I use batteries and inverter to power my house. I also took a road trip this summer and bought 2 deep-cycle marine batteries for the RV. I found that the cheap inverter I purchased worked fine for the trip. It worked better attached directly to the batteries than through the lighter plug. This was due to smaller wires used to go from the battery to the plug outlet that would not sufficiently carry the load.
The batteries are heavy but they can be charged as you drive. If it is sunny you can have a solar panel charging and supplying your electric needs. Go for a larger battery to lengthen the duration of use. Less than 100 for the battery at most RV stores and Sears, etc.
There is usually AC around as was said but in a pinch this should work for you.
- Brian