More portable air conditioners are returned as “underpowered” for this reason than any other. The unit is usually fine. The exhaust is going to the wrong place.
Why an unvented portable AC cannot work
An air conditioner does not destroy heat. It moves it — out of the air passing over a cold coil, and into the air passing over a hot one. If that hot air is dumped into the same sealed space you are trying to cool, you have built a loop. The compressor adds its own waste heat on top, so an unvented unit in a closed space makes the space slightly warmer over time.
This is also why the unit never cycles down: it never reaches its set point, so it runs flat out all night at full draw. On battery that is the difference between roughly two hours and seven.
What good venting looks like
- The exhaust duct ends outside the cooled space — outdoors, or at minimum a separate sealed compartment that vents outdoors.
- The opening is sealed around the duct. A duct poked through a gap lets hot air and insects straight back in.
- The duct run is short and straight. Every bend and every extra foot costs airflow and radiates heat back inside.
- Intake and exhaust are not adjacent, or the unit re-inhales its own hot exhaust.
Pick the kit for your setup
Van conversions
A window venting kit cut for your van is the cleanest answer — available for Mercedes Sprinter, Ram ProMaster and Ford Transit. The panel drops into the existing window opening, so there is no cutting and nothing permanent. If your van is not one of those three, the universal DIY kit lets you cut a panel to fit, with or without the cutting tool.
Tents
The tent venting kit seals around the duct where it passes through the tent wall. Versions differ between Mark 2 and Mark 3 because the duct diameters differ — they are not interchangeable.
Boats
The dual-duct marine window kit suits hatches and is built for the damp.
Renting, or not cutting anything
The universal window seal cloth is a zippered fabric panel that seals an open window around the hose. No drilling, packs flat, and it comes out when you leave.
Permanent installs
- Mounting kit — a 22 lb appliance sliding around in transit is a hazard.
- Hose insulation — stops exhaust heat radiating back through the duct wall into the cabin.
- Duct adapters and replacement ducting — for routing air where a build needs it.
- Cold air splitter — feeds two bunks or two rows from one unit.
Five-minute checklist
- Does the exhaust end outside the space? If not, nothing else matters.
- Is the opening sealed around the duct, not just poked through?
- Is the duct as short and straight as it can be?
- Can the intake pull cooler air from somewhere other than the exhaust?
- Is condensate draining somewhere sensible?
Get those five right and a correctly sized unit will hold temperature and cycle down. For sizing, see what size portable air conditioner do I need; for runtime, how long it runs on a battery.
Specifications are the manufacturers’ published figures. Runtime and solar estimates are arithmetic from those figures with the assumptions stated, and will vary with insulation, outside temperature, shading and set point.