How Much Do You Need To Know About SEER Ratings?
SEER stands for seasonal energy efficiency ratio. This value is one of the first things you'll see when browsing split-unit central air conditioning systems. It replaces the simpler EER (energy efficiency ratio) found on window units or portable air conditioners. While it's reasonably easy to compare the SEER of two units, it can be helpful to understand a little bit more about this important specification.
What Makes SEER Special?
SEER provides a more accurate measure of an air conditioning system's efficiency than the metrics used on more basic air conditioners. The more straightforward EER rating is a direct ratio of the system's capacity divided by power usage. This value allows you to compare air conditioners, but assumes a fixed temperature and constant usage throughout the cooling season.
The "S" in SEER adds an additional component. Since air conditioners typically don't run at full power throughout the cooling season, the SEER rating combines several EER ratings, each at a different expected power load. The SEER designers weighted these individual EER components based on expected operating time under varying loads throughout the season.
It's not necessary to know how to calculate your SEER rating, but it's important to understand how it differs from other efficiency measures. Since air conditioners may be more (or less) efficient when operating under partial load, SEER provides a clearer picture of your actual operating costs throughout the summer.
How Can You Use SEER Ratings?
Since SEER is still a combination of simple ratios, the good news is that there's a linear relationship between different SEER ratings. In other words, an air conditioner with a SEER rating of 20 will be about twice as efficient as an air conditioner with a SEER rating of 10. Theoretically, you can trivially compare your current system to a new one by looking at the SEER ratings.
In practice, SEER ratings can sometimes be deceiving. These values provide a theoretical way to compare two systems, but efficiency can vary based on your use cases. For example, if you keep your thermostat setpoint unusually low, you may not be able to achieve the full efficiency of your new system. Leaky ductwork or other problems can cause your system to operate less efficiently.
In general, SEER ratings provide an excellent starting point to compare systems you're considering, but you shouldn't rely on them to make your decision. Instead, discuss your needs and expectations with a qualified installer. An air conditioning service can help you decide which system will fit your needs and may be able to recommend special features, such as variable-speed compressors, to meet your cooling requirements.