If you’ve ever gone shopping for a new central AC, you’ve no doubt seen the large yellow EnergyGuide sticker affixed to each model. On the sticker, you’ll find the efficiency rating of the system, expressed on a scale called SEER. The sticker intends to help you make informed purchase decisions by giving you a way to compare the efficiency of multiple ACs.
Unfortunately, it doesn’t provide instructions on how to do that or explain what the SEER rating indicates. To help, here’s some information about SEER ratings and how to use them, courtesy of our air conditioning services experts.
What Are SEER Ratings?
SEER is an acronym that stands for Seasonal Energy Efficiency Ratio. As the name suggests, it’s an efficiency scale that’s supposed to represent relative AC efficiency during an average cooling season. At a basic level, you can take SEER ratings at face value. The higher the rating assigned to a given AC, the more efficient it is.
The SEER system originated from a collaboration between the Department of Energy and the American Society of Heating, Refrigeration, and Air-Conditioning Engineers. Its initial purpose was to enable federal regulators to set minimum AC efficiency standards in the US. The first statutory minimum SEER rating went into effect in 1992. It mandated that all new ACs installed in the US must have a SEER of 10 or higher. Today, the minimum allowable SEER rating is 15.
How Manufacturers Determine SEER Ratings
SEER ratings are a product of a somewhat complex mathematical formula. However, the numbers that manufacturers plug into that formula result from data collected during standardized tests. To test a given AC model, its manufacturer sets it up in a laboratory setting under predetermined operating conditions. The environment housing the AC’s indoor unit remains at 80°F and 50% relative humidity throughout the test.
It also contains an electric heater capable of the same BTU output as the AC undergoing testing. The environment housing the AC’s outdoor unit remains at 82°F and 39% relative humidity and also has a BTU-matched heater. To gather the necessary data, the AC must run under those conditions, completing between two and four cycles of approximately one hour each.
At the end of the AC’s test run, the tester records the amount of electricity the unit used during each hour of operation. Dividing the AC’s BTU output by the number of watts it consumed in an hour yields an Energy Efficiency Ratio (EER). Finally, the tester averages the EERs recorded for each hour of testing. The average EER is the number necessary to calculate a SEER rating.
The SEER formula itself is a complex one, as it attempts to simulate how you’d use an AC in the real world. For example, your AC would rarely run at full output for an hour at a time, let alone longer. The formula compensates for that by assigning a Partial Load Factor (PLF) to different percentages of the cooling season. A PLF roughly describes the percentage of each hour during which the AC will run. The formula assumes the AC will operate at the following PLFs:
- 100% PLF for 1% of the cooling season
- 75% PLF for 42% of the cooling season
- 50% PLF for 45% of the cooling season
- 25% PLF for 12% of the cooling season
If you plug an AC’s average EER into the SEER formula, it will tell you two things: the AC’s total seasonal BTU output and its total energy consumption. If you divide the former by the latter, you get a SEER rating.
How To Use SEER Ratings in Your Purchase Decisions
If you want to factor SEER ratings into your AC purchase decisions, you’ll need to know more than the SEER scoring procedure. One thing to note is that the simulated SEER cooling season doesn’t accurately represent reality in Desert Hot Springs, CA. For one thing, we experience plenty of triple-digit days. So, an AC here will likely run at full output for more than 1% of the cooling season. That makes having a higher SEER AC far more valuable here than it would be in milder climates.
Another thing to note is that the SEER rating scale isn’t linear. That means you’ll see diminishing efficiency gains as you move up the scale. As a result, it’s hard to make apples-to-apples comparisons between two differently-rated ACs. That can make deciding if a given AC’s price premium is worth paying. The good news is that there’s a simple trick you can use to simplify a side-by-side comparison.
If you’re comparing two ACs with identical BTU outputs, you can calculate the efficiency difference between them. To do so, divide the higher SEER rating by the lower one, and subtract one from the result. Then, multiply the remaining decimal by 100 to convert it into a percentage. That percentage is the approximate difference in efficiency between the two ACs.
What’s a Good SEER Rating in Desert Hot Springs?
Even knowing everything there is to know about the SEER system won’t tell you precisely what AC to purchase. The decision typically comes down to your budget. In general, the best rule of thumb is to buy the most efficient AC you can reasonably afford. There are multiple reasons for that.
One reason is that it will reduce your home’s cooling costs for the life of your new AC. The other is that every AC loses efficiency as it ages. If you have yearly AC tune-ups, your AC will still lose at least 1% of its original efficiency each year. If you neglect your AC, it can lose up to 5% of its efficiency each year. Starting with a more efficient AC makes those losses less impactful as your system ages.
If energy savings is your primary deciding factor, you’ll need to consider more than just SEER ratings. You should also look for an AC replacement that’s capable of two-stage or variable-speed operation. Those can scale back their cooling output as conditions allow. That will help you save far more energy on milder days compared to an AC that cycles on and off at full power.
Plus, you can combine a variable-speed AC with a zoning system for even more savings. That would allow you to avoid overcooling parts of your home that you’re not in. That’s an excellent way to contain cooling costs at the peak of our summer heat.
Local Energy Efficient AC Experts
If you’re looking for a new AC for your Desert Hot Springs home, count on Hermetic Heating & Air to provide it. We sell and install ACs at multiple price points and efficiency levels. Our expert HVAC technicians can help you determine your home’s needs and aid your decision-making process.
We also offer financing options on approved credit to help you afford a new AC. That can give you the financial flexibility to choose the most efficient solution available. For efficient AC installations in Desert Hot Springs, contact our team at Hermetic Heating & Air today!
