I can't speak as to how much DC power it takes to run the home-style fridge but from what I've been reading elsewhere (Monocoers site), there seems to be an ongoing problem with Norcold RV fridges catching on fire. That concern, plus the extra cost of an RV fridge, may be why your original owner installed a residential. If it's been in there awhile, it apparently must work OK with whatever DC power you have. Good Luck.
Glenn Martin 07 Monaco Camelot 42', 09 Saturn Outlook. (Norcold refrigerator).