An ecobee sensor is a small wireless remote that measures temperature and detects whether someone is in the room. Your ecobee thermostat uses it to heat or cool for the rooms you actually use, instead of the hallway where the thermostat is often installed. Most homes need two, placed about five feet up on an interior wall in the bedroom and the main living space.
This guide explains what the ecobee SmartSensor does, how many you need for your thermostat, where to put each one, and how to set them up so they actually change how your home feels.
Ecobee SmartSensor at a Glance
| Feature | ecobee SmartSensor |
|---|---|
| What it measures | Temperature and occupancy (motion) |
| Range | Up to 60 ft from the thermostat |
| Battery | CR2477 coin cell, up to 5 years |
| Maximum per account | 32 sensors |
| Works with | Every current ecobee thermostat, plus ecobee4, ecobee3 and ecobee3 lite |
| Sold as | A 2-pack, $99.99 list price |
| What it unlocks | Room averaging, Follow Me, Smart Home & Away |
If you have the older ecobee room sensor (the one sold with the ecobee3), keep in mind that it doesn’t work with the Smart Thermostat Essential or Smart Thermostat Lite. The current SmartSensor works with all of them.
What an Ecobee Sensor Actually Does
An ecobee smart sensor gives your thermostat more than one place to read the temperature from. That matters because the thermostat’s own sensor only knows the temperature in the spot where it’s installed. If it’s in a hallway, it can read 70°F while the bedroom upstairs is at 66°F.
Your thermostat uses the sensors in three ways:
- Averaging. For each Comfort Setting (Home, Away, Sleep and any you create), you choose which sensors count. The thermostat averages the ones you chose. For example, the bedroom sensor can count only during Sleep, so the bedroom stays at the temperature you set all night. You can even remove the thermostat’s own sensor from a Comfort Setting, as long as at least one remote sensor is still included.
- Follow Me. When it’s on, the thermostat gives more weight to the rooms where it has detected people recently, among the sensors included in the current Comfort Setting. On the Essential, the Lite and the ecobee3 lite, Follow Me needs two sensors.
- Smart Home & Away. If no one is detected for two hours during a scheduled Home period, the thermostat switches to an energy-saving temperature. It switches back when it detects you again. The Premium and Enhanced have built-in radar occupancy sensing, so they can do this alone, but the Essential, Lite and ecobee3 lite need at least one SmartSensor.
The sensor also has limits. It doesn’t measure humidity, only temperature and occupancy. And it can’t send more air to one room: on a system with one zone, every room gets heated or cooled at the same time. When the thermostat prioritizes the bedroom at night, the other rooms simply drift warmer or cooler. If one room is always much hotter or colder than the rest, the sensor will tell you by how much, but the real solution is the airflow (vents, ducts or zoning), not more sensors. For that, smart vents can move more air to one room, and Flair’s vents can use your SmartSensors as their room sensors.
How Many Ecobee Sensors Do You Need?
ecobee doesn’t give a number: its own advice is that it depends on your home and your preferences, up to 32 sensors per account. In practice, the right number depends mostly on which thermostat you have and how many rooms you care about.
| Your setup | Built-in occupancy sensor | Sensors to start with |
|---|---|---|
| Smart Thermostat Premium | Yes (radar), plus one SmartSensor in the box | The included one; add a 2-pack for a second floor or a problem room |
| Smart Thermostat Enhanced | Yes (radar) | 1 or 2: the main bedroom and the room that’s too hot or too cold |
| Smart Thermostat Essential or Lite | No | 2, the minimum for Follow Me |
| Two-story home | Depends on the model | At least one on the floor without the thermostat |
| Bedrooms on different sides of the house | Depends on the model | One in each bedroom you want to keep comfortable at night |
A good rule is one ecobee room sensor in each room where comfort really matters, plus one on every floor away from the thermostat. For most homes that’s two, which is why the 2-pack is the usual starting point. If you’re comparing brands, our guide to thermostats with remote sensors covers the Nest, Honeywell and Aqara options too. If you have a Nest, our Nest Temperature Sensor guide covers Google’s sensor. Beyond four or five sensors on one system, each extra sensor changes the average less, so add more only for a room with a specific problem.
If you’re still choosing a thermostat, our comparison of the ecobee Essential, Enhanced and Premium explains which models include a sensor and which have built-in occupancy sensing.
Where to Place Ecobee Sensors
Good ecobee sensor placement matters as much as the number of sensors. ecobee’s own placement advice is:
- On a wall: use an interior wall, about five feet from the floor, facing the room.
- On a shelf or table: about four feet high, on the detachable stand.
- Away from direct sunlight, which affects both the temperature and the occupancy readings.
- Away from exterior walls and windows, so the outside temperature doesn’t affect the reading.
- Away from vents, fans and drafts.
- Away from devices that give off heat, such as TVs, lamps and the thermostat itself.
The occupancy sensor sees about 20 feet in front of it, so put it where it faces the part of the room you use, like the bed or the sofa, not behind a door.
As for which rooms, start with the ones where you spend the most time: the main bedroom for Sleep, and the living room or home office for Home. Next, add a sensor to any room that’s always warmer or colder than the rest, such as a room over the garage or a basement. Avoid a busy hallway or a spot near the stove, where people walking by and cooking heat would affect the readings.
ecobee rates the sensors for up to 60 feet from the thermostat. However, walls, floors and other devices on the same 915 MHz frequency (such as some baby monitors and cordless phones) shorten that range, and ecobee lists distances over 45 feet as one cause of sensors dropping their connection.
How to Set Up an Ecobee SmartSensor
You pair a SmartSensor in the ecobee app. Keep the sensor near the thermostat, but at least 24 inches away from it, and don’t mount it on the wall until it’s paired.
- In the ecobee app, tap the + sign on the Home screen, then Add a device > Room Sensor > SmartSensor.
- Tap Let’s get started and scan the QR code on the sensor’s plastic pull tab. You can also type the pairing code manually.
- Pull the tab to power on the sensor and pair it.
- Choose a name for the sensor, usually the room it’s going in.
- Choose your thermostat and the Comfort Settings the sensor should be part of (for a bedroom, Sleep is often enough).
- Mount the sensor on its stand or with the adhesive wall bracket, then tap Done.
Then turn on the features that use it. On the thermostat, go to Main Menu > General > Sensors > Follow Me, and to Main Menu > General > eco+ > Smart Home & Away. In the app, both are under the thermostat’s Menu. To change which sensors count later, go to Comfort Settings, choose one, then Sensor Participation. On the Essential and Lite, Sensors and Comfort Settings are directly under Main Menu, without General. ecobee’s SmartSensor setup and placement guide has the same steps with screenshots.
One thing that confuses people is a hold. During a manual hold, the thermostat uses the sensors included in the Home Comfort Setting, whatever the schedule says. If you’re not sure what a hold does, see what hold means on a thermostat.
If your ecobee is connected to Apple Home (our guide to how ecobee works with HomeKit explains the setup), the sensors show up there too, as a temperature sensor and an occupancy sensor for each room. You can use them in HomeKit automations, for example to turn on a light when someone enters the room, although the readings don’t update instantly. Our guide to HomeKit temperature sensors compares them with dedicated HomeKit sensors.
If a Sensor Shows N/A or Won’t Pair
When a sensor shows “N/A” on the thermostat, it has lost its connection. ecobee lists three usual causes: a low battery, a sensor more than 45 feet from the thermostat, or interference from walls or other devices.
To fix it:
- Cancel any active hold on the thermostat.
- Unpair the sensor (Main Menu > General > Sensors, select it, then the trash icon).
- Take the battery out of the sensor.
- Take the thermostat off the wall for about two minutes, then put it back.
- Start pairing again in the app, scan the QR code, then put the battery back in.
If it still drops out, put in a new battery. The SmartSensor needs a CR2477, and CR2477N batteries don’t work in it. To check whether distance is the problem, leave the sensor next to the thermostat for 24 hours: if it stays connected there, move it closer to the thermostat or away from the device causing interference. For problems with the thermostat itself, see our guide to an ecobee thermostat that’s not working.
SmartSensors Worth Buying
The room SmartSensor is the one most homes need. The door and window version and the Premium bundle are for more specific situations.
ecobee SmartSensor 2-Pack — Best for Most Homes
The two sensors most ecobee owners need, and the minimum for Follow Me on the Essential and Lite.
Best for: Any ecobee owner who wants the bedroom and the main living space at the right temperature.
What stands out in real use
Two sensors cover the most common setup: one in the main bedroom for Sleep and one in the living room or a problem room for Home. Each one reads temperature and detects occupancy, so they improve the averaging and also let Follow Me and Smart Home & Away work on an Essential or Lite. Each one runs for years on its coin cell battery.
Key specs
- Temperature and occupancy sensing (about 20 ft detection range)
- Up to 60 ft from the thermostat, 915 MHz
- CR2477 battery, up to 5 years
- Detachable stand and adhesive wall bracket
- Up to 32 per account
Pros
- Works with every current ecobee thermostat
- Very long battery life
- Small enough to sit on a bookshelf or dresser
- Shows up in Apple Home through the thermostat
Cons
- Sold only as a 2-pack
- Doesn’t measure humidity
- Only works with ecobee thermostats
Installation and compatibility notes
You don’t need tools: pair it in the ecobee app, then place it on its stand or stick the bracket to an interior wall. It works with the Premium, Enhanced, Essential and Lite, the SmartThermostat with voice control, ecobee4, ecobee3 and ecobee3 lite.
Price: ~$100 (for a 2-pack)
ecobee SmartSensor for Doors & Windows (2-Pack) — Best for Pausing the HVAC When a Window Is Open
A contact and motion sensor that can stop your heating or cooling when a door or window is left open.
Best for: Homes where windows or a patio door are often left open with the system running.
What stands out in real use
This is a different sensor from the room SmartSensor: it mounts on a door or window frame and tells the thermostat when it’s open, and it also detects motion. With an ecobee Smart Security plan, the thermostat turns off heating or cooling after a door or window has been open for five minutes, then turns it back on about 30 seconds after it’s closed.
Key specs
- Contact and motion sensing
- Up to 60 ft from the thermostat or camera
- CR2477 battery, up to 3 years
- 2 sensors per pack
Pros
- Saves energy when a window is left open
- Also works with ecobee’s Smart Security system
- Small and easy to mount
Cons
- Pause When Open needs a Smart Security Plus or Advanced plan ($5 or $10 per month)
- Doesn’t measure temperature, so it doesn’t help with room averaging
Installation and compatibility notes
It needs an ecobee thermostat or camera to work. ecobee lists the Premium, Enhanced and Essential, plus the ecobee4, ecobee3 and ecobee3 lite.
Price: ~$60 (for a 2-pack)
ecobee Comfort and Security Bundle — Best If You Don’t Have an ecobee Yet
The Smart Thermostat Premium with its room SmartSensor, plus two door and window sensors.
Best for: Anyone buying an ecobee who wants sensors from the start.
What stands out in real use
The Premium is the only current ecobee with a SmartSensor in the box, and it also has built-in radar occupancy sensing, an air quality monitor and built-in voice control (Alexa, or Siri with a HomePod). This bundle adds two SmartSensors for doors and windows. At ecobee’s list prices, it costs less than buying the thermostat and the door sensors separately.
Key specs
- Smart Thermostat Premium with 1 SmartSensor
- 2 SmartSensors for doors and windows
- Power Extender Kit for homes without a C wire
- Works with Apple Home, Alexa, Google Home and SmartThings (no Matter)
Pros
- Room sensor and occupancy sensing out of the box
- Premium’s air quality monitor and built-in voice assistant
- Door sensors ready for Pause When Open
Cons
- Costs more than buying a thermostat and a 2-pack if you don’t need the door sensors
- Pause When Open still needs a Smart Security plan after the free month
Installation and compatibility notes
The Premium installs like any ecobee: it works with most 24 V heating and cooling systems, and the included Power Extender Kit helps when you don’t have a C wire. If you’re not sure about your wiring, read our guide to installing a smart thermostat first.
Price: ~$245
Conclusion
The SmartSensor lets your thermostat heat and cool for the rooms you use instead of the hallway. Most homes need two: one in the main bedroom, included only in Sleep, and one in the living space or the room with the comfort problem. Place them about five feet up on an interior wall, away from sunlight, vents and electronics, and pair them in the ecobee app before mounting them. If you have an Essential or Lite, two sensors also unlock Follow Me, and one unlocks Smart Home & Away.
How many ecobee sensors do I need?
Most homes need two: one in the main bedroom and one in the living space or a room that’s often too hot or too cold. Add one on each floor away from the thermostat. On the Essential and Lite, two sensors are also the minimum for Follow Me.
Where should I put an ecobee sensor?
ecobee recommends an interior wall about five feet from the floor, or a shelf about four feet high, facing the room. Keep it away from direct sunlight, exterior walls and windows, vents, fans and devices that give off heat, including the thermostat.
Do ecobee SmartSensors work with the ecobee Essential?
Yes. The SmartSensor works with every current ecobee, including the Essential and Lite. The older ecobee Room Sensors don’t work with those two models.
Does the ecobee SmartSensor measure humidity?
No. The SmartSensor measures only temperature and occupancy. If you want humidity readings in individual rooms, you need a separate humidity sensor.
How long does the ecobee sensor battery last?
ecobee rates the SmartSensor’s CR2477 coin cell battery for up to five years. Replace it with a standard CR2477, because CR2477N batteries don’t work in it.
Why does my ecobee sensor say N/A?
N/A means the sensor has lost its connection to the thermostat, usually because of a low battery, too much distance or interference. Replace the battery or unpair it, restart the thermostat and pair it again in the ecobee app.
Written by Evan Mercer
Founder & Lead Researcher, Smart Home Matrix
Evan digs through spec sheets, firmware changelogs, and thousands of owner reviews so you don’t have to. Every guide starts with a compatibility check and ends with picks he would install in his own home. Read more about Evan and this site, or see exactly how we choose products.