With the heat that the sun is emitting, adding switched on lights will make the surrounding even hotter. There are adults who do not care whether it is left on despite it being of no use for that moment like if you leave the room and no one else is there. If you went to the kitchen and found something to eat and you did eat, the bedroom light that was left on will be heating the room and adding consumption to your bill. It’s never too late for kids, though. Give your switchplates interesting design and it will catch the attention of the kids as they go out the room, hoping they also get into the habit of switching it off.