We have always kept our trailers plugged in 24/7 and barely noticed any change in our bill. Haven't looked at our rates, but we have the frig on all the time, we sometimes go out in the evening and watch a movie and just chill out. What I would consider just normal usage. Suggest you call your utility company and ask for comparison in your bill for this same period last year or two and compare. You did mention the A/C @ 65 degrees....maybe your problem. We kept ours about 75+ and if it needed to be cooler when we were out there, only takes 5 minutes of moving the thermostat and you're good. Agree about companies not reading every month or mis-reading. Ask for them to come back out and check.