May I pass on energy costs to Airbnb guests?

This depends on the rules in your country and your platform, so check this with an accountant, lawyer, or regulatory authority. With short-term rental, energy is usually considered part of your service, which you factor into your nightly rate instead of charging separately as you would with long-term rental. Billing separately based on actual consumption is permitted in many countries, but you must disclose this clearly in advance and provide your guest with insight into their consumption.