Editor’s note: This comparison replaces our earlier ecobee3 vs ecobee4 article, which is no longer available. It was rewritten in November 2026 from ecobee’s own product pages (archived copies linked at the end). Both models have been discontinued. By late 2019 ecobee listed the ecobee4 as sold out and was selling the SmartThermostat with voice control in its place, so this guide is most useful if you already own one of these thermostats or are considering a used or remaining-stock unit.
Quick answer
- The big difference is voice. The ecobee4 has Amazon Alexa built in, with far-field microphones and a speaker. The ecobee3 has no microphone or speaker, though it can be controlled through a separate voice assistant.
- Most other specs match: the same 3.5-inch, 320 × 480 touchscreen, the same HVAC compatibility (2H/2C conventional, 4H/2C heat pump), the same temperature ranges, a room sensor in the box, Apple HomeKit support and a 3-year warranty, according to ecobee.
- Choose the ecobee4 if you want a thermostat that doubles as an Alexa speaker. Choose the ecobee3 if you don’t need built-in voice and want the smaller unit.
The ecobee3 and ecobee4 are two generations of ecobee’s Wi-Fi smart thermostat. Both read the temperature in other rooms using wireless room sensors, which is still ecobee’s signature feature. The ecobee4 kept almost everything from the ecobee3 and added Amazon Alexa. Here’s exactly what changed, based on ecobee’s published specifications.
ecobee3 vs ecobee4 at a glance
| Specification | ecobee3 | ecobee4 |
|---|---|---|
| Built-in voice assistant | No | Amazon Alexa Voice Service |
| Microphones and speaker | No | Yes, far-field voice recognition |
| Display | 3.5″ full-color LCD touchscreen, 320 × 480 | 3.5″ full-color LCD touchscreen, 320 × 480 |
| Thermostat size | 100 × 100 × 22 mm (3.93 × 3.93 × 0.86 in) | 109 × 109 × 26.1 mm |
| Room sensor in the box | Yes, 1 with detachable stand | Yes, 1 with detachable stand |
| Sensors listed on the thermostat | Not listed on ecobee’s spec page | Temperature, humidity, occupancy, proximity |
| HVAC compatibility | Gas, oil, electric, dual fuel; conventional 2H/2C; heat pump 4H/2C; humidifier, dehumidifier, ventilator, HRV/ERV | Same |
| Power | 24 VAC via C wire, or Power Extender Kit | 24 VAC via C wire, or Power Extender Kit |
| Wi-Fi | 802.11 b/g/n, 2.4 GHz | 802.11 b/g/n, 2.4 GHz |
| Data use | 15–20 MB/month | 15+ MB/month, depending on Alexa use |
| Works with | Apple HomeKit, Samsung SmartThings, IFTTT, Wink and others | Apple HomeKit, Amazon Alexa, Samsung SmartThings, IFTTT and others |
| Temperature sensitivity | ±0.9 °F (±0.5 °C) | ±0.9 °F (±0.5 °C) |
| Humidity sensitivity | ±5% RH | ±5% RH |
| Set-point range | 44–92 °F (7–33 °C) | 44–92 °F (7–33 °C) |
| Warranty | 3 years | 3 years |
All figures are from ecobee’s product pages at the time each model was sold. ecobee lists the Power Extender Kit as “optional for installation” in both boxes.
What both thermostats share
Room sensors
Ordinary thermostats only measure the temperature where they hang, often a hallway. Both models come with a wireless room sensor that you place in a room you care about. It reports temperature and detects occupancy, so the thermostat can keep the rooms you actually use comfortable. Additional sensors were sold separately in two-packs.
Follow Me and Smart Home/Away
Follow Me averages the temperature of sensors that detect motion, or all selected sensors regardless of motion. Smart Home/Away overrides your schedule if it senses you’re home during an Away period, or away during a Home period.
Energy and equipment features
ecobee lists the same feature set for both, including:
- Smart Recovery: uses local weather and your home’s heating and cooling history to reach the target temperature on time.
- Home IQ: monthly energy reports.
- Alerts and reminders: equipment alerts and service reminders.
- AC overcool to dehumidify, fan dissipation and free cooling (with a ventilator).
- Multistage support for two-stage heating and cooling equipment.
Power and installation
Both are hardwired and powered by 24 VAC through the C wire. If your home doesn’t have a C wire, ecobee’s Power Extender Kit lets you power the thermostat without running a new wire. It installs at the HVAC equipment, so consider a professional if you’re not comfortable working on your furnace or air handler. ecobee’s online compatibility checker was the recommended first step for both models.
ecobee3
The ecobee3 introduced the room sensor approach that ecobee is known for. It’s a little smaller than the ecobee4 at 100 mm square, and ecobee listed it as Apple HomeKit enabled, so you can control it with Siri from an iPhone or iPad. It has no built-in microphone or speaker. For voice control you’d pair it with a separate assistant.
Pros
- Room sensor included
- Apple HomeKit enabled
- Smaller unit on the wall
- Same core HVAC compatibility as the ecobee4
Cons
- No built-in voice assistant
- Discontinued, so new units are hard to find
Read our full ecobee3 review for more detail.
ecobee4
The ecobee4 adds Amazon Alexa Voice Service, with built-in microphones using far-field voice recognition and a built-in speaker. You can adjust the temperature by voice and use other Alexa skills such as timers, shopping lists and music, without a separate Echo. A light on top of the thermostat shows when Alexa is listening, and you can adjust the volume in the ecobee app. ecobee also lists proximity sensing on the thermostat itself.
Pros
- Alexa built in, with microphones and a speaker
- Room sensor included
- Works with HomeKit, Alexa, SmartThings and IFTTT
- Lists temperature, humidity, occupancy and proximity sensing
Cons
- Slightly larger unit than the ecobee3
- Alexa adds ongoing data use
- Discontinued and replaced by newer ecobee models
Read our full ecobee4 review for more detail.
Which should you choose?
Choose the ecobee4 if…
- You want Alexa on your wall without buying a separate smart speaker.
- You already use Alexa routines around the home.
Choose the ecobee3 if…
- You don’t want a microphone in your thermostat.
- You already have a smart speaker or use Siri through HomeKit.
- You prefer the slightly smaller unit.
If you’re buying new today, both models have been replaced. Compare ecobee’s current thermostats, or see our ecobee vs Nest comparison and our thermostat buying guide for what to look for.
Bottom line
The ecobee3 and ecobee4 are nearly identical thermostats: same screen, same room-sensor system, same compatibility and same 3-year warranty. The ecobee4’s built-in Alexa is the reason to pick it. If you don’t need voice control on the thermostat itself, the ecobee3 does the same heating and cooling job.
FAQ
What is the difference between the ecobee3 and ecobee4?
The ecobee4 has Amazon Alexa built in, with microphones and a speaker. Otherwise ecobee lists the same display, room sensor, HVAC compatibility, temperature ranges and warranty for both.
Does the ecobee3 work with Alexa?
It has no built-in Alexa, but ecobee marketed it for voice control through a separate assistant. ecobee also listed it as Apple HomeKit enabled.
Do the ecobee3 and ecobee4 need a C wire?
Both are powered by 24 VAC through the C wire. If you don’t have one, ecobee’s Power Extender Kit lets you install the thermostat without running a new wire.
Do they come with a room sensor?
Yes. ecobee lists one room sensor with a detachable stand in the box for both models.
Are the ecobee3 and ecobee4 still sold?
No. Both have been discontinued, and ecobee replaced them with newer thermostats such as the SmartThermostat with voice control.
Sources: ecobee4 product page and technical specs (archived December 2019); ecobee3 product page and technical specs (archived 2017).
