Purchase the Perfect Air Conditioning Unit By Understanding The SEER Rating

The terms retailers and manufacturers use when describing air condition systems can seem foreign to the everyday buyer, making purchasing a new air conditioner a daunting task. One common term, the Seasonal Energy Efficiency Ratio, or SEER, rating, is important to understand before you make a purchase.

Electricity Power MeterThe SEER rating tells you how efficient your system will be. The higher the rating, the less electricity your system will need to cool your house. The rating is derived from the ratio of cooling output to electrical energy used by your system over a cooling season.

When looking at SEER ratings, be aware that a cooling season has varying temperatures from 60 to 100 degrees, and the SEER rating reflects the overall seasonal efficiency of your air conditioner, not the everyday efficiency of your system.

It might make things more clear to think of a SEER rating like the miles per gallon of a car. Though a car can run at 20 MPG, the true MPGs the car gets depends on road conditions and traffic. Just like that, a SEER rating can fluctuate day-to-day depending on how your unit is running.

Deciding what SEER rating is right for you

Once you know what a SEER rating is, it’s time to look at your home.

Take stock of how often you run your air conditioner and at what temperature. If the desired temperature in your home is often set several degrees below the outside temperature, or if you live in an older, draftier home, springing for a higher SEER rating may be ideal for you.

In the Southeastern United States where temperatures are elevated for a larger portion of the year, a higher SEER rating is recommended. Starting in 2015, ducted air conditioning units and smaller, mini-split systems installed in this area have a required SEER rating of at least 14.

So, how high is high enough? If you want to go by cost alone, you might need to do some math.

Online and in store, you may have noticed the “3-ton” or “5-ton” label on each unit. This number is not a weight description, but shorthand for Refrigeration Ton, the amount of energy it takes to melt one ton of ice.

Your bill measures your electricity use in a unit called kilowatt-hours, which comes from a different measure of energy called the British Thermal Unit (Btu). One Btu is enough energy to raise the temperature of a pound of water by one degree Fahrenheit. There are 12,000 Btu’s per hour in one Refrigeration Ton.

It can seem complicated but stick with me, this is where the math comes in. Let’s say you have an older 3 Ton 12 SEER unit (bellow the currently required SEER rating).

First, we must convert to the proper units:
3 Tons X 12,000 Btu = 36,000 Btu/h

Next, we use the SEER value:
36,000 Btu / 12 SEER = 3,000 Wh (watt-hours)

Now we must convert watt-hours to kilowatt-hours, the unit your provider uses.
3,000 Wh/1000 = 3 kWh consumed every hour of operation

We will say you run your unit about 2,500 hours annually.
2,500 hours x 3 = 7,500 kWh consumed yearly

Time to calculate your yearly cost of operation.
7,500 kWh x 10 cents per kWh = $750

You will need to substitute your own hours of operation and the rate you pay per kWh, but using this equation will allow you to see the difference in savings for each SEER rating.

Moving BoxesYou’re not done yet, though.

It’s time to think about how long you’ll be living in your current home. Air conditioning units are expensive, and you can’t take them with you when you move. A higher efficiency machine won’t bring a return on your investment in one cooling season, so you must consider how many seasons of use you will get out of your system. Using the calculations above, think about your savings per year and the cost difference between each efficiency rating. This will tell you how long it will be before your system pays for itself.

If you set time aside to do these calculations and think about the condition of your home, you will become a more informed buyer and will be able to decide what SEER rating is right for you.