Welcome @Andrea8160 to the community, and also thank you for such a well-worded question, especially as I'm sure many other Hosts have wrestled with knowing what to do in their Countries (and thank you as well, @Shelley159 and @Deepti-And-Nitin0 for both of your excellent replies)
The subject of excesses, whether hot or cold, or anything else that will more than likely have Guests desperate for more heat in colder climes, or Guests equally desperate for ice-cold air-conditioning in hotter regions have been with us all for many years already, but in years to come, it's highly likely that changes to the world's climate may well mean that everyone will be asking exactly the same questions, or saying what they presently do, in order to mitigate the problems, so not only we as Hosts, but Airbnb as the Company, have to take on board that somehow no host is going to be able to survive (and therefore still be a cash-cow for Airbnb's continuing success) unless Airbnb allow all of its Hosts to charge extra, for extra heating and/or cooling.
Years ago in the UK (although I don't know what other Countries allow or not) the majority of holiday properties had coin-operated meters for Guests to use, although if I remember correctly, Guests' had to be prepared to bring the required coins with them so that when the money ran out, or was very low, more coins could be put into the meter.
Personally I believe that what @Shelley159 mentioned about having a certain amount of money already preloaded into such a meter, is an excellent idea, as it should allow Guests to comfortably enjoy their stay, but they also know that once the amount gets low, they'll have to insert more money into the meter. I also agree that the amount put onto the meter before the Guests' arrive should be "sufficient" - maybe be based on how much a "standard" Guest would normally use. That only the Guest should be advised in advance as to the value inserted might also allow for Guests to be more appreciative.
Unfortunately the main problem with people in general, is that no two individuals are identical in the temperatures each needs to feel hot or cold, and that also is the same within families, so a "standard" heat/cold might have to be based on ones average Guest (and when assessing how much extra or less °C Guests' used /didn't use, it'll probably average out.
One thing though, and that's please don't offer to refund Guests for what they didn't use, as the amount will be based on a specific amount, which will have been part of your overall charge. Remember, you do have an option - that you didn't use - and that's that it could have been that your Guests' had to pay for all energy used, so you have already saved them a substantial amount by including a high percentage of energy within your price for their stay!
Of course, all I have mentioned does depend upon whether one's Country allows pre-payment meters, upon Airbnb's own policy regarding payments/extra payments for energy, and also Guests' attitudes to having to pay extra for the excess heating/cooling used by them.
One comment I would add to the above is that a pre-payment meter does - at least - ensure that payment is made for the extra energy used before, Guests' depart, and it also allows for Guests' to leave earlier.
I do appreciate that different Hosts operate within a range of property types, so maybe a pre-payment meter wouldn't operate in a yurt or tent or similar, whereas one would in a bricks and mortar style property.
Whatever you decide would work best for you, just be aware that thanks to your very sensible and extremely apt question there will be many asking the same or similar questions in the coming months and years, and be grateful you asked, and for the suggestions made.
In the meantime, here's wishing you a very successful future, all the best for resolving what you asked about, and I hope that amongst what each of us who've responded to your plea, have said, there definitely will be the answer you wanted.
Cheers!
