I will preface this saying I don't do many mobile details because I HATE them, however I have never had a customer even bat ane ye when I tell them I will use their water and electricity. That being said I do tell them up front before I get there since I wouldn't want to show up and find out that they don't have exterior outlets or anything.
I have never seen the point of spending the extra money and getting a vehicle big enough to have the water tank and generator. Seems like unneeded overhead to me. I don't go to peoples offices, so I just can't think of a situation where I would need to have all that with me.
Also she is obviously a pain in the ass since she asked for $40 back. You could have detailed cars there for a whole weekend and not used $40 worth of water and electricity. I would have left right when she threw a fit about the power. I don't deal with customers like that. They can call someone else if all they want to do is complain.
I've said this a lot, but it's just not possible to get every car totally clean with waterless washes. If the car isn't filthy thats one thing, but most cars, especially before a correction, need some water pressure to get all the grit and grime out of cracks and crevices. Just my .02
However I understand that you said "most" just saying it doesn't work for all cars, and in my experience not most either. I am amazed at the amount of crap that comes out from behind moldings and in body cracks when you use a pressure washer on them.
That post doesn't make much sense. he didn't ask to use her towels and soap he asked for electricity and water. I built decks in a pervious career and we ran our air compressor and all of our tools off the owners electricity for months sometimes. Also used their water to mix the concrete for footers. And never once did anyone complain. They would rather that than running a generator all day long..
some people just want to ##### and moan no matter what you do for them.