Ed,
Contrary to popular belief, these refrigerators aren't that thirsty for  
electricity. Most only draw 3 amps under load and don't necessarily run all the  
time. 3 amps over a 10 hour sailing day is only 30 amp hours from your battery  
bank. I currently have 160 amp hours available with two batteries. Now, this 
is  all "in theory" and we all know that real life can be different.
 
Rummy