Electricity bills are no joke!
But this app is.

Turn off the light to keep your bill down. But watch out! You never know when you'll find the light back on, running your bill up! As you unlock new rooms try to keep your room in the positive or you will get locked out at the end of the week. Remember, with great power comes great responsibility.

If things start to get out of hand, you can turn the room off by tapping on the lock above the room. Tap it again to turn the room back on.

If you want to apply this idea to your own home, we're sure your bill-payer won't mind.