The number you need is AMP HOURS.. for OPTIMA a Group 27 is about 60 amp hours give or take a couple.. A non-optima AGM (Cheaper) is `100 amp hours. and a flooded wet battery (Cheapest) is also 100 amp hours.
I should add weight is heavier in the non optima types as well about the same 6/10 ratio since weight and amp hours are directly related.
Finally MARINE/deep cycle like the Marine Master.. NOT THE BEST choice
DEEP CYCLE.. Like a GC-12.. (If it will fit) much better for house use.
Deka stores may have a DEEP CYCLE in the 27/31 format as well.. I DO NOT KNOW. My Deka's are G-20s (A GC-2 class) 6 volt in series.