Editor’s note: Originally published June 2018. Reviewed and updated November 2026. Some models mentioned here may have been updated or discontinued since; check current availability and specifications before buying.
Quick answer
- Both the 2nd and 3rd generation Nest Learning Thermostats learn your routine in about a week and can auto-schedule to save energy.
- The 3rd generation adds a larger, higher-resolution screen, longer-range motion sensing and sensor-assisted Home/Away detection.
- The 2nd generation costs less and keeps most of the same core features.
- Neither generation supported separate remote room sensors at the time of writing.
- If you’re buying new, the 3rd generation is the better choice; if you already own a 2nd gen and are happy with it, upgrading is hard to justify.
The Nest Learning Thermostat is a smart thermostat that is not only programmable but learns your routine. Both the 2nd and 3rd generation models combine your initial settings with built-in sensors to keep you comfortable and cut energy use. The 3rd generation improves on the 2nd in almost every area, but none of the changes are dramatic.
This comparison is based on the features Nest described for each model at the time of writing, not on hands-on testing.
Who a learning thermostat suits
A smart thermostat that adjusts itself can save a lot of hassle if you:
- constantly adjust the thermostat by hand,
- try to save energy by changing the temperature when you leave, or
- like to sleep at a very different temperature than you spend the day at.
Both Nest generations pair with an app that lets you view and change the temperature remotely and track your energy history over time. Both also work with many popular smart home devices and platforms. For a wider look at what to check before buying, see our thermostat buying guide.
Nest 2nd vs 3rd generation at a glance
| Feature | Nest 2nd generation | Nest 3rd generation |
|---|---|---|
| Learns your routine | Yes, in about a week | Yes, in about a week |
| Display | Smaller, lower resolution | Larger, higher resolution, readable across the room |
| Motion sensing | Lights up when you walk by | Longer-range far-field sensor |
| Away detection | Auto-Away after about 2 hours with no motion; more prone to false triggers | Home/Away Assist using phone location plus sensors and other Nest products |
| Energy tracking | App history and Nest Leaf | App history and Nest Leaf |
| Remote room sensors | No | No (at the time of writing) |
| Price | Lower | Higher |
Nest 3rd Generation review
Easy installation has been a Nest focus from the start. The 3rd generation comes with what you need to mount it, including a screwdriver, and its base has a built-in level so the thermostat sits straight on the wall.
Setup is a series of questions about your home and heating; the thermostat behaves differently for a house versus a business and for different fuel types such as propane or electric. Then you connect it to Wi-Fi. It works with most 24-volt heating and cooling systems and can run without a C wire by charging its battery through the heating and cooling wires.
Compared with the 2nd generation, the screen is larger with a higher resolution, and the far-field sensor detects motion from further away. After about a week of adjustments, you can turn on Auto-Schedule, which combines the settings you’ve made with the thermostat’s own sensors and algorithms to build an energy-saving schedule. You can keep refining it over time.
Home/Away Assist
Many smart thermostats rely on geofencing, which tracks your phone and can make mistakes if your signal is unreliable. The Nest 3rd generation adds its own sensors to help decide whether anyone is home, and if you have other Nest products it uses them too.
Smart home compatibility and security
At the time of writing, the Nest 3rd generation worked with most smart home platforms but not Samsung SmartThings or Apple HomeKit, so check Nest’s current list of supported devices. Tight integration lets you do things like control it with Alexa or have your lights dim when the thermostat switches to Away. Nest also added two-factor authentication to its accounts for better security.
Sensors and limits
The thermostat has sensors for temperature, humidity, near- and far-field activity and ambient light, so it knows a lot about the room it’s in. What it lacked at the time of writing was support for remote sensors in other rooms. Most homes won’t miss that, but if your home is drafty, has several levels or has rooms with very different temperatures, a system with multiple room sensors may suit you better; see our ecobee vs Nest comparison.
It came in white, black, copper and stainless steel finishes.
Pros
- Improvements in most areas over the 2nd generation
- Larger, sharper screen
- Longer-range motion sensing
- Home/Away Assist combines phone location with sensors
- Works without a C wire on most 24V systems
Cons
- Costs more than the 2nd generation
- No remote room sensors
- Did not work with every smart home platform (no SmartThings or HomeKit at the time of writing)
Nest 2nd Generation review
The Nest 2nd generation has many of the same features as the 3rd generation. It isn’t quite as good at everything, but it still does its job well and costs less. At the time of writing, Nest continued to support it with app and software updates.
The most noticeable difference is the display: the 2nd gen screen is smaller and lower resolution, so it is harder to read from across the room. It lights up when you walk by, which makes it easy to check and doubles as a subtle night light. The background glows blue when cooling and orange when heating; when idle, it shows white text on black, so you can tell what it’s doing at a glance.
It learns your routine just as well, in about a week. If you keep making the same change, it learns to anticipate it. The app shows your energy history, and a green leaf icon appears on the thermostat when you’re saving energy.
Auto-Away switches to an energy-saving temperature when it hasn’t detected anyone walking past for more than two hours. It learns if you usually leave at certain times, but it is more likely than the 3rd generation to mistake simple inactivity for an empty house.
Pros
- Costs less than the 3rd generation
- Same learning and auto-scheduling ability
- Energy history in the app and Nest Leaf on the device
- Color-coded display shows heating or cooling at a glance
Cons
- Smaller, lower-resolution screen
- Auto-Away is more likely to misfire
- Generally does not perform quite as well as the newer model
Which Nest should you choose?
- Buying your first smart thermostat: the 3rd generation’s sharper screen, better motion sensing and Home/Away Assist make it the better pick.
- Already own a 2nd gen and happy with it: the improvements probably aren’t worth the cost of upgrading.
- Want to spend less: the 2nd generation keeps the core learning features at a lower price, if you can still find it.
- Need room-by-room sensing: look for a system that supports remote sensors; our ecobee3 review covers one alternative to Nest.
Bottom line
Both Nest generations deliver the main benefit of a learning thermostat: less fiddling and lower energy use. The 3rd generation is the refined version, with a better screen and smarter away detection, while the 2nd generation remains a capable, cheaper option. If you just want a basic schedule for less, see our best thermostats under $50.
FAQ
How long does a Nest take to learn my schedule?
About a week of adjustments for both the 2nd and 3rd generation, after which you can turn on Auto-Schedule.
Does the Nest need a C wire?
The 3rd generation can work without a C wire on most 24-volt systems by charging its battery through the heating and cooling wires.
Does the Nest support remote room sensors?
Neither the 2nd nor the 3rd generation supported remote room sensors at the time of writing.
