If you’re in the process of looking for a new central AC for your Las Vegas, NV, home, you’ve probably encountered something called SEER ratings. Although you may understand that a SEER rating is a relative measurement of how efficient an AC is, you may not know exactly how manufacturers arrive at the ratings. That makes it difficult to judge the real-world efficiency differences you can expect from two AC options. It also makes it hard to determine if the difference in price between two AC units with different SEER ratings is worth paying. To help, here is a complete explanation of the SEER rating system. We’ll cover what SEER ratings mean, how they’re calculated, and the right way to use them as a factor in your AC purchase decision.

What Is a SEER Rating?

SEER is an acronym that stands for Seasonal Energy Efficiency Ratio. It is a measure of an AC system’s efficiency that attempts to simulate how the unit would perform during an average cooling season. SEER ratings exist to provide buyers with a simple, number-based system to compare the efficiency of different AC models. The higher the SEER rating an AC achieves, the more efficient it is. The SEER system is also the basis for federally mandated efficiency minimums in different regions of the US. Here in Las Vegas, you cannot legally purchase a central AC system with a SEER rating any lower than 15.

The SEER rating system dates back to 1978 as a part of the National Energy Policy and Conservation Act (NEPCA). The law empowered the Department of Energy (DOE) to create the SEER system so it could devise and enforce the aforementioned minimum efficiency standards. However, as a result of bureaucratic infighting, the initial minimum SEER standards for air conditioners didn’t go into effect until the early 1990s. From that time on, all HVAC companies could only legally sell systems that complied with the minimum SEER standard at any given time.

As of January 2023, the DOE revised the SEER system’s testing methodology so it would better reflect the real-world use of AC systems. As a result, the SEER ratings you see on AC systems today are actually following a standard called SEER2. However, the number scores still work the same as they always did, with higher scores meaning you’re looking at a more efficient air conditioner.

The Formula for SEER Ratings

To arrive at a SEER rating for a given air conditioner, its manufacturer puts it through a series of tests using very specific testing conditions. The conditions attempt to simulate the installation conditions of the unit as they’d exist in the average home. Calculating the SEER rating begins by finding a more basic measure of efficiency known as the energy efficiency ratio (EER). EER is the result of dividing an AC system’s hourly BTU output by its maximum wattage. EER lets you know how much energy an AC uses in an hour while running at maximum output in simulated real-world conditions.

However, an AC would never be used continuously at maximum output in the real world. That’s where the SEER rating comes in. It uses the EER of an AC system and plugs it into a mathematical formula that estimates how the AC would be used during an average cooling season. The SEER formula assumes that you’d use an AC:

At 100% output for 1% of the cooling season

At 75% output for 42% of the cooling season

At 50% output for 45% of the cooling season

At 25% output for 12% of the cooling season

The SEER rating’s testing conditions also assume that you’d be using the AC in summer conditions that average between 82 and 83 degrees Fahrenheit. That is important to know, given that we see average summer high temperatures in the triple digits here in Las Vegas. That means the SEER rating you see on an air conditioner isn’t reflective of how the system will perform here. It is also why the minimum SEER rating standard is higher in the south and southwest than it is in the northeast.

How Much Difference Does 1 SEER Make?

The good news is that you can still use SEER ratings to judge the relative efficiency of one AC versus another. However, in doing so, you must take into account that efficiency gains on the SEER scale aren’t linear. The higher the SEER number the less of a gap there is between it and a system with a SEER rating one digit lower.

For example, the efficiency difference between an AC system with a 15 SEER and one with a 16 SEER is around 6.67%. However, the efficiency difference between an AC system with a 22 SEER and one with a 23 SEER rating is just 4.54%. That means the efficiency gains diminish as you move up the scale. That can and should play a role in how you evaluate the price differences between AC systems with different SEER ratings.

Even better, you can use a quick mathematical formula to find the efficiency difference between two AC systems, no matter how far apart their SEER ratings are. To do it, simply divide the higher SEER rating by the lower SEER rating, subtract one, and multiply the result by 100%. So, if you were comparing an AC with a 20 SEER with one that has a 15 SEER, plugging those numbers into the formula would tell you that there’s a 33.3% efficiency difference between the two. You could then use that information along with your home’s electricity costs to determine approximately how long the more expensive and efficient AC would take to pay for itself compared to the cheaper and less efficient one. You could also use the formula to compare your home’s current AC system’s efficiency to any prospective replacement. That might help you justify the cost of a new system even if your existing one is still working.

Your Local Air Conditioning Experts

Now you know everything there is to know about SEER ratings, including how to use them as you consider an air conditioner purchase. Or you can just consult with the experts here at Simply Air Conditioning Heating & Plumbing, who can do all the math for you and help you pick the perfect AC for your needs and budget. For over 6 years, we’ve offered the finest quality HVAC services to homeowners in and around Las Vegas. Whether you need an HVAC installation, repair, or regular maintenance, you can entrust the job to our team of experienced HVAC technicians.

Plus, we offer ductwork, indoor air quality, and plumbing services, too. We even offer financing options on approved credit to make it easier for you to afford the new HVAC system your home needs. So, when you’re ready to purchase a new AC for your Las Vegas home, call the team at Simply Air Conditioning Heating & Plumbing right away!