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Many vandwellers are snowbirds, following mild weather. One major reason for this is heating and air conditioning with solar power are prohibitively expensive.
Heating is usually done with propane heaters.
Cooling is usually done with roof vents, like the Fantastic or Maxxfan. [hvac:cooling#evaporative_coolers|swamp coolers]], can also be used in deserts or other areas with low humidity.