Came out today due to customer keeps having to pull thermostat off the wall to charge it. Opponent inspection of the system found the nest thermostat did not have a common wire but the thermostat wire had plenty of wires to add a common. Performed full inspection over the entire system. Found gas furnace in the attic with AC coil. Upon inspection of the gas furnace found that the heat exchanger is very rusty, the indoor bar motor has large amount to build up, the capacitor on the outdoor unit for the compressor is bad, the system is low on 410 a refrigerant, there is no TE standard flood protection on the system, there is no UV protection on the system. Presented customer with all options and explain to her the condition of her system, and at this time, she only decided to wire and thermostat to have constant power from the system. Customer stated she did have carbon monoxide detectors. With heating season coming right around the corner recommended to homeowner to replace batteries and