efficient—probably a big improvement over whatever HVAC system it's replacing. So the more you can get things dialed in, the better you'll feel at home, and the more money you'll save on your energy bills.
Goto ZKN to know more.
Ideally, you want a heat pump with enough capacity to meet your home's heating and cooling loads (all measured in BTU) but at your local design temperatures. That second part is the tricky bit because the rated capacity is often different from the actual capacity in cold weather.
The good news is that there's usually a heat pump that can meet all these criteria, even in parts of the country where it gets pretty cold. (It's probably going to be an inverter heat pump—more on those below).
Cooling is straightforward: What you see on the spec sheet is basically what you get in real-world cooling performance. If a heat pump says that it’s 48,000 BTU (4 tons), it’ll give you that full capacity even when it’s really, really hot outside—well above 100 Fahrenheit. Top-quality installers might give special consideration to dehumidifying (aka latent heat), and that can matter in some edge cases.
Heating is trickier because the real-world heating capacity can be much different from the spec sheet's rating in cold weather. Certain 48,000 BTU heat pumps will actually produce all 48,000 BTU at 5 Fahrenheit. Other so-called 48,000-BTU heat pumps might only crank out 36,000 or 24,000 BTU when it gets that cold out, and some just don't work. Here are some real-world examples, taken from the NEEP database of cold-climate heat pumps.
Some models keep working even below 0 degrees F. Plenty of heat pumps are rated to work in temperatures as low as minus-22 degrees F, and there are plenty of testimonials from people who have found that they can still work fine during brief cold snaps down to minus-30 degrees F. It all depends! You’ll need to dig into the specs a little to make sure you find something that can meet your heating load at your home's design temperature. (And it's okay to pick a heat pump that works in colder weather than your local design temperature.)
What if you can't find a heat pump that perfectly matches your home's heating load? According to the ACCA Manual S procedure, it's fine to pick a heat pump with anywhere from 10% less to 30% more capacity than your loads, if it's a variable-speed model. (Here's a good summary of the guidelines.) Oversizing the capacity any more than that is a big mistake, though. It leads to worse comfort, higher energy bills, and possibly a shorter lifespan for the heat pump itself. Every credible HVAC and energy efficiency organization warns against this, even with variable-speed heat pumps. Undersizing isn't ideal either, but that rarely happens.
In the coldest parts of the US—climate zones 7 and 8 for sure—you'll probably need another heating source beyond a heat pump to handle the coldest parts of the year. We've heard about homes in these zones that do fine with heat pumps alone, though we get the impression that those buildings tend to have excellent insulation and air sealing.
In most other parts of the US, a hybrid system is never strictly necessary. You can purchase a heat pump rated to keep your house comfortable all by itself, with no backup system, if that's something you want. That said, some backup heat—whether that's auxiliary heat from electric strip heaters or a hybrid dual-fuel setup that includes fossil-fuel equipment—is often the most practical way to get a heat pump into your home for the least amount of money, and still goes a long way toward shrinking your home's overall energy use.
A major defining trait of a modern heat pump is the number of stages or speeds—that is, the possible combinations of compressor and fan settings. There are a bunch of nuances, but you can break it down into three sub-types, as influential building scientist Allison A. Bailes, Ph.D. puts it,
Inverter heat pumps are the most comfortable and energy-efficient type in any climate. They often cost more than other types of heat pumps and HVAC systems, but that’s not always true thanks to big incentives from governments and utility companies. The technology is worth it, and you should consider buying one.
With single-stage HVAC (including furnaces, central ACs, heat pumps, and others), the system is either a) all the way on and blasting out heating or cooling, or b) turned off completely. It’s designed to keep your home comfortable on the coldest and hottest few days of the year.
This one-speed method can be an awkward compromise during the other 360 days because it tends to heat or cool your house too fast. As the equipment switches on and off multiple times throughout the day, you'll feel the temperatures swing up and down by a few degrees. (It's usually more obvious in some rooms than others). The humidity is never quite under control, either—think of how sticky your house can get in the spring or fall when it's not hot enough to have the AC cranking all day. (HVAC pro and electrification advocate Nate Adams explains it well in this video, starting around the 12:30 mark.)
But inverter-driven heat pumps offer a better way. They can blast out heating and cooling as needed in both kinds of extreme weather, but also keep you more comfortable on more days of the year because they algorithmically adjust their output based on the weather and the conditions inside your home, delivering steady, comfortable climate control pretty much all the time. (This Old House has a good video explainer.)
These models constantly shift their settings in the background to offset small changes in indoor and outdoor temperatures. Scherfler, the manager at Mitsubishi, told us that their inverter heat pumps have thousands of distinct settings. From what we understand, many other brands also have inverter heat pumps with hundreds or thousands of settings, too, though some have fewer.
Inverters can't cover up every crime against HVAC: You still need a heat pump that's the right size for your house, decent ductwork (or a smart ductless design), and a competent installation. When all of those pieces come together correctly, inverter heat pumps are a big step up in comfort from basic equipment.
One reason inverter heat pumps save energy is—somewhat counterintuitively—because they run nearly constantly. (At least when they're designed and installed correctly). The most inefficient part of an AC or heat pump's cycle is the first 10 minutes after the system clunks to life, as the compressor gets churning and the refrigerant starts to reach its target temperature. Every time this happens, the system uses electricity without doing any heating, cooling, or dehumidifying. Single-stage heat pumps typically start and stop a few times per day, and that waste adds up over an entire year. Inverter heat pumps avoid this problem because they rarely shut down. Instead, they turn down and run at a slower speed.
Those low, steady speeds also boost the overall energy efficiency. Experts tend to use the gas mileage analogy: It's the same reason your car gets better mileage running at 55 mph all day than if you drove the same distance by constantly revving to 110 mph and then slamming the brakes. Inverter heat pumps aim to be continually driving at a reasonable speed. As this Department of Energy report on HVAC sizing puts it: "To reach peak operational efficiency and effectiveness, a heating and cooling system should run for as long as possible to meet the loads."
Many credible experts (including many DOE researchers, see the previous link) also think that inverter heat pumps should last longer than single-stage equipment. We haven't seen any data to support this, but the theory has some logic behind it: One-speed equipment takes more abuse because it cycles on and off multiple times every day—jolting to life, blasting along at top speed, then grinding to a halt. Inverter-driven models, on the other hand, tend to start up slowly and run at a moderate speed most of the time. During some parts of the year, they can go days or weeks without turning off. (The counter-argument is that inverter heat pumps are much more complex, so more things can go wrong during installation and everyday operation, and it can be tougher to maintain them properly.)
Inverter heat pumps aren't perfect. Even with hundreds or thousands of settings, they still have a minimum speed—usually 25 to 35 percent of the advertised capacity. That means they'll cycle on and off during very mild weather when your home's heating and cooling loads are low. (More on this in the section on turndown ratios below.) The good news is that if it's a well-designed system, you'll barely notice because the weather is pretty pleasant anyway.
If one of the lower-end inverter models would be a good fit for your house and climate (it'd likely have to be a centrally ducted setup in a warm- or mixed-weather region) you could actually end up saving money on the cost of installation compared to a single-stage heat pump or even a basic central AC and mid-efficiency furnace. The sticker price for the inverter heat pump will almost always be higher, but it would probably qualify for a $2,000 federal tax credit that the one-speed heat pump or AC / furnace combo wouldn't get. It could get some state or local incentives, too. That's all before any potential savings on your utility bills.
In colder climates and bigger homes converting to multi-zone ductless setups, a heat pump will typically cost more than your other HVAC options (unless you live somewhere with a big rebate program, and the contractors actually pass along that rebate rather than inflating their prices). You might earn back the difference through savings on your utility bills if you're converting away from oil, propane, or electric-resistance heating, or you have a boatload of solar panels to power the heat pump.
Finally, you might have to ditch your favorite smart thermostat (like the Nest), because they often can't control an inverter heat pump as it's meant to be controlled. Those models with hundreds or thousands of individual settings rely on their manufacturer's proprietary thermostats to facilitate those small adjustments, based on data coming from the indoor and outdoor units. Most third-party smart thermostats can't do that, and that defeats the whole purpose of buying an inverter heat pump. There are some exceptions, so check with the manufacturer or your contractor.
Millions of people in parts of the US with warm weather and cheap electricity already rely on a single-stage heat pump. For many homes in the South, it's been the most affordable type of HVAC system for decades, and plenty of people are comfortable enough with the setup. In places where it only occasionally drops below 30 or 35 Fahrenheit, they switch to a simple auxiliary electric strip heater for backup. It's not the most efficient way to make heat, but it's cheap to install and won't run very often, so it's been a practical workaround for occasional cold snaps.
The argument for single-stage heat pumps has always been weak beyond climate zone 4 because you'd need to rely on backup heat for long stretches of the winter. They could sort of make sense as a replacement for an air conditioner because both appliances work the same way in cooling mode. As the argument goes, if you're going to replace an old AC anyway, you might as well make it a heat pump and take advantage of the cheap, clean heat for spring and fall—even if you keep an old combustion furnace or boiler to run all winter. (Some advocates have even proposed that ACs should be phased out in favor of heat pumps altogether.)
But in warm and cold climates alike, new incentives have tipped the scales in favor of inverter heat pumps. One-speed heat pumps aren't efficient enough to qualify for rebates or tax credits, so once those discounts are applied, plenty of inverter heat pumps work out to be cheaper. Any of those models can crank out enough heat for warm climates, with no backup needed, and slightly lower energy bills as a result (and often less demand on the grid, if that's something you think about). The lowest-cost inverter models usually need some backup heat in colder parts of the country once the temperature drops below 15 degrees F or so, but it won't have to run as often as it would with a single-stage model.
Beyond those fundamental specs, the best way to make yourself more comfortable and save energy is to make sure your home meets some common-sense standards for insulation and air sealing. If you're using a ducted heat pump, you need decent ductwork, too. Seriously, take care of this stuff! These steps can slash your energy use by 30 percent or more in some cases, enough to cover the cost of the work through utility savings in just a couple of years.
It's also crucial to work with an installer who knows what they’re doing. Even if you're sure that you have a good system design, the attention to detail and craftsmanship that goes into the actual hands-on installation is also very important.
The secret to the best performance here is having a low minimum capacity, relative to the maximum output. Sometimes this spec is called the turndown ratio. The wider the gap between the lowest and highest capacities, the more leeway the system has to work well across the widest range of temperatures. Remember, inverter heat pumps want to run as often as possible at the lowest, steadiest setting they can manage. This is how they hold steady temperatures, and it helps them eke out better efficiency. No heat pump will run 100 percent of the time, but the closer you get, the better.
I'll use a real house and some real heating loads as an example: A pretty-good Manual J assessment done in CoolCalc (free load calculation software) says that a single-family bungalow near Boston needs 36,700 BTU of heat, at the local design temperature of 6 degrees F. At 40 degrees F (closer to the average temperature throughout the cold season) the heating load is only 17,500 BTU. And at 55 degrees F, it’s only 9,000 BTU.
So a 36,000 BTU cold-climate heat pump with a 4:1 turndown ratio (minimum speed 9,000 BTU, or 25% of the rated load) is pretty close to perfect for that house. It could run steadily and efficiently for almost the entire heating season. It'd likely still cycle on and off a bit during the mildest parts of the heating season (high 50s / low 60s outdoors). Would you notice any difference in comfort? Probably not with such fair weather. You could chase a wider turndown ratio, but it'd be a small payoff.
Multi-zone mini-splits: The other case where turndown ratio can make a big difference is with multi-zone systems—multiple indoor air handlers attached to a single outdoor unit. This is usually the most practical way to set up an entire house with ductless mini-splits, for example. But it poses a unique design challenge directly related to turndown ratios.
"A big turndown is incredibly important for mini-splits," says Peter Freedman, an HVAC designer from Massachusetts who has worked with these systems since the mid-s. A wider turndown range can help offset (or cover up) some of the compromises and shortcuts that almost always happen in a multi-zone mini-split design.
An ideal multi-zone system is one where the outdoor unit is the right size for the load of the entire building, and then each individual indoor unit is the right size for its room, and the total capacity across the indoor and outdoor units aligns perfectly. In the real world, that's hard to pull off because indoor units only come in so many sizes.
A little bit of oversizing is usually inevitable in most rooms, and it can sometimes mean that the outdoor unit ends up being a little bit oversized as well. On a room-by-room basis, it's not such a big deal. But across multiple zones, the combined effect of that oversizing can add up, as Freedman described it to us.
The system's minimum and maximum capacity are dictated by the outdoor unit. So if all the indoor units combined ask for less heating or cooling than the outdoor unit's minimum setting, the outdoor unit will force extra capacity through the indoor heads anyway, which leads to shorter cycles—and shorter cycles make your home feel less comfortable while using more energy. A wider turndown ratio can smooth over these awkward compromises, in a wider range of conditions.
Turndown isn't the only important spec, and you should weigh it against other factors. The actual efficiency (best measured by the coefficient of performance, aka COP) matters more than the general rule of thumb that low turndown equals energy savings. Some models with big turndown ratios aren't especially efficient at their low settings, it turns out. Better reliability could also be worth more than a higher turndown ratio, though that's tough to gauge, as we'll cover shortly.
The conventional wisdom is that inverter heat pumps are excellent for dehumidification because they run constantly, even when it's not super hot outside. As long as they're turned on, they usually pull some moisture out of the air (as long as your home isn't too dry already).
The truth is a little more nuanced than that, and it has to do with the speed of dehumidification. With a typical single-stage heat pump or central AC unit, about 25% of the energy used in a cooling cycle goes toward dehumidifying the air (known in the industry as latent heat), and the other 75% goes toward cooling the air (sensible heat). That's plenty of dehumidification even for a humid climate. After about 15 minutes, it'll bring the humidity down to a comfortable level. The downside is that once the system shuts off, the humidity will often rise faster than the air temperatures, so you're left feeling a little clammy in between cooling cycles.
Some inverter heat pumps remove moisture much more slowly, with only 10% or 5% or in extreme cases only 1% of the total energy working toward dehumidification. This happens because the indoor coil in an inverter model usually doesn't get as cold as the coil in a single-speed model—so when the fan blows air across the coil to cool it off, the humidity in the air doesn't condense into water as readily. It's the same reason why a cold can of soda "sweats" on a hot day, while a can at room temperature does not.
You probably don't need to worry about this, though. As long as the heat pump is the right size for your house, most models will knock the humidity down to a comfortable level during the summer. Once it gets going, it's actually better at keeping the humidity under control better than a traditional heat pump or AC. And the warm coil saves a bunch of energy, too.
One potential workaround: Look for a heat pump with a Dry mode, which dehumidifies the air without dropping the room temps. Plenty of mini-splits have one. If you live somewhere with a relatively short humid-but-not-hot season, this can come in handy.
Or you could look into a separate dehumidifier. That could be as simple as a portable dehumidifier (preferably with the Energy Star badge and a pump so that you don't need to remember to empty the water bucket). Or it could be a whole-house dehumidifier of some kind.
These are the industry-standard specs that measure a heat pump's energy efficiency. SEER is for cooling, and HSPF is for heating. (The industry actually switched to SEER2 and HSPF2 as of , which are purported to reflect real-world conditions better—we're using the terms interchangeably here.)
Higher SEER and HSPF ratings generally lead to lower energy costs, but most industry insiders we've talked to think that they're not an accurate rating scheme for inverter heat pumps, particularly cold-climate heat pumps. The testing methodology was developed decades ago for single-speed equipment and hasn't changed enough to capture the efficiency of efficient inverter-driven models.
It's probably not worth getting too caught up in minor differences in SEER and HSPF. All inverter heat pumps are very efficient compared to whatever HVAC system you're replacing, says Edward Louie, a Building Energy Efficiency Research Engineer at the Department of Energy's Pacific Northwest National Laboratory. "It's like asking, 'Should I buy the old Prius that gets 45 miles to the gallon, or the new Prius that gets 53 miles to the gallon?' That's a measurable difference. But if your current vehicle gets 10 miles to the gallon, then it doesn't matter what you choose, it's going to be way better."
A heat pump is usually a five-figure investment and protects your family and home from extreme weather, so of course you'd want one that's reliable. Unfortunately, there's not a ton of great data out there on what the most reliable heat pump brands actually are.
Consumer Reports has the best reliability info (paywalled), based on an extensive and long-running annual survey of their subscribers. It's highly trustworthy, and there's info about some major manufacturers of inverter heat pumps. But the data is incomplete. Several major brands are excluded from the rankings, and (as I learned during a stint working there) the share of data collected from people who live in cold-weather states was statistically insignificant up through .
So what can you do? You could listen to your contractor. Pros avoid working with equipment prone to repairs (at least early in the equipment's lifespan) because they're on the hook for the work under warranty. That said, they're still making decisions based on their personal experiences, which in the grand scheme of things is still a pretty limited view.
You could also look at the manufacturer's warranties as a sign of how much the installer stands behind their product. Most brands cover most parts for at least 7 years, but others extend the coverage out to 10 or even 12 years, and some will cover the cost of labor on certain parts.
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