The Good: Small, lightweight and portable. The Nest Temperature Sensor can be placed virtually anywhere or mounted with the included drywall screws. Extend Nest’s ability to measure temperature to any part of your home. Able to schedule which sensor controls the temperature at which time.
The Bad: These are expensive at $40 for one or $99 for three. Only work with Nest Generation 3, Nest E or later thermostats. Nest doesn’t learn to use a particular sensor at a particular time or take an average of the temperature across sensors.
Overall: These are convenient if you spend the time to set them up, but at the price I would expect them to be a little smarter. Manually selecting which sensor to use, or scheduling the Nest to take temperature readings from one sensor at a time is a half-assed solution, when the thermostat could easily use all sensors to get a better temperature reading for a zone. If you can score these on sale, they may be worth it for you, but don’t expect a big upgrade to your thermostat that doesn’t take intensive setup on your part.
Unless your house is hermetically sealed, it’s likely that you have areas of the house where the temperature always seems to be different than the rest of the house. For the longest time, this was the big selling point for Ecobee thermostats, as they came with a separate temperature sensor and the ability to add more. In 2018 Nest announce their temperature sensors as an answer to Ecobee.
These Nest temperature sensors are a little under two inches (1.9 inches) in diameter and .8 inches high, and weigh 1.6 ozs, so they can be hidden virtually anywhere. The included battery should last up to two years before it needs to be replaced. They can be placed up to 50 feet away from the controlling thermostat depending on your home and obstructions. One of the big drawbacks is that they’re only compatible with the Nest 3rd Generation or Nest E thermostats (and anything to be released in the future). If you have a 1st or 2nd generation Nest thermostat, you wont be able to use these. According to Nest, you can pair six sensors to a single thermostat and up to 18 in a single home. If you need 18 temperature sensors, I’d love to see your home!
Setting up these sensors is extremely simple. After tapping “Add device” in the app, you’re prompted to scan the QR code on your sensor, then pull out the battery tab to activate it, place it, and test the communication. You’d like these to be set it and forget it, but that’s where these really fail.
Instead of using Nest’s famed learning feature to decide which sensor needs attention, it asks you to either manually switch between sensors, or assign sensors to automatically take control at one of four designated time slots: Morning, Midday, Evening, and Night. This is cumbersome for users and seems like Nest took a shortcut to get the sensors into the ecosystem. I’d say that I expect them to make these sensors smarter in the future, but don’t hold your breath.
The Nest temperature sensors are fit for purpose, despite their lack of smarts, and they do a great job of measuring the temperature in other areas of your home. I placed three of them on my second floor and quickly found that my daughter’s bedroom is routinely four degrees colder than the rest of the floor. Switching the thermostat to use that sensor instead of the thermostat in the hallway as the primary measurement quickly brought her room up to the correct temperature while only increasing the rest of the floor about one degree.
My home has central air controlled by the upstairs thermostat, which means my first floor often remains warmer than my second floor. In the summer, I’ll move one of the sensors to a room downstairs and attempt to use that to normalize the temperature difference between the first and second floors. Given that Nest doesn’t automatically poll multiple devices, my fear is that the second floor will reach zero degrees Kelvin before my first floor sensor turns off the thermostat.
While Nest did a good job of making these sensors virtually invisible, they could have spent more time making them work seamlessly with the thermostat with a lot less user setup. I expect better things from them and I’m continually disappointed with their mantra of “iterate rather than innovate.” At the price of $40 for one or $99 for three, I couldn’t recommend running out to buy these unless you had a burning need to deal with hot or cold spots in your home. And if you have the cash and the motivation to do that, caulk and insulation are a lot cheaper alternatives.