It has to be connected to WiFi to download an update (but once downloaded, it can be installed at any time), but it doesn’t need to be plugged in.Does the car have to be charging and connected to wifi to update?
You will be notified that a new software update is available even if the car is not connected to WiFi (i.e., that is done over the 4G network) but the update won’t be downloaded unless the car is connected to WiFi directly or via your phone in hotspot mode.