Air Conditioner

[Azul0]

Hello, I rent a whole house in the beach. (Cancun) I just received a couple with three dogs who asked me for a discount if they stayed a month.  I am not charging anything extra fr the pups, eventhough I am going to have to pay extra for the cleaning because they are pretty gross (humans, not dogs).  The problem is they have the air conditioner ON DAY AND NIGHT.  I ask them to turn if off if they are out, but since the dogs stay in, they leave the AC on.  The bill was gone over the roof.  How can I ask for them to pay the difference it has amounted to- from their maniac use of AC to the normal - the one I have every other month?