The modeling is already happening: the parent is sweeping through the house every morning doing what the kids should be doing for themselves. The message is wrong: THEY are to be responsible, not the parent. A habit takes about 3 weeks to be ingrained & positive reinforcement helps.
I suggest a short, to the point meeting with both kids telling them what you expect & why they should do it (save resources, money, self sufficiency, & it’s the right thing to do). Teach them that they only turn the water on to rinse their toothbrush & mouth, then turn it off — don’t let the water run while brushing. Lights off when leaving a room, including the closet.
Come up with a treat you know they’ll like (movie, ice cream out, etc) & tell them they have to turn everything off for a week to earn it. No reminding from you. Any lapse & the week resets. Suggest your kids police each other if necessary. Have a physical something to mark progress; mark a calendar or chart. Yes, you’ll have to still sweep through the house to check. If they fail, don’t relent, just tell them it’s a bummer they forgot & you know they’ll do better, but insist on the week. Then, after the successful week, you may want to up the prize & require 3 straight weeks.
If there’s constant backsliding, you have a different problem & need a consequence that you are so “tired” of doing for them (or a particular kid) that privileges will be curtailed until you see improvement.