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Portable vs Window AC Units - Why You Shouldn't Make a Cake out of Acorns

2024-03-02

I’m getting better prepared for that sweet 108 degree 90% humidity weather coming my way this summer. I was debating between types of small ACs. It seems there’s a huge difference between window AC units and portable AC units.

It helps to first understand a simplistic model of how an AC works. There are two separate coils. The condensor, the hot side, is where the heat is released outside. The evaporator, the cold side, is where cool air enters your living space.

Here’s what I’ve learned if you’re ever been interested in a portable. The Achilles’ heel of portable ACs that use a single exhaust hose is the fact that to cool the condenser coils (the hot side) it has to use your indoor air (that it already cooled) and then it shoots that air straight out the window through the hose. That’s like baking a cake, grinding up the cake to put in the batter of another cake, baking that and then throwing the finished cake at a tree.

Single-hose Portable AC [JPG]

Mechanism in Action [JPG]

This inefficient use of indoor air to cool the condenser then creates significant negative pressure in your house which results in hot outdoor air getting sucked inside through small cracks in your home at the same rate the air is leaving. Comparatively, a window AC unit instead uses outside air to cool the condenser, resulting in no negative pressure and no wasting of cooled air and cake.

Window AC [JPG]

Finally, the portable AC unit itself as well as the hot uninsulated exhaust hose act as heat radiators to even further decrease the efficiency. Window ACs keep the hot parts outside.

For a small AC, unless they won’t fit, window units are the way to go. Otherwise, there are more expensive dual-hose systems for portables. They use a separate hose to pull in outside air to cool the condenser and expel it right back outside in the other hose, solving the negative pressure problem and wasting of cooled inside air. It’s like making a cake out of the weird soft orange insides of acorns and then leaving it outside cause that’s nasty.

Dual-hose Portable AC [JPG]

Cake [JPG]

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