Window AC vs Mini Split AC for My Add‑On Room: Which Consumes More Energy?

Answering this question is tricky. That’s because the power consumption of any AC depends on a bunch of different factors (like size, efficiency level, run times, etc).

But we can say that a window AC unit will typically consume more energy and cost more to operate than a similar-sized ductless mini-split AC.

In fact, according to EnergyStar, a ductless AC typically consumes about 30% less energy than any other room air conditioner. We’ll explain why window units consume more energy than ductless mini-split ACs.

Why? Well, it basically comes down to 2 factors:

1. Insulation
2. EER ratings

Window AC units typically have to consume more energy because they have poor insulation levels.

You see, window units allow a lot of heat indoors due to the way they’re installed. They’re simply placed into an open window, which allows:

• Hot unconditioned air to leak into the home
• Conditioned air to leak out of the home

And leaking air means the air conditioner has to run longer and work harder to keep the room cool.

Ductless ACs, on the other hand, use only a very small, tight hole in the wall to connect the indoor unit to the outside unit. The smaller, tighter fit means very little (if any) air leaks in or out of the home. This means the unit doesn’t have to run as long or work as hard to cool a room.

Note: To be fair, newer window ACs provide tighter fit insulation and additional window sealing features that decrease the amount of air leakage. But, overall, when compared to a similar ductless unit, a window AC is still inherently less insulated.

EER stands for Energy Efficiency Ratio. Every air conditioner has an EER rating. These ratings tell you how much cooling the unit offers per watt of electricity consumed.

The higher the EER rating of an AC unit, the more efficient it is (i.e. the less energy it consumes).

• Window ACs on the higher end of the efficiency scale have EER ratings around 12.2.
• Ductless ACs on the higher end of the efficiency scale have EER ratings around 16+.

If you’re shopping around for ac units, be sure to look at EER ratings. If you’re looking online at manufacturer sites, EER ratings are typically listed under the “specs” or product details information.

If you’re looking at a physical unit, you can find the EER ratings on the yellow EnergyGuide label on the side of the unit.