What You Don't Know About Portable Air Conditioner Efficiency

Portable air conditioners are a convenient method for providing supplemental or primary cooling in situations where the central air system is ineffective or a window air conditioner is impractical or prohibited. Unlike a window air conditioner, the portable version offers built in mobility for flexible installation and easy off-season storage.

But comparing the efficiency among portable air conditioners can be tricky because they are not subject to Energy Star guidelines (much like small space heaters) and the efficiency information provided by the manufacturer or retailer is sometimes incorrect.

1. Don't bother looking for the Energy Star label on portable air conditioners.

The Department of Energy, for unspecified reasons, states on their website they don't offer Energy Star ratings on portable air conditioners at this time.

2. Use the EER Instead - But Watch Out

Although Energy Star ratings are unavailable for portable AC's, the next best measure of energy efficiency is the Energy Efficiency Ratio (EER) which measures how many BTU's per hour are used for each watt of power a particular unit draws. An EER rating of 10 or higher is considered above average.

The EER number can usually be found in the product description or specifications, but even when it is available, it is sometimes incorrect. The most likely reason for this oversight is human error since the EER number is mistakenly under-stated as often as it's over-stated across a wide spectrum of brand names.

However, you can easily verify the EER of any portable air conditioner by dividing the number of BTUs by the wattage found in the product's specs.

For instance, the Whynter 14,000 BTU dual hose portable air conditioner consumes 1250 watts which works out to an above average EER of 11.2 (14,000/1250 = 11.2). Also, if the EER is NOT stated in the product description you can easily figure it out for yourself using this simple formula.

3. Cost to Operate a Portable Air Conditioner

As a group, portable ACs are surprisingly cheap to operate with hourly costs ranging from 10 cents per hour for compact 8,000 BTU models on up to 15-17 cents per hour for the large 14,000 BTU capacity models (based on a rate of 12 cents per kWh).

Although the cost to run is reflected in the EER - higher EER = fewer watts per BTUs - it can't hurt to know how much any given unit will cost to run.

If you know how much your local energy company charges per kWh (it's on your electric bill) and the appliance's wattage (from the product specs) you can figure out the cost to run just about any electric appliance with this simple formula: Watts x.001 x Cents/kWh = Cost To Run Per Hour.

Here's how the formula would look for an 1100 watt portable AC running at 12 cents per kWh: 1100 x.001 x.12 =.132 or 13 cents per hour rounded off.