In the article at the link below we focus on choices you might want to consider. Especially before you buy a major component, cut holes, frame things in, or run wiring.
We had priorities to enable long term “boondocking” or “lot squatting” for extended periods. Perpetually in fact, without firing up a noisy generator.
We had additional concerns since we camp in desert terrain. The Southwest section of the USA. Where air temperatures can exceed 100°F for days on end. Even continuing throughout the entire night. It is not uncommon to have the interiors of closed up vehicles exceed 150°F.
We wanted to power ours off Solar and Battery. We can state we have succeeded, and have been successfully refrigerating and freezing our food for numerous years. Off solar and 2 relatively inexpensive marine deep cycle batteries.