If you travel in Europe or Asia, many of the hotels use one of these slots next to the door to control power for the room. Put your room key in when you arrive and the power turns on. Remove the key and after a few seconds the power shuts off. Based on something I read recently, it saves the hotels about $10-12 per room per year because all the stuff you forget to turn off powers down. The downside is if you’re trying to charge your laptop the power is gone when you leave and the air conditioning stops cooling the room.

At both hotels I stayed at in China, the hack for this is to stick a business card in the slot instead of the key. I’m sure hotels will eventually catch on, but in the meantime, you can leave the room and still charge your batteries. Kudos to Lee and Sachi for giving me the idea in the first place.