Go big with your battery set up. I have two 104 lb, AGM batteries in parallel. Many will use the larger 6volt units in series and that works great also.
With these, I can run lights, heater, refrig, etc for days before starting my generator.
Best thing you can do to prepare, well before other basics.
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Bob and Better Half
2007 F-250 PSD, SW, CC, LB, 2WD
2006 TF32SS Cross Terrain Toy Hauler (sold)
Reese 16k slider