Thermostat Satellite Sensors Changed How I Heat My Home

Even the smartest thermostat has one universal flaw: It's stuck in place. Smart thermostat brands set out to solve that problem, and the result was a small add-on device that I am beginning to consider nearly mandatory for proper smart temperature management in my home. Here's how it works.

Why do smart thermostats need an extra sensor?

Whole-house thermostats tend to be in central locations like main hallways and large, open walls. But that means their onboard temperature sensors don't always reflect the comfort level where you are -- like a living room, bedroom or kitchen.

If the thermostat is too near a vent and gets lots of hot air, for example, it's going to register higher and shut off while you're still shivering back on the cold kitchen tile. If it's stuck in a drafty hallway, you may start sweating before it finally shuts off.

Satellite thermostat sensors are portable, battery-powered models that address this problem.

How do satellite sensors work with thermostats?

Satellite sensors are small temperature sensors designed to be activated and placed wherever you want, preferably in a room where you spend a lot of time, or a place that always seems too hot or cold.

The sensor sends back the temperature at its location, and the smart thermostat uses that information to make better decisions about when to turn heating and cooling on or off. That helps your comfort expectations match reality more accurately.

In my house, I typically keep the Nest Thermostat sensor in my study, which stays notably colder than the rest of the house and could use a heating boost, especially in the morning. In the Google Home app, I can select whether the Nest Thermostat will use the sensor to judge its temperature requirement or to use its own built-in sensor depending on where people in the house are spending the most time -- or to average the two together, which seems to be the best option in my home.

These sensors aren't just for comfort, either. When used correctly it may be able to help you save money by avoiding overheating or overcooling a room no one is using. They could even help prevent frozen pipes in a cold room.

Who offers satellite sensors for their thermostats?

Major thermostat brands including Google Nest thermostats, Ecobee thermostats and Honeywell thermostats offer portable sensors for compatible units. They're getting more common, too: Now that we're on the second and third generations of satellite sensors, companies are packaging them together more frequently and offering them at lower prices.

Notably, Amazon has a unique take with its Amazon Smart Thermostat ($80). Instead of a dedicated satellite sensor, it can use devices such as an Echo Dot 5 or Echo 4 as temperature sensors for the same purpose.

How much do satellite sensors cost?

You can find cheap portable temperature sensors everywhere, but the key is finding one that connects with your smart thermostat. In most cases, it's best to buy directly from the same brand as the thermostat.

The newest thermostats we've reviewed, like the Nest Thermostat 4 and the Ecobee Smart Thermostat Premium, include a temperature sensor alongside the smart thermostat so you don't even have to buy an add-on. If you need to buy them separately, you can find the Nest sensor for $40, an Ecobee satellite sensor two-pack for $100 and a Honeywell sensor two-pack for $80, among others.

Can I use multiple temperature sensors?

In many cases yes, and that comes with additional advantages. If you use multiple Ecobee sensors, you can set them to sense when people move from one room to the other and set heating requirements for the room where everyone is currently chilling (or uh, heating). Multiple Nest thermostat sensors allow you to average the temps of all sensors in the home so the thermostat gets a broad view of all major rooms when reaching its set level.

Are there any downsides to using a portable thermostat sensor like this?

Those that have batteries will need to have them replaced every year or two, although their apps should send you alerts about it. In our tests, we sometimes found that it was hard to tell if satellite sensors were working (indicator lights would be a nice upgrade for many) or when they had become disconnected, so some troubleshooting may be needed.

To learn even more, check out our list of the best space heaters, if a heat pump is better than a furnace, and how you can use a heat pump even in an apartment with this window model.