Understanding Energy Efficiency Ratios for Portable Air Conditioners Can Save You Money!

Each air conditioner has an energy efficiency rating that lists how many BTU's per hour are used for each watt of power it draws.

1. What is EER?

For room air conditioners, this rating is the Energy Efficiency Ratio, or EER. For central air conditioners, this rating is the Seasonal Energy Efficiency Ratio, or SEER.

These ratings are posted on an Energy Guide Label, which must be attached in a visible place on all new air conditioners. Many AC manufacturers are voluntary participants in the Energy Star labeling program. Energy Star labeled appliances indicate that high EER and SEER ratings.

2. How is EER calculated?

The air conditioner EER is its British thermal units (BTU) rating over its wattage. For example, if a 10,000-BTU air conditioner consumes 1,200 watts, its rating is 8.3 (10,000 BTU/1,200 watts). The higher the rating is, the more efficient the air conditioning unit is. However, a higher rating is usually accompanied by a higher price.

3. Would the higher portable AC EER rating be worth the extra cost?

Let's say that you are given a choice between two 10,000 BTU air conditioning units. One has an EER of 8.3 and consumes 1,200 watts, and the other has an EER of 10 and consumes 1,000 watts. Let's also say that the price difference is $100. To calculate what the payback period is on the more expensive unit, you need to know:

  • Approximately how many hours per year the unit will be operating
  • What the rate of a kilowatt-hour (kWh) is in your area

Let's also say that you plan to use a room AC in the summer (approximately five months a year, depending on where you live) and it will be operating around eight hours a day. Say that the cost of a kilowatt-hour in your area is approximately $0.10. The difference in energy consumption between the two units is 200 watts, which means that every five hours, the less expensive unit will consume 1 additional kWh (and therefore $0.10 more) than the more expensive unit.

Assuming that there are 30 days in a month, you find that during the summer you are operating the air conditioner:

5 mo. x 30 days/mo. x 8 hr/day = 1200 hours 
[(1200 hrs x 200 watts) / (1000 watts/kW)] x $0.10/kWh = $24.00

Since the more expensive unit costs approximately $100 more, this means that it will take about four years for the more expensive unit to break even.

4. Can I trust BTU ratings?

Buyer Beware! Not all BTU ratings can be trusted. Just because the BTU's are stated to be high on specific models, this does not mean it is necessarily true. Some manufacturers will exaggerate the BTU's on units to raise the possibility of selling them and others will be more conservative to cause lower EER ratings, so keep in mind that a low room air conditioner EER may be misleading.

It is best not to allow the energy rating to be your only criteria for choosing an air conditioning unit. Research the unit you are considering for your home and you will be happier with your purchase. Here you'll find a helpful Portable Air Conditioner Buying Guide.

5. What are the benefits of EER Ratings?

Products with a higher EER rating can save consumers money in the long run. In places like offices and businesses, where appliances are constantly running, ratings can translate into huge savings over a short period of time. Portable ACs can be used in both the home and the office, including larger commercial settings, to ensure both home and business owners engage in energy efficient cooling.


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