July 2019 Update: I removed the list of products from this post as I don’t feel they give enough details on each product to make an informed decision. I hope the list of criteria is useful for making a purchasing decision.
On May 7th Google announced they are absorbing their Nest brand. One of the side effects will be the end of developer API access to Nest products.
I bought a Nest thermostat 6 years ago, before Google bought Nest. For quite a few years Nest has operated relatively independently, and I have been able to integrate the thermostat with iOS using homebridge. That seems to be a dead end this summer, so I am looking for a replacement.
There are many use cases that people have for smart thermostats, ranging from different types of heating and cooling to varied occupancy programs to integrations with other smart home products. I have combed some other thermostat reviews (in last section below) for the differentiating factors.
Common “C” Wire
Some thermostats require additional power to run, and a third wire running from your equipment to your thermostat mount is mandatory. Not everybody has this wire, and running the wire could be an expensive installation. Some thermostat kits contain a bridge device to run more power over the two wires, meaning you don’t need a “C” wire.
Do you use forced air? Heat pumps? Radiators? Baseboard heaters? Geothermal? Multi-stage heating? Is your heating method supported by your thermostat? There are options available for nearly everything, but most thermostats just cover the most common heating methods.
Additional wires are needed to run a Humidifier, Dehumidifier, or Ventilator. Lower-priced thermostats may not support these and you would then have to use an external controller.
Like a Humidifier/Dehumidifier, more wires are required. Most devices support cooling, and some support multi-stage cooling.
Some furnaces have a fan that can be run separate from heating, should you want to circulate air without heating/cooling. Usually requires additional wire.
Can run on batteries in addition or separately from the equipment wires. This is typically seen on lower-power thermostats that don’t use the Common wire.
HomeKit Compatible (or other platforms)
Is the thermostat natively compatible with Apple HomeKit? This means that a “bridge” device is not required to enable support, and that the device can be added to HomeKit using the native iOS Home app.
Please Note: Just because a thermostat says it is HomeKit compatible, doesn’t mean that it will use the local HomeKit API. As an example, the EcoBee will use the cloud HomeKit API and you cannot control it via HomeKit without an internet connection. This also means that if their cloud service is offline, you cannot control it via HomeKit either.
Alternatively, you may want to make sure it integrates with Amazon Alexa, Microsoft Cortana, IFTTT, or a self-hosted solution such as Home Assistant. Maybe you even want to run Google Home without Nest (perhaps to limit Google’s data collection?).
Does the thermostat include or support external temperature sensors, so you can heat/cool based on rooms away from the thermostat? Sensors should be cheaper than buying a second thermostat.
Filter Change Reminders
Can you set the app or device to remind you to change your air filter? Is the reminder adjusted based on usage? Some thermostats can also remind you to change your humidifier filters.
If you adjust the thermostat manually, will the thermostat adjust its default schedule? Is this mode targeted for 9-5 workers only? I noticed that the Nest thermostat would think I was away from home because I didn’t walk by it enough to trigger its motion sensor, and then notice the house getting pretty cool in the winter.
Some thermostats will use external sensors to also determine occupancy for learning schedules.
Is the interface awkward to use? Do buttons sometimes fail to work? Does the thermostat display anything when idle, or have a blank screen? If you have family or roommates that are not as technically interested, they may resent or be annoyed with an un-friendly interface.
Is the thermostat integrated with a smart speaker/microphone system, like Google Home or Amazon Alexa? You may even be looking for a device that specifically does not do this, or at least lets you disable the “feature.”
Does the thermostat have cloud integration so you can remotely control it outside your home Wi-Fi? Is the cloud service reliable?
Energy Usage Reports
Is there data collection to tell you how much you used your heating/cooling? Is the data in an open format that you can download?
MSRP and Rebates
The cost of the device may vary considerably depending on where in the world you live. A device that might be 30% cheaper than the competition may be the same price in your country; in that case, which one you should buy may be different. Your locality may also offer rebates to discount certain brands for an energy savings program.
- Wirecutter: The Best Smart Thermostat
- Wirecutter: The Best Smart Thermostat for HomeKit
- Apple: List of HomeKit Accessories
- Consumer Reports: Nest Learning Thermostat vs. Honeywell Lyric T5
- Yahoo: Nest vs. Ecobee: Which one is the better smart thermostat?