Does their granny flat have its own power supply? If they are using excess power and having lights on late at night because they have friends over (that they haven't checked with you if it is ok to have over), turn the power off.

They may choose to sit and drink in the dark. That is their choice, but you shouldn't have to be paying for their excessive use especially if they getting more cash than you. In the real world, if you don't pay it gets cuts off.

Same with the dryer, if its not necessary don't allow them to use it. They will start to think about washing stuff so it has time to dry.

This is tough love stuff, but it won't hurt them. And will prepare them more for when they are out on their own.

Just as an aside, is your daughter covered contraceptively? It sounds like they aren't looking after themselves, you don't want to add another kid into the mix.

Take care,

K