One of the hotels I was in last week reminded me of this:
When Antoine goes down to take out the garbage before bed (at around 18:44), the lights turn off on him while he’d dumping the pail. He clicks it back on. This used to be the norm all over Europe, to cutdown on postwar energy consumption
One of the hotels I stayed in Italy last week had a version of this, where the lights were on a timer and if they turned off before you got to your room, you had to feel around for the switch. Another nicer one had a better system, where the hall lights clicked off then a motion sensor turned them back on if there was anyone in the hallway. This system had been updated with a Fob entry system, which you then (without instructions, must be in wide use) had to insert into a slot inside the room to make the lights work. Guests have to take the Fob with then when they leave the room, thus insuring no lights can ever be left on when the room unoccupied. Italy is so backward.
We already know a ton of ways to save energy. Though of course, instead of these methods, we need an app.