What is a c-wire?

A c-wire (also referred to as a common wire) is a low voltage power wire that many Wi-Fi thermostats require for their features to work. A lot of homes don’t have a c-wire because older thermostats didn’t require one. The Sensi Wi-Fi Programmable Thermostat is one of the few Wi-Fi thermostats that does not require a c-wire in most cases, making installation quick and easy. However, if you have a c-wire, it is recommended that you connect it.