The tado° app always uses the most battery-efficient way to determine how far you are from home (e.g. with iOS geofencing/region monitoring) and works in the background. GPS is only called upon in exceptional cases. This takes place fully automatically. If you have deactivated the GPS function, tado° uses the other geolocation functions of your smartphone. In general tado° always uses the last distance from home that has been transmitted by your phone. This information is used to determine the level of heating. In case your phone does not send location data (e.g. when deactivating all geolocation functions), tado° will use the distance of the phone that was last transmitted.