Danfoss and Waeco units pull very little amperage. Not much more than an absorbtion unit with auxillary condenser fans. They are very efficient.
I know when my 3 way expires (if it ever does), I'll replace it with a compressor fridge and I have a TC so limited battery power too. A small compressor fridge is about the same price as the 'Amish cooling unit' and you get the entire unit, not just the plumbing.
For me, a big plus is, they don't have to be level to work either whereas a thremosiphon unit ammonia fridge has to be level to operate efficiently and un level operation can ruin an ammonia fridge. Not so with a compressor unit.
A residential style compressor fridge is no where as efficient as a Danfoss or Warco unit. Biult for in a house with basically unlimited 110 volt power. The Danfoss and Waeco units run on 12 volt or 110.