A homeowner adjusts a smart thermostat connected to a mini-split system on the wall of her home

Smart thermostats are all the rage these days, boasting convenience, high-tech good looks, and even money-saving features.

Mini-split heat pump systems are also more popular than ever today. They are cornering the market as a popular choice for heating the entire home, or for providing heating and cooling for house add-ons and garage conversions.

The big question is whether these two innovative technologies play nicely together already or whether they are too new for their respective design teams to have gotten around to building features to allow them to integrate.

Well, how just compatible are these two systems?

Do Smart Thermostats Work With Mini-Splits?

Smart thermostats such as Nest and ecobee help you manage the temperature in your home via a smartphone app. While it is technically possible to connect mini-splits to a third-party climate-control system, it is not recommended because it thwarts the mini-split’s intelligent, energy-saving features.

Thus, smart thermostats are not very compatible with mini-split heat pumps. Still, similar solutions for remote access and scheduling are available for mini-splits in the form of smart Wi-Fi controllers.

However, there is an alternative that makes the key benefits of smart thermostats available for mini splits, including remote control over the internet and easy scheduling.

Keep reading if you want to know how to take advantage of this alternative.

If you are interested in whether a smart thermostat can control an ERV or HRV, you can read about that in our article here.

What Is a Smart Thermostat?

Smart thermostats are internet-enabled devices that help you manage your heating system more conveniently and efficiently through modern technology to adapt better to the patterns of a household. For example, they can automatically switch off the heating when nobody is home.

A smart thermostat on the wall in our second net-zero home

Standard programmable thermostats allow you to set periods of the day when the heating should be on and times when it should be off. However, if you are very disciplined about this and have a reasonably structured routine, you might not benefit much from installing a smart thermostat.

But, if you’re like most people, things pop up from time to time, changing your schedule at the last minute. Or maybe you don’t want to spend the time programming your thermostat to fit your schedule.

If that’s the case, then a smart thermostat could be for you.

What Does a Smart Thermostat Do?

Smart thermostats like the Nest have a learning feature that notices what temperatures you prefer at different times of the day and adapts automatically. You don’t need to worry about setting the temperature manually.

One of the particularly clever things that a smart thermostat can do is notice when you are out and even turn on the HVAC system when it sees you are on your way home.

A common practice for a standard programmable thermostat is to set it so that your home is cooler while you are out at work during the day. Then, shortly before you arrive home, the thermostat switches the heating on so that your home is nice and warm for your return.

The problem with this is that sometimes you have to stay later at work, there are delays during your commute because of traffic jams, etc. But your heating still comes on at the scheduled time, heating the house unnecessarily, wasting energy and money.

With a smart thermostat, you can log in via your smartphone from your desk and make sure the HVAC doesn’t come on while you finish off the report your boss has asked you to submit before you go home.

A homeowner adjusts the settings on their smart thermostat from their smartphone.

Some intelligent thermostat models use a geolocation feature to detect when you’re not home to avoid heating or cooling the house while you’re out.

The more advanced models even notice when you are on your way home so that they can turn on just in time to get things cozy for your return.

The most notable features of smart thermostats are as follows (not all models offer all these features, but this gives an idea of what is available).

  • Large, prominent temperature displays – gone are the days of squinting at a small, feint LCD display from across the room.
  • Remote control over the internet from your smartphone – change your home’s temperature any time, anywhere. Useful to stop your pipes from freezing while you’re away or to ensure your pets are comfortable while you’re out.
  • Create heating and cooling schedules using the app on your phone or tablet – no more awkward fiddling about creating plans using tiny buttons on an old-fashioned thermostat.
  • Save money on your energy bills – this is a big attraction for many people.
  • Household pattern learning – this feature automatically learns when you are in and when you are out, so you don’t have to program the thermostat manually.
  • Weather tracking – automatically turns the temperature up or down according to local weather conditions.
  • Energy profiles – some models use information about your home, such as size, which climate zone you are in, etc., to tailor the setup to your circumstances and simplify operation.
  • Tracking energy use – get an on-demand update on your energy consumption, complete with graphs, trends, and advice on where you could save energy.
  • Voice control – compatible with Alexa and Google Assistant, many smart thermostats can be used with voice commands.
  • Motion detection – automatically detect when people are at home and active using motion sensors, which helps tailor the learned schedule to your needs.

As you can see, smart thermostats offer many features that help you to save money on your energy bills. If you would like to learn about more ways to save money on heating, ventilation, and air conditioning, read our roundup of ways to do it here.

Smart Thermostat Compatibility

The issue of compatibility of your HVAC system with smart thermostats like Nest, ecobee, Honeywell, and the like is a complex matter. If you are in any doubt at all, we strongly recommend seeking the advice of a professional.

How to Check Whether Your Existing System is Compatible 

If you have an existing forced-air system with a wall-mounted thermostat, you can look at your wiring to determine compatibility with an intelligent thermostat.

Each smart thermostat manufacturer has compatibility guides that walk you through checking whether their thermostat will work with your current HVAC system.

A homeowner using the Nest Compatibility Checker to determine compatability with their mini-split system
Courtesy of Colton Crump DIY

The problem is that unless you’re a reasonably savvy DIYer or, in some situations, an HVAC professional, you could struggle to follow the guidelines completely. And even if you do, you might not be 100% confident you’ve arrived at the correct answer.

If you try to follow any of these guides, you’ll quickly see what I mean. Most of them have you turn off the existing furnace as a first step. I have to say that my mom would fall at this first hurdle, and she’s not alone.

If you know where the off switch is for your existing system (even if you have to turn it off at the breaker board), you’re on to the next step.

Some manufacturers ask you to look for a standard wire or c-wire, which provides the power for the thermostat. This involves removing the cover plate for your existing unit, which might need a screwdriver (again, I don’t think my mom owns such a thing).

Once you’ve got your thermostat off the wall, you need to check the wiring to ensure none of it is high voltage because most smart thermostats are low voltage and won’t be compatible.

The telltale signs of high voltage are labels that say 110, 120, or 240V or have L1/L2 written on them. Some even have the classic high voltage sign with the lightning bolt in a warning triangle—that’s much harder to overlook.

Next, you must read the labels close to the terminals the existing wires are plugged into, select those labels in the manufacturer’s online tool, and hit “submit.” Chances are, you’ll then be asked to contact support and provide photos of your existing wiring.

That’s quite an involved process for the average homeowner, so we recommend getting professional advice. But if you’re up for the challenge or already an expert, we wish you the best of luck!

The Problem With Using a Smart Thermostat With a Mini-Split

Installing a Nest or ecobee smart thermostat with your mini-split heat pump might seem reasonable. After all, the benefits seem like they are worth the effort.

There’s just one snag, and it’s not talked about much.

Smart thermostats are designed primarily for use with central air systems, which can be either on or off. But, they are not compatible with mini-splits because they will undo some intelligent energy-saving features the system already has, such as precise control of the compressor speed.

Two mini-split compressor units outside a home in snowy conditions
The exterior compressor component of a ductless mini-split

Central air can heat and cool a room in less than half an hour, but your furnace will have to run often to maintain that warmer temperature. Having a smart thermostat tell your system when it can shut off and allow the room to cool down because you’re not home can save a significant amount of money throughout a heating season.

But when it comes to modern mini-splits, the story is different.

Mini-splits with modern inverter-driven compressors are bristling with their own smart technology. They can intelligently adjust the heating and cooling output to keep the temperature at the desired level.

They achieve this by fine-tuning the compressor’s speed to precisely what is required, making them very efficient.

Hooking these intelligent devices up to a separate thermostat, no matter how “smart,” is likely to cause problems with efficiency and might even reduce their lifespan due to turning them on and off frequently, which they are not designed for.

Adapters for Using Mini-Splits With Smart Thermostats

Adapters are available to allow some mini-splits to work with certain smart thermostats.

This sounds great in principle, but the models we have seen do not get good reviews. Also, the problems mentioned above, like undoing most performance optimizations that come built into a modern mini-split, are an issue that crops up in the reviews section of online vendors.

One reviewer’s experience highlights the pitfalls of trying to force compatibility using third-party adapters. A user named Zeke said the following of a model he had tried with a Mitsubishi mini-split.

“Works, but beware if you have a heat pump. This adapter WILL work with heat pumps however I strongly recommend against it as it will undo most performance optimizations. That’s because this [thermostat adapter interface] can’t send IR data and some other data to the outside unit. What ends up happening is that any call to heat will trigger the backup electric resistance, turning your nice efficient heat pump into a toaster.”

In fact, the product description for this adapter states that it “works with conventional systems, NOT heat pump control.” Not even the manufacturer is willing to recommend its use with a heat pump!

So, we’ve established that you can’t use a standard smart thermostat with a mini-split heat pump. But what if I told you that you could have a similar experience using an intelligent Wi-Fi controller?

Smart Wi-Fi Controllers for Mini-Splits

A smart Wi-Fi mini-split controller works differently from a traditional thermostat. It is really an upgrade to the LCD remote that comes standard with a mini-split and controls your system’s air handler units using infrared signals, just like the original remote does.

However, once you’ve set up the controller, you can access it via your phone over the internet, giving you many of the same convenient features as a Nest or similar smart thermostat.

It might not provide complete control of all the features of your mini-split, such as dry mode or fan-only mode, but it will allow you to program schedules for heating and cooling as well as give you remote access.

There are several manufacturers of these Wi-Fi mini-split controllers. They are marketed as smart thermostats, but they aren’t technically thermostats.

They control the mini-split settings using infrared signals the same way the remote does, with the thermostat itself being part of the original system.

The following brands manufacture “smart thermostats” for mini-splits.

  • Mysa
  • Cielo
  • Honeywell
  • Sensibo

Convenience and the ability to control your heating and cooling remotely over the internet are the key selling points for all these systems.

There is some variability in terms of warranty and the range of the infrared units, so worth considering which are compatible with your home setting before you buy.

A summary of essential features is provided in the table below.

Comparison of Key Features of Wi-Fi Mini-Split Controllers (Smart Thermostats)


Mysa Smart ThermostatCielo BreezeHoneywell D6Sensibo SkyFlair Puck
Free ShippingAcross N AmericaThe US OnlyAcross N AmericaThe US OnlyThe US Only (order must be over $229)
Thermostat Display and ControlYesYesYesNoYes
Range30 feet6-12 feet30 feet20 feet30 feet
Free Access to All App FeaturesYesYesYesYesYes
Warranty2 years1 year5 years1 year1 year
Integration with Other Smart Home ProductsApple Homekit, Alexa, Google HomeAlexa, Google HomeAlexa, Google Home, SmartThingsAlexa, Google Home, IFTTTAlexa, Google Assistant

These mini-split smart thermostats should be compatible with most systems that use a full state LCD screen display with target temperature, fan speed, and mode settings. 

Manufacturers include Mitsubishi, LG, Daikin, and several other popular mini-split companies. We recommend you use the thermostat manufacturers’ compatibility checkers or refer to their website before you buy.

A quick phone call to their support department would help avoid any doubt.

Summary

Smart thermostats offer a convenient way to control your compatible HVAC system. They allow you to manage your system remotely over the internet, create schedules using an app on your phone, and can even save you money on your energy bills.

Mini-splits are not truly compatible with third-party smart thermostats because they have their own intelligent control software that optimizes efficiency and performance.

Therefore, adding a separate thermostat will undermine the onboard control systems and make the mini-split work less efficiently.

However, Wi-Fi controllers are available that offer the convenience of remote access from any location via the internet. These systems also allow scheduling, and smart home integrations like Alexa and Google Assistant, without compromising the optimal performance of the mini-split system.

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