I'm not really looking for solutions here, just looking for explanations after a less-than-stellar experience.
My previous apartment came with a Nest Learning Thermostat. For the 18 months that I lived there, it worked fine with minimal issues. However, part of the move-out checklist involved disconnecting the device from my Google Home app and performing a factory reset. This is one of the last things I did before I left the apartment, along with packing up my internet modem/router. Although the Nest was not connected to the internet, it appeared to be connected to the HVAC and working fine, and I left it on the Heat/Cool setting to keep the apartment roughly between 65 & 75 degrees.
Fast-forward a month: I received my last utility bill for that property, and, during the three weeks between my move-out and the next tenant's move-in, the unit consumed exponentially more power. The kWh usage and bill were 8 times that of the next-highest billing period. To my knowledge (and according to the landlord), the unit was completely vacant and locked during that period, and the only explanation I or the utility company can think of is excessive HVAC activity. The utility company asserts that its usage readings are correct, since usage returned to normal levels around the time that a new tenant transferred the service to their name. So basically I'm wondering what could have happened.
Does factory resetting the Nest affect its ability to sense temperature properly? Does the Nest enter some emergency heat/cool setting when disconnected from the internet? Could a lack of internet connection affect the Nest's connection with the HVAC?
