@Angie458 i honestly feel for you I had long term guests who update her booking every 2 weeks after more than 2 months booking I end up having an electricity bill of 800 for her stay. And I had warned her about the usage of the heater but was a waste of time.
My advice is to tell guest u can cover heat/gas till a certain amount of money if the bills go over that u will ask via resolution centre for extra fees payment otherwise it is not worth hosting if expenses are hight than the income. But call Support also for their advice on that. I have learned now never to accept more than 2 weeks booking and not to accept any renewal I had guests who want to renew 2 times for 2 weeks I simply said I prefer not. They get too comfy and bills sky rock. In Australia, u cannot win when too warm Air-cond is on all day long and when winter Heater is on all day none stop and unfortunately in a country where electricity is very expensive.