If you’re upgrading your HVAC thermostat, it’s a good thing to find out in advance if your existing system provides a c-wire.
Today’s smart thermostats provide a great deal more options and convenience such as wifi connectivity and a bigger, brighter, multi-functional control screen. These improvements typically draw more electricity than the existing thermostat you’re replacing. The c-wire (“c” stands for “common”) is an important extra electrical wire that enables continuous 24-volt power to operate newer smart thermostats. If you don’t have one installed with your existing model, you’ll probably need to have it installed in order to adequately power the new unit.