@Paolo9
you can send a request for reimbursment but the traveller is not obliged to pay.
@Oad0 is right is saying it is easier to incude it in the price because the host is sure to be paid.
Another solution is to NOT check AC box in the equipments and write the price in the house rules.
So you can send a special offer for people who want it.
Or they pay more in advance with a special offer and you can send a reimbursement.
Or they pay less because they consume stupidly and you warn them they consumed it all and the AC will be cut.
When they check in, you can show them how to follow their consumption of electricty during their stay and warn them of the red line so accounts are clear.
But clearly , Airbnb is all costs included.
You may have bad reviews for hidden costs.
Be cristal clear in your listing and emails and don't check the AC box in the equipment if it is not included.