@Apartment-By-The-Sea0 Any additional charges that only go into effect on or after the end of the stay require that you request money via Resolution Request. The guest can then refuse the charge, at which point the case goes to an Airbnb mediator who may decide in their favor. Of course during this process the guest will review and rate your listing, perhaps less favorably than they would have otherwise. High risk + low reward does not strike me as a very good formula.
If you're unable to install the technology to remotely control AC usage, it seems like the best thing to do is adjust your base prices to make sure you're covered in the event of excessive usage. It may also help to clearly communicate your expectations of energy consumption to each guest, knowing that Airbnb will not back you up for expenses that aren't related to physical damage.