Smart thermostats are becoming more and more popular. Learning thermostats like the Nest help keep your home comfortable and can save you money on your energy bills. Smart thermostats with remote sensors, like the Ecobee4, can control the temperature in your house on a room-by-room basis. Purchasing one of the top smart thermostats is a no-brainer. The hard part is determining whether or not a new thermostat is compatible with your heating and cooling system. Before making a new purchase it’s important to understand how to wire a thermostat. When it comes to wi-fi or programmable thermostats, compatibility often comes down to the C-wire (or Common Wire).