Hello 
Has anybody tested if there is a difference of power consumption when I disconnect the Photon from the cloud but leave the WiFi still on?
Best regards
I have not tested it. However, the cloud connection only sends a cloud ping every 10 seconds, and it’s only a couple hundred bytes. The amount of energy that requires will be dwarfed by the 45 mA that the STM32 and Wi-Fi module use, even when idle.
So it will have an effect, but probably not one that will meaningfully affect your power consumption.