I’m too “green” to leave the lights and T.V. on but I used to put on the radio. Also, some hotels you need to use your key card to turn on the electricity. I noticed though that some still let you run the T.V. without it. Also, you can override the system by putting, not a credit card, but dig around for some store card that’s not worth anything to anyone else. Any card the right shape will work.

In older hotels with keys with numbers, I turn those into the desk. No need to lose that while out and about. I keep key cards, +without+ the room number, with me but not old fashioned keys. Be sure to throw away the cardboard and just carry the key card.

Not sure if this is industry-wide but we had more problems with hotels, even deaths, with my two airlines than with any on board incidents.