most laptops run on 20-40 watts of power with a screen and most desktop computers have been replaced with laptops and an external monitor. what a power savings of 400 watts all the way down to 1 watt with raspberry pi computers. Microsoft Claims there is 400 active windows 10 installs, probably the same for linux. so some quick math here is 800 million x 40 * 10x the efficiency = 32 trillion watts saved.
