Cooling an RV or camper

Everywhere else on this site, running cost is measured in cents and the answer is usually “it barely matters”. In a camper off hookup, power is a finite store you are also using for the fridge, the water pump and the lights — and that reframes the whole decision.

Here is the same table that reads as trivial for a house, read as a camper.

In a house, the gap between the top and bottom rows is a few dollars a month. In a camper it is the difference between a full night’s airflow and flattening your bank before midnight.

That is why the answer here is a fan, and why the fan question is mostly about where its energy comes from.

• A tool battery. Separate from the house bank, swappable, chargeable while driving, and it publishes a run time. Nothing you do with it affects the fridge. This is the cleanest answer for extended off-grid use.
• The 12V system directly. Efficient — no inversion losses — but it draws down the bank you need for everything else, and a fan running all night is a meaningful share of a modest system.
• An inverter and a mains fan. Gives you access to quiet, efficient DC tower fans that publish dBA, at the cost of inverter conversion losses and the inverter’s own idle draw. For a 2.9 W fan, that idle draw may exceed the fan itself.

The last point is worth pausing on. A fan drawing 2.9 W on low is wonderful in a house and slightly absurd through an inverter, because many inverters consume more than that simply being switched on.

A camper is a small, thin-walled, largely uninsulated box with a lot of glazing, parked in the open. The free measures matter more here than in any building.

• Park in shade, and think about orientation. Which way the largest window faces at 3pm changes the interior temperature more than any fan will.
• Cover the windows. Reflective screens on the windscreen and side glass are the highest-value item in the vehicle for this. External covers beat internal ones for the same reason they do in a house.
• Open the roof vent. Hot air collects at the ceiling in a van exactly as it does in a room. A roof vent lets it leave by itself.
• Create a path. One opening low on the shaded side, one high on the other, and the stack effect does work for free. Then a fan increases the rate. Placement for cross-ventilation.
• Purge on arrival. The air inside a van parked in sun is far hotter than outside. Replacing it takes minutes with real airflow and is the fastest improvement available.

A roof-mounted RV air conditioner on shore power is a real and effective option, and it is what those units exist for. It is outside what this site covers — we work from certified residential data, and RV units are a separate category with their own ratings.

A domestic portable air conditioner in a van is a poor idea on three counts. It draws roughly 1,300 W, which no practical battery bank sustains overnight. It needs its exhaust ducted outdoors, which in a van means a purpose-cut panel in a window or vent. And its rated capacity is well below its headline figure — 9,500 BTU SACC from a 14,000 BTU box.

An evaporative cooler works in a dry climate with the vents open, at 220 to 250 W. That is marginal off-grid but plausible with solar and a decent bank, and it is a genuine temperature drop rather than felt cooling. Only where the air is dry, and it means carrying water.