@Verna39,
We charge for electricity usage for long-term rental of our spaces, and have it stated in the listing details :
Longer term stays (28 nights and longer) will pay for electricity. Each space has its own meter, and we charge only for what is actually used at $0.35 per kwh. A deposit of $10 per night will be collected via Airbnb payments system prior to check-in. Guests will be refunded any unused amounts at checkout.
It is within Airbnb policies to charge for services not covered in the nightly rate. The transaction just has to occur via Airbnb's payment system.