We were on a dry site last year and had 2 visitors, each using CPAP machines. My camper at the time did not have a 12V plug and I don't know if the machines had 12v.
I have 2 batteries and a 750W inverter w/ 2 120v outlets (about $40 on sale at Harbor Freight). Brought a battery inside w/ the inverter, hooked up both CPAPs and powered each all night. Charged battery next day on my generator and they were set for the next night.
2015 Shamrock 231KSS, Oyster shell
2016 Chev Silverado LT Z71 Ext. Cab, 4x4, 5.3L V/8
Reese Straight Line WDH, 2000W Honda Gen.
2 Old Town kayaks & 2 Boston Terriers - Zoey/Gonzo
Lar & Ruth
55 nights camping in 2015, 45 in 2016