This question is coming up more and more from hosts who aren't EV owners.
Hosts who are EV owners know how to deal with this because we are informed on electricity rates, know exactly how much it will cost. ie not much compared to aircon, or baking a roast for 4 hours etc. And we know how to ask guests to charge in non peak hours (they will). Can't charge very fast on standard electrical circuits anyways. There is no fire risk for older houses unless you haven't already upgraded the wiring/ put in more circuits to cope with guests turning everything on at once!
I wish Airbnb would write some articles on this as I've responded at length to previous hosts on this question. But to summarise, we are in the hospitality business and we cater for guests needs. Should you as a host not wish to cater for EV chargers, you have every right to. And ask guests not to. Just make it clear everywhere in your listing. The amenity tickbox for EV chargers does indicate for guests that hosts are happy to have them and will accomodate them (and generally will not charge, as its a feature like the pool or spa etc).
Because, owning an EV is a mindset shift. Electricity is everywhere, this is not like gas which requires specialised safety storage! So EV owners will expect to charge anywhere so managing expectations is crucial. Sure, EV ownership in the US is probably less than 10% nationally, like Australia, but if your typical guest profile would be more inclined to have an EV, then you need to think about if you wish to serve this need or not. Over time as the % of EVs increases, you may be locking out a segment of the market, especially if you are in a highly visited tourist area.
Note as a EV host, I did install a charging unit that's faster than plugging into the wall socket, but no where near 'super' or 'fast' charging, I call it a 'slow' charger vs 'trickle charging' . Guests who want to super or fast charge will goto a proper charging station anyways. Also, I state BYO Type 2 cable, so guests will know its a proper charging unit and I hope it gives me an advantage over wall charging/trickle charging. I have noticed an increase in bookings due to the EV charger after 18 months FYI. I'm in a high tourist area.
Just a different perspective for the non EV hosts out there, hope this helps in your decision making with some facts
All the best,
MK