No problem if you don't want to use an app, just use the thermostat. The system runs fine without internet connectivity. What you get with a wifi connection is

No problem if you don't want to use an app, just use the thermostat. The system runs fine without internet connectivity. What you get with a wifi connection is the thermostat can access signals that increase system efficiency (demand response, weather, TOU rates) and you get remote commands from your smartphone.