The Energy Guide sticker may not tell the whole story!
What is a Portable A/C?
Portable air conditioners have become increasingly popular over the last few years. Like any other A/C, they capture heat energy from the home and dump it outside. Instead of hanging out a window, these units sit fully indoors and discharge hot air through an exhaust hose. But if they work the same way, then how are they worse?
How A/C Works
Simply speaking, air conditioners have two sides: a hot side (the condenser), and a cold side (evaporator). The hot side sits outdoors, and the cold side sits indoors. The heat is captured and stored on the cold side, then pumped to the hot side to be released. Fans blow air over each of these sides to help capture or release heat.
There is no air exchanged in this process. Outdoor air blows over the hot side, and indoor air blows over the cool side, but air doesn't enter or leave the home.
Portable air conditioners send air outside, not just heat.
Why Portables are Different
Both the hot and cold sides are located indoors with these units. Since there is no outdoor component, it needs some other way of releasing heat outside. To do this, it draws in house air (which it has just cooled) to cool the condenser, and then dumps that air outside. If that sounds inefficient, that's because it is.
Air Exchange Matters
Normal air conditioners don't add or remove air, which means they don't change the air pressure in your house. Since portable A/Cs are sucking up house air and exhausting it outside, they are effectively de-pressurizing your house. Air has to come from somewhere to replace what was exhausted, and balance out the pressure. So where does it come from? Outside, where it's hot.
Hot outdoor air leaks in to replace what the unit exhausts.
Extra Heat
Mechanical systems like fans and compressors can produce a large amount of waste heat when they operate. In most systems, these hot and loud components are located on the outdoor (hot) side. All the extra heat they generate is simply released outdoors. With portables, everything is indoors, so that extra heat is added to your house.
Efficiency
Here is a direct comparison of the power consumption of a window and a portable unit. Both have the same cooling capacity and are made by the same company, but one is portable and the other is a window unit. As you can see, the portable unit uses 60% more power to achieve the same cooling.
Tech Specs
Does this seem hard to believe? Here are screenshots from the manufacturer's website comparing the two units.
Why Buy a Portable?
We've established that portable units are less efficient. However, they do have a number of advantages.
Portable (of course), can be moved to different rooms.
Easy to install.
Don't block the window.
Better looking.
Any appliance is a combination of features that the buyer feels will work best for them. There are always tradeoffs. Hopefully this has given some additional clarity to what those tradeoffs might be!
Key Points
Both the hot and cold side sit indoors in a portable unit.
Conventional A/C does not remove air from the house, portables do.
They use 60% more power for the same cooling.
They are louder, and less efficient, but they are easier to install, and don't block the window.
There are tradeoffs to any appliance you buy.