I have my frig plugged into the power outlet, but only as a secondary source. A house battery addition is mighty handy for most of your power needs. I don't hesitate to run my frig for a day or two without running the engine, and cell or camera charging using 12v is a freebee. You can even purchase led light strings and operate with 12v.
I have put a few high efficiency CFL flood bulbs into clamp on work lights and illuminated the area to pitch camp on a moonless night.
Clamp em right onto the roof rack tubes and it lights up the area like a prison yard on escape night.