Being an extreme hot/cold weather camper myself, I may be able to offer some help…
Part of this depends on the environment you’ll be living in. In low humidity areas, a direct type swamp cooler is the best choice. In humid areas, an indirect type of swamp cooler is better. If traveling, the indirect type will work anywhere, just not quite as well in low humidity areas. Swamp coolers just use water, so no ice is needed, although some people do add ice. I use the indirect type myself, and it can keep my van too cold, even in direct sunlight, anywhere in the USA. My biggest problem is that it has no thermostat so I have to cycle it on and off manually to keep it from getting too cold, even on it’s lowest setting. On low it uses just under 1 amp @ 12vdc, and on high it uses just under 2 amps. Basically you’re just running a fan and a fountain pump that uses so little power it’s negligible.
I totally disagree that peltier power uses too much power or is somehow inefficient. A friend has a peltier powered air cooler which is energy efficient enough for him. I also have multiple peltier powered items that I love. Peltier powered items have more than a few advantages, for one they usually have a thermostat of some sort, and two, they can also be used for both heating and cooling. While these items draw 5.25 amps @ 12vdc when the peltier is on, and they don’t draw anything when it’s off. The peltier chip itself only runs maybe 1-2 minutes out of every 15-20 minutes, so we’re talking under 5 amps for 10 hours of run time. This is thanks to the thermostat, which also keeps a nice even temperature for both heating and cooling.
The peltier powered food coolers are a totally different animal. Instead of heating/cooling water in a closed loop, they are trying to cool air in an enclosed box. The ones I’ve seen don’t have thermostats, and they run constantly, so they would use about 5 amps @ 12vdc per hour. While this really isn’t noticeably more than the 12v compressor type fridges, their usability depends on the ambient temperature. This is where peltier power gets it undeserved poor reputation. If used as intended, they are actually more energy efficient, and have a much longer life span than the 12v compressor fridges, and for a fraction of the cost, but they are meant to be used in comfortable surrounding temperatures, not a closed up extremely hot vehicle. Even the 12v compressor fridges struggle with those conditions, and neither are the best choice for campers.
I have peltier powered heating/cooling seat cushions, and blankets, and I love them. I have seat cushions for my drivers seat, my work/lounge seat, and one on top of my mattress like a mattress pad. I have one of the blankets on my bed, and another to snuggle with in my work/lounge chair. These alone can keep me comfy in any temperature, even extremes, but I use additional heating to keep the whole van comfy and above freezing if it’s extremely cold, and my swamp cooler in extreme heat to keep the whole interior cooler. I don’t want the additional things in my van either melting or freezing due to extreme temperatures.
Used properly and intelligently, I think the peltier’s are a great and worthwhile technology. The same goes for swamp coolers.
"Opportunities are everywhere, but only action makes it happen." ~ Van_Dweller