Portable AC Energy Efficiency

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Portable AC units provide one large benefit: they’re all-in-one fully portable AC units.

The one major downside of this all-in-one portable design is that the AC system’s cold and warm components are all housed right next to each other in the same compact appliance located inside the room the air conditioner is actively working to cool.

The warm components absolutely need to be cooled.

Which is why a portable AC system takes cold air from the room it’s actively working to cool, and blows that cold air over its warm components, through a duct, and out of the room.

This process cools the AC’s warm components but it also makes the portable AC system itself highly inefficient:

1. the air that cools the system’s warm components naturally heats up. This hot air travels through ducting to the outdoors.

The problem here is that it heats up the ducting as it travels through it.

The duct itself is usually

  • a large diameter – at least 5 inches
  • and made of a cheap thin plastic

Both of these factors allow the ducting to readily radiate heat back into the room the portable AC unit is actively working to cool.

2. the exhausting of this hot air also creates an area of low pressure inside of the conditioned room. Whether the air is hot or cold really doesn’t matter – the fact is that air is being removed from the conditioned room and this creates an area of low pressure inside of it compared to hot outdoor air.

This pressure gradient causes hot outdoor air to get pulled into the room.

Any gap, any hole, any crack between the portable AC unit’s window kit and the outdoors allows hot outdoor air to infiltrate the conditioned room.

Areas of concern

These two inefficiencies leaves us with several “areas of concern” when it comes to portable AC efficiency:

First, around ducting

  • the duct itself
  • where ducting connects to the AC unit
  • where ducting connects to the window kit

Second, around the window kit/bracket

  • the top of the window kit
  • the bottom of the kit
  • the sides of the kit
  • the gap between the moveable part of the window and the stationary part of the window


  • the size and number of windows in the room
  • how well the room is sealed

Also heavily impacts overall efficiency.

All of these areas provide a means for

  • heat to be radiated into the room (ducting, windows)
  • heat to be directly transferred into/back into the room

Improving efficiency

Use included weather stripping

So, how do you combat these inefficiencies?

The first option is to use parts included with the portable AC unit itself. Most units on the market today come with a weather stripping kit.

However, you should be aware that some models, like the NewAir NAC14KWH02 and Whynter ARC-14S, do not come with any weather stripping at all.

Some models, like the Honeywell HL14CESWB, only come with the absolute minimum number of pieces you may need.

Other models, like the LG LP1419IVSM, come with an extensive kit that comes with a many different pieces and different sizes of pieces.

In any case, even the most bare bones kit will include weather stripping and foam pieces for

  • the top of the window kit
  • the bottom of the kit
  • the sides of the kit
  • the gap between the moveable part of the window and the stationary part of the window

Installing this weather stripping will greatly reduce air gaps for infiltration air to be able to be pulled back into the room from the outdoors.

The downside of installing this weather stripping is that it makes the installation a little more permanent than it would be otherwise.

Buy weather stripping separately

If you buy a model that doesn’t come with weather stripping, you’ll have to buy it separately.

If you’re unsure how much and which type to buy, install the window kit for that specific model in the exact window where you want it installed and then measure the gaps between the kit and the sides/bottom of the window. This will determine which type and size weather stripping that you’ll need.

For reference, the weather stripping included with most models is usually some combination of

sponge adhesive weather stripping in different lengths

intended for the sill, lower rail, jambliner

foam non-adhesive weather stripping in different lengths

intended for the gap between the moveable and stationary part of the window

Most pieces are between 1/8” and  ¾” thick. The foam piece is usually thicker while sponge pieces are thinner.

Insulating ducting

In order to insulate ducting, you not only have to worry about insulating the

  • the duct itself

But you also need to insulate

  • where ducting connects to the AC unit
  • where ducting connects to the window kit

For these last two areas you can use tape to stop up air gaps.

For the duct itself you have a few options:

you can use a hose cover

All ducting for all portable AC units on the market is just about the same size - about 5 inches in diameter. Thus, hose covers are not model specific.

The universal hose cover made by Delonghi, for example, should fit any ducting for any model on the market.

you can use “bubble wrap” insulation

You can use something like this Reflectix insulation to wrap around the hose and then tape it in place using standard duct tape.

The actual R-value for this type of insulation is a hotly debated topic. Regardless, it’s really the only type of insulation that’s viable in this specific type of installation - in which the ducting is fully exposed in an indoor environment. Otherwise, standard fiberglass insulation would be the clear choice (it’s not because of health concerns).

Reducing heat radiated through windows

As a final measure to improve a portable AC unit’s efficiency, you can install solar film in your windows. We specifically recommend Gila solar film for this task.


Improving portable AC efficiency as we described above isn’t a mandatory part of installation. You can install a portable AC unit and it can work quite well without any insulation at all.

That being said, doing your part to improve a portable AC unit’s efficiency (i.e. adding insulation) does make a big difference. Keep in mind that it will not only improve energy efficiency, but it will also improve the overall cooling performance of the AC unit.

In other words, if you improve a portable AC unit’s efficiency, it will not only give you more bang for your energy buck but it will also allow the AC unit to cool the room faster – every single time the temperature in the room rises.

Our general recommendation is this:

Highest priority

install some form of weather stripping at a bare minimum

this is very easy to do, especially if it’s included with the AC unit

tape up any remaining air gaps

again, something that’s very easy to do and you should already have some duct tape lying around the house

Lower priority

insulate ducting

here costs are either high (it’s at least approx. $50 for a hose cover) or installation is tricky (installing bubble wrap insulation). Note that insulating ducting is a higher priority if you buy a dual hose unit since you get double the benefit with two hoses instead of one.

install solar film in windows

this is a higher priority if rooms are west-facing or if there are a lot of large windows in the room. Otherwise, you should be fine simply closing blinds/curtains.

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