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For most buyers choosing between used or refurbished units, the 3rd-generation Nest Learning Thermostat is the better choice. It supports more HVAC configurations, Nest Temperature Sensors, humidifiers and dehumidifiers, and certain domestic hot-water systems. The Nest Thermostat E makes sense mainly when it is substantially cheaper and your home has a simple, compatible heating-and-cooling system.
There is an important qualification: neither model is a current Google retail product in the US. Google lists the 3rd-generation Learning Thermostat as no longer sold and the Nest E as no longer available. If the price of either older model approaches that of a current thermostat, buying new is usually the safer decision.
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| Feature | Nest Learning Thermostat (3rd gen) | Nest Thermostat E |
|---|---|---|
| Google retail status | No longer sold | No longer available |
| Google’s approximate HVAC coverage | 95% of systems | 85% of systems |
| Automatic learning schedule | Yes | Yes |
| Nest Temperature Sensor | Supported | Supported |
| Humidifier/dehumidifier control | Supported | Not listed as supported by Google |
| Separate domestic hot-water tank control | Supported on applicable systems | Not supported |
| Setup app | Nest app | Nest app |
| Display | Larger illuminated display | Smaller translucent display |
| Controls | Metal ring with turn-and-press control | White plastic ring |
| C wire | Often works without one, but system-dependent | Often works without one, but system-dependent |
Google’s compatibility percentages are broad manufacturer estimates, not guarantees. Your wiring, HVAC equipment, stages, controls and accessories determine whether a particular installation will work.
What are these models?
The Nest Learning Thermostat (3rd generation) is the older premium Nest model. It has a metal ring, a larger illuminated screen, physical turn-and-press controls and the learning features associated with the Nest brand.
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- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills[2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
The Nest Thermostat E is the simplified, lower-cost model. Its translucent white display and white plastic ring are designed to blend into the wall. It still offers remote control, Eco Temperatures, occupancy sensing, automatic scheduling and Auto-Schedule, but it supports fewer HVAC configurations and has a simpler interface.
Do not confuse either thermostat with the 2020 Nest Thermostat. That is a different budget model controlled through the Google Home app. It uses Quick Schedule rather than the older models’ learning-based Auto-Schedule and does not support the Nest Temperature Sensor.
Neither model is a current Google purchase
Google’s US comparison page identifies the 3rd-generation Learning Thermostat as “no longer sold,” while the Nest E product page says “no longer available” (Google thermostat comparison; Nest E specifications).
Third-party sellers may still have new-old-stock, used or refurbished units. Condition and protection vary considerably, so check the return policy, warranty, included mounting hardware and whether the thermostat has been removed from the previous owner’s account. A discontinued product can still function, but future support, replacement parts and warranty coverage are less certain than with a current model.
Compatibility should come before price
The 3rd-generation Learning Thermostat is generally the stronger option for complicated systems. Google estimates compatibility with approximately 95% of systems, compared with approximately 85% for the Nest E. The figures are not a substitute for checking the actual installation.
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- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills [2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
Before buying, use Google’s official compatibility checker and photograph the existing thermostat wiring with HVAC power switched off. Record terminal labels—not just wire colors—and confirm the equipment at the control board if necessary.
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Pay particular attention to:
- Heat pumps, reversing-valve settings and auxiliary or emergency heat.
- Dual-fuel systems.
- Multiple heating or cooling stages.
- Boilers, radiant systems and hot-water controls.
- Zone controllers.
- Humidifiers, dehumidifiers and ventilation equipment.
- Whether a C wire is installed and connected at the HVAC control board.
- Whether the system is a proprietary communicating system rather than standard 24-volt equipment.
C-wire and power requirements
Both models are designed to operate without a C wire in many homes, but “no C wire required” is not universal. Heating-only systems, cooling-only systems, heat pumps and zone-controlled systems can be especially sensitive to power requirements.
Symptoms of an installation that is not receiving stable power can include low-power warnings, repeated reboots, the thermostat going offline and HVAC short-cycling. Google’s Nest Power Connector may provide an alternative to installing a new C wire; Google listed it at $24.99 when checked in August 2026. It is not a universal fix, so confirm compatibility first.
Turn off HVAC power at the breaker or service switch before touching wiring. If you have dual fuel, zone controls, unusual wiring or expensive HVAC equipment, professional installation is the prudent choice.
Feature differences that matter
Scheduling and learning
Both the 3rd-generation Learning Thermostat and Nest E support Auto-Schedule. They can learn preferred temperatures and build a schedule, while still allowing manual scheduling. The 3rd gen provides the more premium interface and controls, but the E is not merely a basic programmable thermostat.
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- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills[2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
Learning does not guarantee a lower energy bill. Results depend on your existing settings, occupancy, insulation, climate, HVAC efficiency and whether you accept or override schedule changes. Google’s “up to 31%” savings claim should be treated as a manufacturer claim, not a promised result for every home.
Remote temperature sensors
Both models support the Nest Temperature Sensor, sold separately. A sensor can let the thermostat use the temperature in another room during a schedule period, which can help when a bedroom or office is consistently warmer or colder than the thermostat location.
It does not create independent HVAC zones or heat and cool that room by itself. One thermostat still controls the equipment.
Humidifiers and dehumidifiers
This is a decisive advantage for the 3rd-generation Learning Thermostat. Google lists support for humidifier and dehumidifier systems for that model, while its comparison information does not list those functions for the Nest E. Do not choose the E merely because its basic heating and cooling wires appear to match; accessory equipment can make the installation incompatible.
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In applicable systems and regions, the 3rd-generation Learning Thermostat can control a separate domestic hot-water tank with on/off control. The Nest E cannot control a separate hot-water tank and may require the existing programmer to remain in place. This is particularly relevant in some UK and European installations, not a universal feature of US HVAC systems. See Google’s guidance on hot-water compatibility and programmer arrangements.
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- Programmable smart thermostat that learns your schedule and the temperatures you like and programs itself to help you save energy and stay comfortable
- Home/Away Assist automatically adjusts itself to an Eco Temperature after you leave, so you don’t heat or cool an empty home; remote control lets you change the temperature from anywhere on your phone, laptop, or tablet[1]
- With Energy History, just check your phone to see how much energy you used and why, or use Quick View on the display to reach Energy History, settings, or your schedule; the Nest Leaf appears when you choose a temperature that saves energy
- Smart thermostat with HVAC monitoring, which looks out for your heating and cooling systems; sends an alert if something doesn’t seem right, along with helpful reminders to make maintenance easier[2]
- The Nest Learning Thermostat works with the Nest Temperature Sensor (sold separately) to help make sure a certain room is the exact temperature you want it to be
Display and physical controls
The 3rd gen has the more substantial design: a metal ring, larger illuminated display and turn-and-press interaction. The Nest E uses a white plastic ring and a smaller, lower-resolution translucent display that is less visually prominent.
That is a difference in visibility, materials and controls—not evidence that one measures temperature more accurately. There is no basis here for claiming superior sensing accuracy or reliability.
Apps and smart-home expectations
The 3rd gen and Nest E use the Nest app for setup and control. The 2020 Nest Thermostat uses the Google Home app. An older Nest thermostat therefore will not necessarily appear or behave like a current Google Home product.
Google continues to publish documentation and software information for the 3rd gen and Nest E. A documented April 7, 2025 update included bug fixes and a new fan-timer function for those models in North America (Nest software update history). Google’s October 25, 2025 end-of-support announcement applied to the first- and second-generation Learning Thermostats, not these two models. That distinction does not provide a guaranteed future support lifespan.
Nest Learning Thermostat (3rd gen): strengths and weaknesses
Choose it when:
- You need humidifier or dehumidifier control.
- You want to use a Nest Temperature Sensor.
- Your system has more heating and cooling stages within its compatibility limits.
- You value the larger display and physical dial.
- You need separate hot-water tank control in a supported regional installation.
- The used-price premium over the Nest E is small.
Watch out for:
- Discontinued retail availability and uncertain used-market warranty coverage.
- Power issues on installations without a C wire.
- Higher prices that may bring it too close to a current thermostat.
- Assuming “95% compatibility” means your specific system is guaranteed to work.
Nest Thermostat E: strengths and weaknesses
Choose it when:
- It is substantially cheaper than a comparable 3rd-generation unit.
- You have a straightforward, compatible 24-volt furnace, air-conditioner or heat-pump system.
- You do not need humidifier/dehumidifier control or separate hot-water control.
- You do not need remote temperature sensing.
- You prefer a thermostat that blends into the wall.
Google’s specifications list the E for one stage of heating and cooling, plus a second stage of either heating or cooling, and for several system types including gas, electric, forced-air, heat-pump, radiant, oil, hot-water, solar and geothermal systems subject to wiring and configuration limits. Google specifically recommends professional installation for dual-fuel systems (Nest E technical specifications).
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Connectivity : Wi-Fi - 802.11b/g/n 2.4 GHz, 802.11a/n 5 GHz Wi-Fi., Wireless interconnect : Bluetooth Low Energy Please refer to the product description section below for all applicable legal disclaimers.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home. Lock feature: No
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
Which one should you buy?
| Your situation | Best direction |
|---|---|
| Buying new from Google | Choose a current Nest model instead of either discontinued model. |
| Both used units cost nearly the same | Choose the 3rd-generation Learning Thermostat. |
| Simple furnace/AC and the E is much cheaper | Choose the Nest E, after compatibility verification. |
| Uneven rooms and need for a remote sensor | Choose either older model; the 2020 Nest Thermostat is not suitable for this requirement. |
| Humidifier or dehumidifier | Choose the 3rd gen, subject to wiring verification. |
| Separate domestic hot-water tank | Choose the 3rd gen only where the regional system is supported. |
| Dual fuel, unusual wiring or zone controls | Verify carefully and consider professional installation. |
| Want current Google Home, Matter or stronger future-proofing | Compare a current Nest or Matter-compatible competitor. |
A practical price rule is simple: the 3rd gen usually wins when its premium is small. The Nest E only becomes compelling when the discount is meaningful enough to compensate for its narrower compatibility and older product status. Do not pay nearly-current-thermostat money for either one.
Should you buy a newer thermostat instead?
For a new installation, compare the older models with Google’s current options before committing. The 4th-generation Nest Learning Thermostat is the current premium successor, with current Google Home setup, Matter support and a newer temperature sensor included in the current bundle. Google’s US Store showed a $279.99 price signal in August 2026, but prices and promotions change.
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The current Nest Thermostat is the lower-cost Google option; Google showed a $129.99 list price and a $99.99 promotional price on one page during the same period. It uses Google Home, but it does not support the Nest Temperature Sensor and is less suitable for homes requiring humidifier or dehumidifier control.
Also consider an ecobee Smart Thermostat Premium if room sensors and broader smart-home integration are priorities, or the Amazon Smart Thermostat for an Alexa-centered home. Matter-compatible thermostats may be a better fit if you want flexibility across smart-home platforms. Availability and pricing vary, so verify current details with the manufacturer.
Used and refurbished buying checklist
- Identify the model. Confirm that it is the 3rd-generation Learning Thermostat or Nest E, not the 2020 Nest Thermostat.
- Check compatibility first. Use Google’s checker and verify terminals, stages, heat-pump behavior, accessories and zone controls.
- Ask for a factory reset. The seller should remove the thermostat from the previous account and reset it before shipment.
- Require a return option. Compatibility may not be clear until installation begins.
- Inspect the hardware. Check the screen, ring, base, mounting plate, trim plate, screws and wire connectors.
- Confirm warranty terms. Google’s comparison information showed two years for the 3rd gen and one year for the E, but used, refurbished and third-party products may not receive the original warranty. Verify the region and seller’s coverage.
- Budget for power hardware. If no C wire is available, check whether a Nest Power Connector is compatible.
- Do not assume regional interchangeability. A non-US Nest E may have different electrical, app or system compatibility.
Installation and testing
Before disconnecting anything, photograph the original wiring. Switch off HVAC power at the breaker or service switch, follow the wiring diagram generated in the Nest app and never treat wire color as proof of function.
Stop and call a professional if the app identifies an incompatible system, or if the installation involves dual fuel, a communicating HVAC system, zone controls, a boiler, accessory equipment or uncertain wiring.
After installation, test heating, cooling, fan operation, emergency heat and each available stage. Confirm remote control away from your home Wi-Fi, verify schedule and Eco behavior, and monitor the system through complete heating and cooling cycles. Repeated reboots, low-power warnings, offline behavior or short-cycling indicate that the installation needs attention.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
