Mileage with A/C turned on.

My wife and I are considering purchasing the Atomic Coupe. Are there any owners out there who can give us an idea as to how quickly the batteries are drained when using your A/C. I’ve been told that outside temp and humidity variations can make it difficult to provide a solid number, but if someone has used their air while driving…say…20 miles with no problem I’d have a lot more information than I currently have. Oh yeah, and the outside temp would be helpful too. We live in Central Florida. Thanks.