How to power fridge/freezer at night when not working?

What sort of system should I employ to keep my fridge and freezer running at minimal power overnight while we're not in service?  I'm rigging up everything on an old school bus and have yet to figure out how to keep these 2 going safely overnight.  I can't park at my commissary bc the door to their yard is too short for me to get through and the rv yard i keep the bus at now doesn't have power hookups i could tap into.

looks like its going to be a gen set.. unlesss you can get a inverter big enough, but for just the fridge and freezer a simple 120 volt, 20 -30 amp should be enogh power for those.

theres no way your going to want to run a genny all night long to power the fridge and freezer..... 
like buck said, any way you can get a tap off of an electric source??
if not, i would look into a battery bank and inverter set up..... will be a bit pricey to do that right, but would work great for what your saying you need it for
 
just off top of head, 3 29 series marine deep cycles, and a small inverter to match power needs, after swapping to batts for the day never open the doors, should be good for around 10 hours(overnight) if all you are doing is keeping them at temp and not trying to bring down to temp, tap off your genny during the day to recharge the batts, rinse, repeat........
 
should be more then enough to keep you cold over night and possibly a little extra left over for emergencies......
thats a "get you in the ballpark" idea, would need to know power consumption, ambient temps, etc... to dial it on real needs
should be easily doable for under a grand....... and if well maintained, and you never suck batts below 50%, should be trouble free for a good three years or so before batts will need replacing.....
so your looking about 360 bucks a year (roughly 30 bucks a month) to have that sort of system set up....
your looking roughly a dollar a day until batts need replacing, you will be 6 times that amount if not much more trying to run a genny all night, plus i doubt a genny will last more then two years being run day in and day out like that 
 
just noticed your in jacksonville, you may need more, or bigger batts at least during the heat of the summer, but it can be done safely, and fairly cheap still.......being in florida you should have a wealth of knowledge close by..... go to any marine electrician and he should be able to tell you just what you will need ........ just dont buy from him, lol......
piece the system together from NON marine outlets and save tons of money
 
hope this helps !!!..... i have always said there is a close relation to big boats and food trucks