New, larger, absorption-type RV refrigerators don't have a DC power option because they take too much power for that to be practical for battery
option, and enough to be a potential problem to supply from the tug. I don't know whether the manufacturers assume everyone takes only short drives from campsite to campsite (no cooling during the drive), or they assume the unit is in a motorhome with either propane
turned on or AC power available, but they seem to think that DC operation is unnecessary.
There is the propane option... enough said.
There is also the AC option: in a motorhome, an inverter can be mounted under the hood (with nice short input power cables for the high DC current flow), with AC wiring to the refrigerator (ten times the voltage means one tenth the current and thus reasonable wiring). Unless you want to rig a AC power cord from tug to trailer (an interesting idea, but not a common one...) then this means an inverter in the trailer, and lots of DC power from tug to trailer... which is back to the original situation that someone decided not to provide for in the refrigerator design.
I wonder what Dometic says to do?
I think the ideal in some ways is a high efficiency unit, as Ted described.