Using an air cooled 12V unit... If you have a perfectly sealed, REALLY well insulated box, (= vacuum
panels or 7" of foam)... of reasonably small volume, (like 2 cu ft), your Ah/day
consumption might vary from 15 to 25 Ah in cooler months, to 30 or 40 Ah/day in the heat of a tropical summer. (100+ F)
The folks who have huge power
consumption in the summer, usually have too large and too poorly insulated a box, with a poor fitting lid. (unsealed OLD foam looses its
insulation value). They may also have the compressor in a tight space with no muffin fans for ventilation, or locate it in the hottest part of the
hull.
The time and
money invested in making your
refrigeration efficient, is
money well spent, and will pay for itself in short order. It is the lions share of your anchored out energy demand!
M.