How to Determine Energy Efficiency in a Portable Air Conditioner

In our age of growing concern over energy cost, there is a sense that efficiency is an important factor when one is considering a new appliance. We want to get the most bang for our energy buck. Air conditioners have long been among the easiest to evaluate this, because government mandates require efficiency ratings to be made plainly apparent for every air conditioner sold.

But that doesn't mean the numbers have to be used in advertising! Fortunately, it is an easy number to come up with from data found in the specifications of a given unit.

There are two numbers to look for, the BTU output and the Wattage. The BTU rating is how much heat the unit can remove over one hour in standardized conditions, meaning how well it cools air. The Wattage is how much energy it requires to do so. The Energy Efficiency Ratio, or EER is a computed number arrived at by dividing the Wattage into the BTU rating.

For example, as you can see in the Specifications chart from the EdgeStar 12,000BTU Extreme Cool Portable Air Conditioner Product Manual, it has a Wattage requirement of 1200. 12,000/1200 gives an EER of 10. The higher the EER, the more efficiently the air conditioner operates. One thing to note is that one should check the spec sheet for the actual numbers, because occasionally, manufacturers will round the actual number up for advertising. The 12,000BTU unit you're looking at may only actually put out 11,500BTU, which will affect the EER.

From EdgeStar AP12000S-1 Product Manual

The portable air conditioner industry is not as yet subject to standards like other types are. The government last established such standards before most of us had even heard of a portable air conditioner. There are also no established criteria for Energy Star Rating in portable ac's, and they are thus not eligible for the program, so you won't see the Energy Star logo associated with a portable ac.

For more information on what qualifies as Energy Star rated, see the link at the bottom of the page. As you can see from the EdgeStar example above, many manufacturers voluntarily comply with the 10-17 EER required for other types of ac.

By nature, a portable air conditioner has a couple of strikes against it when it comes to efficient operation. The compressor (a heat producer itself) is located inside the room instead of outside, and the unit must pump exhaust air through a 5 inch duct, which has resistance and increases the work load compared to just blowing it outside like a window unit. Still, the EER numbers are usually comparable to window units, attesting to the quality of portable ac design. These are serious pieces of engineering.

The EER should be considered after making sure of adequate cooling capacity for the intended use. As stated in other articles, it's a good idea to get a portable air conditioner that is a rated for a room larger than the one for which it is intended. The EER is can then be used as a comparison tool to find the unit that will adequately cool most efficiently.

The page below gives the real scoop on Energy Star, it's the government's own requirements page.

http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/roomac/prog_reqs_ac_draft_v2.1.pdf