I am not sure from looking at web pages for Isotherm
if they use the ubiquitous Danfoss compressors, but if they do then you should also check to see if they have the smart speed controller plugin or something similar attached. This reduces energy consumption
by regulating the compressor speed (and thus the current
draw). As the startup cycle is inefficient, these systems tend to maximize the duty cycle while reducing the RPMs; so although you might have 90% duty cycle time your net energy use is minimized. I had such controllers on my last boat and something similar on this one and they do work to reduce energy consumption
but result in long duty cycles.
I am in the Caribbean
with 28+C in the boat and the water at about the same temperature. One fridge (air cooled, at 5C) and a freezer
(keel cooled, at -10C) eat up around 70A (@24V) per day at the moment, but I need to defrost the plates and the insulation
on the fridge isn't great so your usage will certainly be less. The duty cycle on the fridge is high, certainly over 75% of the time, but at reduced RPMs while the freezer
runs a lot less, perhaps about 20% of the time.