If you are told there are 30 amp receptacles and all you find are standard household plugs, you have a gripe. If your site has a standard 30 amp female plug, you need to know a lot more before you go off and say you only have 20 amps of power available. There are a lot of appliances in an RV that will run you past 20 amps and right on past 30 amps if you turn it on. Things like hair dryers, space heaters, microwave ovens all can draw 12 or 13 amps. You could be at 18 amps on your normal stuff, go to dry your hair and trip a 20 or 30 amp service. I have never seen a park that had 30 amp hookups, yet were in reality 20 amp. Won't say it couldn't happen, but if you think you are finding it often you are either scraping the bottom of the park barrel, or are mistaken.