@Rosalind98
I think it is perfectly reasonable to ask guests not to run air-conditioning on full mode when they are out of the apartment, especially if you have an energy saving mode that they can use to keep it cool enough for their return. Many hosts ask guests not to run it at all when they are out.
However, it is a bit tricky to start making these kinds of requests after a stay has begun and you never know if the guests will get a bit touchy about it given as it's an observation of their behaviour when you unexpectedly had to enter the space.
The best thing to do is to state these things in your listing description and particularly in the house rules, so that it's something the guest should not only be aware of, but are agreeing to, when they book. Of course, a lot of guests won't read the information or necessarily follow it, but once it's in the house rules then you are well within your rights to politely remind them if they are ignoring it.
I do find it helpful to mention these things in the context of being environmentally friendly. I am not sure if you do an in-person check in, but this is the sort of thing I would bring up again at that stage. Air conditioning is not an issue here, but heating is, and leaving on lights when not in use is an issue everywhere. I say something like, "We try to be an environmentally conscious household, especially given the current energy crisis, so it would be great if you could please remember to turn off lights when you leave the house."