Hi @Maria19875 ,
Do you advertise that you have an EV charger in your listing? I assume so. I have an EV but don't list that we have one on our property, but if I did, I'd add it as an amenity and would not charge them an added fee.
One way you could do this is by adding what it costs to charge an EV to your nightly rental cost. Not only will you get a bit of extra $ each stay for any guest not using it, but the last thing a guest wants is any added surprises.
That's how we would go about this.