I bought two in a package at Costco. I installed one in our house. Quite a job due to the very large size of the thing, just barely fitting into the electrical outlet box. Connection screw for only one black, one white and one safety ground wire, so Marettes and pigtails were required to hook it up in the middle of a multi outlet run, leaving barely enough depth for the big outlet. I doubt if I will install the second one - certainly not in the RV. Green LED stays on all the time.
They say a GFCI uses $3 of electricity a year. I bet this thing does as well. It adds up, especially if you have a couple of arc interrupter breakers using $5 a year as well.