I did RV this year. we brought our own generator, so I don't have first hand experience w/ the pass from roo. Just bring your own fuel for it and run it whenever you want, they don't have people going through the campgrounds making people turn their generators off. We had AC whenever we were at camp and ran the fridge the whole weekend. We had a 4k watt generator and burned maybe 20-24ish gallons of fuel?
Also did RV for the first time. I don't remember the exact fees but I do remember thinking you could buy a generator for what they were charging for power hookups. We brought our own generator to save the money. Everything was great until I went to start it on Sunday morning (by far the hottest day) and the starter cord broke. A short YouTube video later and a couple beers and we had that sucker running again. Shoutout to the camper who taught me it's easier to get the rope through the handle by torching the end of it with a lighter.
Skip the power hookups unless you just have money to burn. Most of those sites were empty this year. Plus they were closer to the I-24 and a little farther walk from Centeroo.
I'm going to be the Devil's Advocate here...while I've never taken an RV to Bonnaroo here's why I like having power provided: 1. The noise levels. All generators make noise, and some of them are obnoxiously loud. Now multiply that by large numbers and it's quite a racket. 2. Exhaust smell. Most RVs blow exhaust out a pipe on the side and usually right into your campsite. 3. Heat generation. Generators run hot, and can heat the inside of your RV making cooling harder. 4. Most important: Generator Carbon monoxide production. If many are running in a concentrated area you'll get enough CO that you'll start hearing RV CO detectors going off.
So it might be more cost effective to not pay for a power option, but it makes for a nicer camping experience. OK I'll get off my soapbox now.