Google Nest thermostats come with advanced temperature sensors and algorithms built in. They’re designed to help keep you comfortable, but thermostats aren’t always installed in the best location. For instance, your thermostat might be tucked away in a closet, or mounted in a drafty hallway.

You might want a temperature sensor if you have a multi-story home and care most about your comfort downstairs during the day and upstairs at night. It might also be useful if you have a baby or elderly family member and want to ensure that the room where they spend their time is comfortable for them.

In cases where your thermostat isn’t installed in a good spot, a separate temperature sensor can help keep you more comfortable by measuring the temperature in a better location and using that temperature to tell your heating and cooling system what to do.