Electricity

[Kay Rock]

I have a studio attached to my home that I rent to a young couple. They have been living there 4 months and the electricity bill has gone up 200%. I know it's summer, so we use more, but since they have moved in they haven't turned off the window unit AC. I've if they could turn it off when they're not at home, and was told that they won't turn it off because the studio will take too long to cool down when they get home. What can I do?