I bought one for my 18 wheeler. I bought the 50 Qt AcoPower Lion cooler, which is basically the model with a LION 180wh battery to keep it running when there is no external power. For my purposes, 50 qt is too big but it is difficult to really judge without seeing one. 50 Qt is huge.
OTOH I still love it and it allows me to carry weeks worth of my Ketovore food so I don't have to eat truck stop food.
For an RV it definitely gets in the way. I have a 19' Scamp and I just shoved it in the door and left it there. Waaaay big and waaaay in the way. I can set it up on the front 'couch' to get it out of the way but it is just big! But again, it allows me to carry so much stuff and keep it cool.
DC compressor fridges work extremely well, and extremely efficiently. I haven't personally tested it but it appears to use 40w on
eco, which is all you really need once the food is cooled down. And event then it only runs perhaps 20% of the time. So 8-10 watts average, again depending on how cold you want to keep your stuff.
I run mine at about 34 degrees, which will keep it very cold on the bottom and chilly on the top. I am buying a little dc fan to rig in it to circulate the air for more even cold distribution.