Summer before we spent a month at a campground in Colorado with our 5th wheel, where the monthly rate did Not include electricity. At the end of the month at check out, they read my site electric meter and we owed them $46 which meant we had used $1.53 of electricity a day on the average. This was running the roof AC everyday and some nights, plus heating domestic water, running the fridge, lights, TV, etc.
I highly suspect most campgrounds add in considerably more than $1.53 a day to their short term rates for electric sites. As long as they don't show electric cost as a seperate cost, they can charge whatever they wish and that the market will allow.