Well it is rated at 10.7A at 14 VDC and the pair of 27s should be good for about 65 AH (50%) so 6 hours ?
OTOH a
Coleman 40qt Power Chill (Peltier) pulls about 4 amps. I use one of these in transit and until the fridge cools down on shore current or propane. My GC2s are good for about 26 hours (50%) and the 200W solar (12.5A @ 75%) is enough to run the cooler and charge the batteries.
After quite a bit of study I could not find anything with as much capacity that would fit my rear compartment as 2 GC2s.
ps with my rig there is no limit to how long I can dry camp. Do use a 2400W gen to run the AC.