Just a bit confused on your description and not sure if you mean an RF or an FM model. So here goes a mouthful:
If it's an FM70, yellow poly plastic case, nearly a meter long and not very high, I can tell you mine uses a whopping 50+ Ah per day. Compared to my now sold engel mt-45 at 20Ah per day and my waeco cf50 at 15Ah per day (all figures with internals set to aprox 2 degree's). The FM70 had the BD35 and its power consumption as can be seen above is very high. They changed to a grey poly coloured unit and moved away from the BD35 to use their own, no doubt chinlese version of compressor. I cant answer the power consumption on the grey unit, but suspect similar. 2 x 100ah batteries and a 120w solar panel in good sunshine only just managed to keep up with the days draw.
If the one you are looking at is the white fiberglass unit, I believe they made an 80 and a 60L version, then that is a different proposition and I suspect will be nearer the engel I quoted above. I am of the opinion the high consumption of the FM70 is due to its limited depth, but long length. I am also led to believe the similar yellow poly units, the fm50 and fm95 dont chew electrons like the fm70. Again, I reckon its because these have high depth, low length.
While we are on it, the first gen engels were high in current draw (2 fold) compared to the new gen ones. But don't get confused with amperage and power. Power is the amount of amperage drawn over a period of time (hence I used the unit of Ah and 24 hours). If a fridge draws 5 amps but only runs for half the time as one drawing 2.5A, the power consumption will be the same.
2 x 100 Ah bats and a 160W panel in good sunshine should replenish any fridges power needs easily. When the sun don't shine, that's when the problems arise.