What is an energy efficiency rating (EER) in a portable air conditioner? Each air conditioner has an energy efficiency rating that details how many BTUs per hour are used for each watt of electrical power it draws.
For room air conditioners, this rating used is the Energy Efficiency Ratio or EER. For central air conditioners, it is the Seasonal Energy Efficiency Ratio (SEER). These ratings are posted on an Energy Guide Label, which must be attached in a visible place (usually on a sticker tag) on all new air conditioners.
Many portable air conditioner manufacturers are voluntary participants in the EnergyStar labelling program. EnergyStar-labelled appliances mean that they have high EER and SEER ratings.
How is EER Calculated?
The EER of an air conditioner is its British Thermal Units (BTU) rating over its wattage. For instance, if a 10,000-BTU air conditioner consumes 900 watts, its EER is 11 (10,000 BTU/900 watts). A higher EER means that the portable air conditioner is more efficient. However, normally an air conditioner with a higher EER is accompanied by a higher price tag.
Is an air conditioner’s higher EER rating worth the price?
Let’s say that you are given a selection of two 10,000-BTU air conditioners. One has an EER of 8.3 and consumes 1,200 watts, and the other air conditioner has an EER of 10 and consumes 1,000 watts. Let’s also say that the price difference is $50.
To calculate what the payback period is on the more expensive unit, you need to know:
- About how many hours per year the air conditioner will be operating
- What the rate of a kilowatt-hour (kWh) is in your area
Let’s say that you plan to use the portable air conditioner in the summer (approximately four months a year, depending on where you live), and it will be operating about 7 hours a day. Let’s also 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 air conditioner will consume one 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:
4 mo. x 30 days/mo. x 7 hr/day = 840 hours
[(840 hrs x 200 watts) / (1000 watts/kW)] x $0.10/kWh = $16.80
Since the more expensive unit costs approximately $100 more, this means that it will take about six years for the more expensive air conditioner to break even.
Are these portable air conditioner EER ratings trustworthy?
Just because the BTUs are stated as high for a specific air conditioner, it is not necessarily true. Some air conditioning manufacturers will exaggerate the BTUs on units to raise the possibility of selling them, and others will be more conservative in regards to BTU, which will cause the portable air conditioner EER rating to be lower – so a lower EER may be misleading.
It is best not to allow the portable air conditioner EER rating to be your only criteria for choosing the best unit. Do the research on whatever unit you are considering for your home, and you will be happier with your purchase.