The Guide to Understanding SEER Ratings

Table of Contents

1. What's a SEER rating?
2. How is it calculated?
3. Does SEER matter?
4. How do you find the SEER of your system?
5. What makes a system higher SEER?
6. Higher SEER, higher comfort
7. SEER 1 vs. SEER 2
8. SEER isn't all that matters

1 What's a SEER rating?

The simple answer: how much energy (and money!) is required to operate an A/C system.

The longer answer is that it stands for Seasonal Energy Efficiency Ratio (or Rating). This rating essentially tells you how efficiently your A/C system converts electricity into cool air. 

2 How is a SEER rating calculated?

The SEER rating is calculated by dividing the total cooling output of a system over a typical cooling season by the total energy input in watt-hours during the same period. Essentially, a higher SEER rating indicates a more efficient air conditioning system.

Some FACTS about SEER ratings:

• The Air Conditioning, Heating, and Refrigeration Institute (AHRI) tests all A/C systems to determine their SEER rating.
• A/C systems generally can range from 14 SEER to 28 SEER.
• SEER is not the same as EER for FUE ratings, though they are all meant to measure energy efficiency.
• 14 SEER is the minimum for new systems for the North, and 15 is the minimum for the south.

3 Does SEER matter?

Of course it does! Replacing a 15-year-old system, for example, might save between 20 and 40% on your energy costs each year—or higher if your systems are older and you install a super high-efficiency system.

Think of it like your car's gas mileage. A fuel-efficient car goes further on a gallon of gas, just like a high-SEER A/C system keeps your home cool using less energy. So, in the same way that you’d want to know how many miles per gallon your new car will get, it’s important to understand the SEER rating of your new A/C system. Higher SEER systems also have key benefits that go far beyond energy efficiency, which we will explain later in this article.

4 How do you find your system's SEER rating?

There are a few ways:

1. Check the yellow EnergyGuide sticker on your outdoor condensing unit.
2. Look up the model number. A model number like "RA16" usually indicates a SEER rating up to 16. (Visit ahrinet.org and search for your model number to find the official rating certificate.)
3. Contact your HVAC technician or service provider for assistance.

For split systems, it’s important to remember that the combination of the inside air handler and the outside condensing unit determines the SEER rating. A condenser might be up to 20 SEER for example, but if the air handler is not as efficient, the overall SEER rating will be lower.

5 What makes a high SEER system?

Several factors contribute to a higher SEER rating in air conditioning systems:

• Better Technology. Higher efficiency systems have more technology packed into them that allows the A/C to use less energy.
• The Size. Larger components, especially A/C coils, result in higher SEER ratings. That’s why a new unit is almost always physically larger than a unit that is 20 years old.
• Enhanced Heat Exchangers: Larger or more effective heat exchangers improve heat transfer, making the system more efficient.
• Improved Refrigerants: Newer, environmentally-friendly refrigerants can enhance system efficiency.
• Smart Controls: Advanced thermostats and control systems can optimize performance and reduce energy usage.
• Advanced Compressor Technology: Variable-speed compressors can adjust their output to match the cooling demand, increasing efficiency.

Note: The key technology difference between lower and higher SEER systems is the compressor. To simplify things a little bit, we can think about 3 main groupings of compressors:

• Single Stage: These are 14-16 SEER units. These A/C systems operate like a normal light switch. They are on at 100% or off at 0%.
• Two Stage: These are 16-17 SEER units. These A/C systems operate like the headlights on your car. There are high beams, regular lights, and off.
• Variable Speed: These are 18 and up to 28 SEER units. These A/C systems operate like lights on a dimmer. You can control the price level of output.

The more stages a compressor has, the less it has to “overwork.” If it’s warm but not hot, it can run in a lower setting, which saves energy.

Two-stage and especially variable-speed compressors also require many additional sensors and a control board so they know precisely how hard to work. When you open up a variable-speed A/C, you’ll think you’re looking at a computer—and in a lot of ways, you are!

6  Higher SEER, higher comfort

No! While SEER stands for "Energy Efficiency", it’s important to understand that's not the only advantage, including greater home comfort.

Key advantages of higher SEER units:

• Greater humidity control. Because higher SEER systems have advanced controls and sensors, they can do a much better job maintaining ideal humidity conditions.
• More even indoor temperatures. The on-cycle vs. off-cycle of a single-stage system can leave some rooms warmer than others. The continuous operation of a variable-speed system however, allows the temperature to be much more even.
• Less fluctuation in indoor temperature. Because higher SEER systems have more “stages,” they can keep the temperature in your house at much more precise levels. So, if you like 72 degrees, a variable-speed system will always be right around 72 vs. a single-speed system, which might fluctuate a few degrees around 72.
• Silence is golden. Higher SEER systems tend to be quieter because they are smoother and more continuous in their operation. This is a big advantage for home comfort.
• Cost Savings: Lower energy consumption translates to reduced utility bills over time.
• Environmental Impact: Efficient systems reduce greenhouse gas emissions and reliance on non-renewable energy sources.

7 SEER1 vs. SEER2

In 2023, the Department of Energy (DOE) moved from the original SEER rating system to the new SEER2 rating system.

The old and new SEER ratings are similar, but they are not exactly the same. The new SEER2 system is meant to capture better “real world” conditions vs. factory conditions. The tests are still done in a factory, but they are now done under conditions of higher static pressure. 

In other words, systems rated under SEER 2 standards provide a more precise indication of expected performance and efficiency.

For example, a unit that is 14 SEER2 rated is in general a bit more efficient than a 14 SEER1 rated unit.

8 SEER isn’t all that matters

While the SEER rating of the system is critical for energy efficiency and home comfort, it’s important not to forget about

• Ductwork: Don’t lose cold, crisp air to leaky ducts! Even a top-of-the-line system will waste significant money on your energy bill if it loses air to leaky or poorly designed ducts.
• Insulation: You want to keep the colder, conditioned air where it belongs—in your living area. With nearly 90% of homes under-insulated, your A/C system is probably working much harder and longer than it needs to.
• Thermostat: A smart or programmable thermostat is one of the cheapest and simplest energy-saving additions you can make to your home. There is no reason to keep the temperature at 72 degrees when no one is home to enjoy it!

In conclusion, understanding SEER ratings is vital for making informed decisions about your air conditioning system. While higher SEER ratings offer numerous benefits, it's essential to consider all factors to ensure you choose the best system for your needs.