For the short term I added some cheap insulation to the box and am basically using it as a ice box.

I crunched some numbers and was under the impression that the engel unit was for a much smaller box... which no doubt is one key to the energy efficiency. I may have miscalculated the size of my icebox though.

I recently moved the boat across country... and when I arrived at the new destination, I had loads of expensive work done, so refrigeration took the back burner to new rigging, new lifelines and extensive mast work (all new LED lighting).

Thus I have no real idea of the cost/efficiency of AB verses Engel, for now, I use ice.