I have been tracking Google’s NEST for awhile now. It’s the best example I know of a learning system for the home. The latest is …. it is still the best!
We spent more than a month trying five popular smart thermostats—testing the hardware, their accompanying mobile apps, and their integrations with various smart-home systems—and the third-generation Nest remains our pick. Five years after the Nest’s debut, a handful of bona fide competitors approach it in style and functionality, but the Nest Learning Thermostat remains the leader. It’s still the easiest, most intuitive thermostat we tested, offering the best combination of style and substance.
Last Updated: November 10, 2016
We’ve added our review of Ecobee’s new Ecobee3 Lite, and we’ve updated our thoughts on HomeKit integration following the launch of Apple’s Home app. We’ve also included details on Nest’s new Eco setting and color options, a brief look at the upcoming Lyric T5, and a clarification regarding the use of a C wire for the Emerson Sensi.
The Nest works well on its own or integrated with other smart-home products. Its software and apps are solid and elegant, too, and it does a really good job of keeping your home at a comfortable temperature with little to no input from you. Plus, if you want to change the temperature yourself, you can easily do so from your smartphone or computer, or with your voice via Google or an Amazon Echo. All of that means never having to get up from a cozy spot on the couch to mess with the thermostat. While the competition is catching up, none of the other devices we tested could match the Nest’s smarts. The expansion of the Works with Nest smart-home ecosystem and the introduction of Home/Away Assist have kept the Nest in the lead by fine-tuning those smart capabilities. The recent hardware update merely added a larger screen and a choice of clock interfaces, but the ongoing software improvements (which apply to all three generations of the product) have helped keep the Nest in its position as the frontrunner in this category without leaving its early adopters out in the cold.
Not as sleek or intuitive as the Nest, but it supports Apple’s HomeKit and uses stand-alone remote sensors to register temperature in different parts of a house, making it an option for large homes with weak HVAC systems.
The Ecobee3’s support for remote sensors makes it appealing if your thermostat isn’t in the best part of your house to measure the temperature. If you have a large, multistory house with a single-zone HVAC system, you can have big temperature differences between rooms. With Ecobee3’s add-on sensors (you get one with the unit and can add up to 32 more), the thermostat uses the sensors’ occupancy detectors to match the target temperature in occupied rooms, rather than just wherever the thermostat is installed. However, it doesn’t have the level of intelligence of the Nest, or that model’s retro cool look (which even the Honeywell Lyric takes a good stab at). Its black, rounded-rectangle design and touchscreen interface have a more modern feel, it looks a bit like someone mounted a smartphone app on your wall.
Ecobee’s new Lite model is a great budget option. It doesn’t have any occupancy sensors or remote temperature sensors, but it would work well for a smaller home invested in the Apple ecosystem.
For a cheaper smart thermostat with most of the important features of the more expensive models, we suggest the Ecobee3 Lite. This budget version of the Ecobee3 lacks the remote sensors and occupancy sensors of its predecessor but retains the programming and scheduling features, and like the main Ecobee3, it works with a variety of smart-home systems, including HomeKit, Alexa, SmartThings, Wink, and IFTTT. However, the lack of an occupancy sensor means you’ll have to manually revert it to its prescheduled state anytime you use Alexa, Siri, or any other integration to change its temperature.
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Table of contents
Why a smart thermostat?
Who this is for
The C-wire conundrum
How we picked and tested
Who else likes our pick
Flaws but not deal breakers
Potential privacy issues
The next best thing (for larger homes)
What to look forward to
Wrapping it up
Why a smart thermostat?
A smart thermostat isn’t just convenient: Used wisely, it can save energy (and money), and it offers the potential for some cool integrations. If you upgrade to any smart thermostat after years with a basic one, the first and most life-changing difference will be the ability to control it remotely, from your phone, on your tablet, or with your voice. No more getting up in the middle of the night to turn up the AC. No dashing back into the house to lower the heat before you go on errands (or vacation). No coming home to a sweltering apartment—you just fire up the AC when you’re 10 minutes away, or even better, have your thermostat turn itself on in anticipation of your arrival.
Technically, thermostats have been “smart” since the first time a manufacturer realized that such devices could be more than a mercury thermometer and a metal dial. For years, the Home Depots of the world were full of plastic rectangles that owed a lot to the digital clock: They’d let you dial in ideal heating and cooling temperatures, and maybe even set different temperatures for certain times of the day and particular days of the week.
The thermostat landscape changed with the introduction of the Nest in 2011 by Nest Labs, a company led by Tony Fadell, generally credited to be one of the major forces behind Apple’s iPod. (Google acquired Nest Labs in 2014; Fadell has since moved on to an advisory position at Alphabet, Google’s parent company.) The original Nest was a stylish metal-and-glass Wi-Fi–enabled device, with a bright color screen and integrated smartphone apps—in other words, a device that combined style and functionality in a way never before seen in the category.
The Nest got a lot of publicity, especially when you consider that it’s a thermostat. Within a few months, Nest Labs was slapped with a patent suit by Honeywell, maker of numerous competing thermostats.
But once the Nest was out there, it was hard to deny that the thermostat world had needed a kick in the pants. And five years later, not only have the traditional plastic beige rectangles gained Wi-Fi features and smartphone apps, but other companies have also entered the high-feature, high-design thermostat market, including the upstart Ecobee and the old standards Honeywell, Emerson, and Carrier.
The fact is, a cheap plastic thermostat with basic time programming—the kind people have had for two decades—will do a pretty good job of keeping your house at the right temperature without wasting a lot of money, so long as you put in the effort to program it and remember to shut it off. But that’s the thing: Most people don’t.
These new thermostats are smart because they spend time doing the thinking that most people just don’t do.
“The majority of people who have a programmable thermostat don’t program it, or maybe they program it once and never update it when things change,” said Bronson Shavitz, a Chicago-area contractor who has installed and serviced hundreds of heating and cooling systems over the years.
Smart thermostats spend time doing the thinking that most people just don’t do, turning themselves off when nobody’s home, targeting temperatures only in occupied rooms, and learning your household schedule through observation. Plus, with their sleek chassis and integrated smartphone apps, these thermostats are fun to use.
Nest Labs claims that a learning thermostat (well, its learning thermostat) saves enough energy to pay for itself in as little as two years.
Since the introduction of the Nest, energy companies have begun offering rebates and incentives for their customers to switch to a smart thermostat, and some have even developed their own devices and apps and now offer them for free or at a greatly reduced price to encourage customers to switch. Clearly, these devices provide a larger benefit than simple convenience. Because they can do a better job of scheduling the heating and cooling of your house than you can, they save money and energy.
Among the useful features of smart thermostats is the ability to work as part of a larger smart-home system and to keep developing even after you’ve purchased one. For example, many of the thermostats we tested now integrate with the Amazon Echo, a Wi-Fi–connected speaker that can control many smart-home devices. You can speak commands to Alexa, Echo’s personal assistant, to adjust your climate control. This function came to the thermostats via a software update, so a smart thermostat purchased last year has the same functionality as one bought yesterday.
These over-the-air software updates, while sometimes known to cause issues, are a key feature of smart devices. Shelling out $250 for a thermostat that has the potential to become better as it sits on your wall helps cushion some of the sticker shock. The Nest earns particularly high marks in this area, because whether you bought one in 2011 or 2016, you get the same advanced learning algorithms and smart integrations.
Additionally, all of the thermostats we tested work with one or more smart-home hubs such as SmartThings and Wink, or within a Web-enabled ecosystem like Amazon’s Alexa or IFTTT (If This Then That). The Nest also has its own developer program, Works with Nest, which integrates the company’s thermostat and other products directly with a long and growing list of devices including smart lights, appliances, locks, cars, shades, and garage door openers. This means you can add your thermostat to different smart scenarios and have it react to other actions in your home: It could set itself to Away mode and lock your Kevo smart door lock when you leave your house, for instance, or it could turn up the heat when your Chamberlain MyQ garage door opener activates. These ecosystems are continually growing, meaning the interactions your thermostat is capable of are growing as well (sometimes with the purchase of additional hardware).
With the release of the Home app for HomeKit, Apple’s smart-home unification plans have taken a bigger step toward fruition. While the devices are still limited (a hardware update is required for compatibility), you can now create scenes (linking devices together) and control them from outside the home on an iPad; previously you had to use a third-generation Apple TV. This change increases the number of people who will see HomeKit as a viable smart-home option. Even without an iPad permanently residing in your home, you can still talk to and operate HomeKit products using Siri on your iPhone or iPad while you are at home. The system works in the same way Alexa does, and it’s actually a little more pleasant to use than shouting across the room.
The Ecobee3, Ecobee 3 Lite and Honeywell Lyric (released January 2016) are all HomeKit compatible, and can communicate with other HomeKit devices to create scenes such as “I’m Home,” to trigger your thermostat to set to your desired temp and your HomeKit-compatible lights to come on.
Google now offers its own voice-activated speaker similar to Amazon’s Echo, the Google Home. The Home, which integrates with Nest as well as IFTTT, SmartThings, and Philips Hue, allows you to control your Nest thermostat via voice.
Who this is for
Get a smart thermostat if you’re interested in saving more energy and exerting more control over your home environment. If you like the prospect of turning on your heater on your way home from work, or having your home’s temperature adjust intelligently, a smart thermostat will suit you. And, well, these devices just look cooler than those plastic rectangles of old.
Get a smart thermostat if you’re interested in saving more energy and exerting more control over your home environment.
If you already have a smart thermostat, such as a first- or second-generation Nest, you don’t need to upgrade. And if you have a big, complex home-automation system that includes a thermostat, you may prefer the interoperability of your current setup to the intelligence and elegance of a Nest or similar thermostat.
If you don’t care much about slick design and attractive user interfaces, you can find cheaper thermostats (available from companies such as Honeywell) that offer Wi-Fi connectivity and some degree of scheduling flexibility. The hardware is dull and interfaces pedestrian, but they’ll do the job and save you a few bucks.
The devices we looked at are designed to be attached to existing heating and cooling systems. Most manufacturers now offer Wi-Fi thermostats of their own, and while they’re generally not as stylish as the models we looked at, they have the advantage of being designed specifically for that manufacturer’s equipment. That offers some serious benefits, including access to special features and a deep understanding of how specific equipment behaves that a more general thermostat can’t have.
The C-wire conundrum
One major caveat with all smart thermostats is the need for a C wire, or “common wire,” which supplies AC power from your furnace to connected devices such as thermostats. Smart thermostats are essentially small computers that require power to operate—even more so if you want to keep their screens illuminated all the time. If your heating and cooling system is equipped with a C wire, you won’t have any concerns about power. The problem is, common wires are not very common in houses.
In the absence of a C wire, both the Nest and the Honeywell Lyric can charge themselves by stealing power from other wires, but that can cause serious side effects, according to contractor Bronson Shavitz. He told us that old-school furnaces are generally resilient enough to provide power for devices such as the Nest and the Lyric, but that the high-tech circuit boards on newer models can be more prone to failure when they’re under stress from the tricks the Nest and Lyric use to charge themselves without a common wire.
Installing a C wire requires hiring an electrician and will add about $150 to your costs. The Ecobee3 includes an entire wiring kit to add a C wire if you don’t have one (for the previous version of this guide, reviewer Jason Snell spent about two hours rewiring his heater to accommodate the wiring kit). The Emerson Sensi is the only thermostat we tested that claims not to need a C wire, but it too draws power from whichever system is not in currently in use (for example, the heating system if you’re using the AC). This means that if you have a heat- or air-only system, you will need a C wire.
Note: If the power handling is not correct, the damage to your system can be significant. The expense of replacing a furnace or AC board, plus the cost of professional installation, will probably outweigh the convenience or energy savings of a smart thermostat. Nest addresses the power requirements of its thermostat, including whether a common wire is necessary, in detail on its website, so if you’re unsure whether your system is suited for it, check out this page for C wire information, as well as this page for system compatibility questions and this page for solutions to wiring problems.
If you have more than one zone in your HVAC system, you will need to purchase a separate smart thermostat for each zone. Currently, while all of the smart thermostats we tested are compatible with multizone systems, none can control more than one zone. Even though the Ecobee3 supports remote sensors, those feed only a single thermostat—so if you want more zones, you’ll still need separate thermostats, with their own sensors. However, the Ecobee3 is the only thermostat we tested that allows you to put more than one thermostat into a group so that you can program them to act identically, if you choose.
How we picked and tested
We put these five smart thermostats through their paces to bring you our top pick. Photo: Michael Hession
By eliminating proprietary and basic Wi-Fi–enabled thermostats, we ended up with six finalists: the third-generation Nest, Ecobee’s Ecobee3 and Ecobee3 Lite, Honeywell’s second-generation Lyric, Emerson’s Sensi Wi-Fi thermostat, and Carrier’s Cor. We installed each model ourselves and ran them for three to 10 days in routine operation. We did our testing in a 2,200-square-foot, two-story South Carolina home, running a two-zone HVAC system with an electric heat pump and forced air.
For each thermostat, our testing considered ease of installation and setup, ease of adjusting the temperature, processes for setting a schedule and using smartphone app features, multizone control capabilities, and smart-home interoperability.