Smart Thermostats require a certain amount of wires to work appropriately. The number of wires depends on your HVAC equipment, but most heating and cooling systems require at least 5 wires. There are some options to solve this; such as power extenders, running more wires, using remote sensors or using the existing wires with some sacrifices in functionality. Ross explains the later, by sacrificing fan control (individual fan mode on/off control) and reusing the Fan “G-wire” as the Common “C-wire” this will allow the thermostat to be powered 24/7/365 without any issue of low battery. Simple fix without major compromises.