A C wire adapter for a thermostat is a device that allows you to add a C wire at the equipment during Wi-Fi thermostat installations when a common wire is required but not present. The C wire, or common wire, provides continuous power from heating and cooling systems to Wi-Fi thermostats. Most smart thermostats today that are Wi-Fi enabled or have a color touch screen may require constant power through a C wire. If your home operates on a low-voltage heating system, you should be able to locate the C wire behind your current thermostat. If you dont have a C wire connection and have no desire to add one, some smart thermostats can operate with batteries. However, if you need a C wire for your smart thermostat, you can use an adapter like the Honeywell Home C-Wire Power Adapter. The adapter is easy to install and provides a consistent power source, ensuring your smart thermostat functions smoothly without any power-related issues.