I am using the Power Grip - Voltage Protector - 30Amp. It does not show the voltage, only lights to indicate an issue. I have used it many times at various campground with A/C on and had no problem. The campground power at my site only, cut off and I had to reset by turning power off and on again at the pedestal. I will try this again at another campground in a few weeks, just want to make sure my rig is ok before a long summer trip. I think it was a problem with the campground pedestal but want to be sure. Thanks for all you suggestion, I will check them out.