What Do HVAC Energy Efficiency Ratings Mean?

When you're in the process of buying a new air conditioner, heat pump or heating system, you'll see numerous energy efficiency ratings listed on the units. These play a vital role in determining how much the system costs to purchase and operate. 

In general, system performance is measured by a higher seasonal energy efficiency ratio (SEER) and energy efficiency ratio (EER). Higher ratings mean lower operating costs, but they also mean higher price tags.

If you're in the market for a new air conditioner, it's worth investigating higher-rated systems. Similarly, a higher rated Heating Seasonal Performance Factor (HSPF) means a more efficient air-source heat pump.

What does SEER mean?

SEER shows the electrical input required to run the A/C over one average cooling season, compared to how much cooling the system generates. This rating is assigned based on an average, lower temperature of 82 degrees. You should know that a 16-SEER A/C achieves this rating within this temperature range but not at higher temperatures. 

What does EER stand for?

EER, on the other hand, is more like calculating the "highway miles" of the system, as it's tested based on higher operating temperatures, generally 95 degrees or higher. This rating also takes into account humidity removal, and it's useful because it shows how an air conditioner performs under maximum cooling load.

Knowing how to navigate both efficiency designations is helpful during the buying process because many homeowners need to install an A/C that functions efficiently in both conditions: mild, warm days, and hot, humid days.

You shouldn't sacrifice one rating for the other, and it's important to keep in mind that an A/C with a high SEER rating won't necessarily also have a high EER rating. Look at both ratings to make a wise purchase.

What does HSPF mean?

The heating seasonal performance factor, like SEER, measures efficiency over the course of one entire season as a ratio of heat generated to electricity consumed.

In the United States, split-system heat pumps manufactured in 2015 or later must have an HSPF of at least 8.2, and single package units must have an HSPF of at least 8. The maximum possible HSPF for today's most efficient heat pumps is 10. 

What's more important: SEER or EER?

EER measures a snapshot of a moment in time, whereas SEER measures usage over time. Therefore, HVAC experts say SEER represents a more important number to pay attention to for long-term energy usage. “I concentrate more on SEER than EER,” says Kurt Wakefield, general manager for Service Now Heating & Cooling in Clackamas, Oregon.

Josh Copeland, project manager for Air Solutions in Sand Springs, Kansas, reminds homeowners that energy efficiency rating is only one element of how much power your system will consume, and many other factors influence your energy bills during a hot summer or cold winter.

“If it’s not installed correctly, or if you’ve got duct leakage or bad insulation, the SEER and EER don’t matter,” he says. “I’ve seen cases where I put in a 14-SEER system for someone and saved them just as much money as a 20-SEER by making some upgrades to their home so they’re not losing cool air.”

Government minimums

It's helpful to learn the federal government's standards for cooling system efficiency when comparison shopping. In order to encourage energy efficiency and conservation of natural resources, the government established federal minimums for air conditioning efficiency in 1992.

Prior to 2006, manufacturers had to create air conditioners that met the 10 SEER minimum. Starting in 2006, the minimum rating was raised to 13 SEER, and as of 2015 the minimum was raised to 14 SEER for most systems except split-system air conditioners, which remains 13 across the U.S except for a few states where the minimum was bumped to 14. 

Today's cooling systems generally achieve a minimum EER 10 rating, though some states, as detailed below, have higher requirements. In order to attain Energy Star status, air-source heat pumps and central air conditioners must maintain 12 EER for split systems and 11 for package units. 

Choosing a cooling system that merely meets the minimum won't help you achieve optimal energy efficiency, however. Instead, give high-efficiency air conditioning a second look, especially if you live in a very warm or humid climate. High-efficiency air conditioners generally start at 16 SEER and 13 EER.

The meeting point

Comparing two systems with a 14 SEER rating and differing EER ratings is helpful to homeowners when comparison shopping.

A system rated 14 SEER and 10.52 EER has a lower cooling capacity at 36,000 British thermal units (BTUs), but has an increased power requirement of 3,420 watts. A 14 SEER conditioner with a higher EER of 11.37 has an increased cooling capacity (37,800 BTUs), but a lower power requirement (3,320 watts). The higher EER-rated system, therefore, costs less to operate.

No matter what ratings you choose for your new system, you can take steps around the home to drive its efficiency even higher. Talk to your HVAC contractor about sealing air leaks and upgrading insulation, and be sure to have the ductwork sized when installing new equipment.

Proper installation and care for the system goes a long way toward helping it operate at peak efficiency for many years.

How do SEER and EER affect cost?

Conventional ducted systems can reach up to 21 SEER, according to Daniel Armstrong, owner of Armstrong Mechanical Services in Hopewell, Virginia. Ductless and geothermal systems, which operate more efficiently, can reach into the 30s.

He says SEER costs vary from contractor to contractor and by region, but in his experience, a jump from 14 to 15 SEER in otherwise comparable systems costs about $1,000 extra, 14 to 17 costs about $1,800, and a 21 SEER system will probably cost about 40 percent more than a 14 SEER.

“You’ll need to find a point that meets your wallet limits and expectations,” he says. “There’s a direct correlation between how much you’re willing to spend upfront and the SEER rating.”

The Department of Energy offers online energy efficiency calculators to help homeowners predict how much money they’ll save on energy costs with equipment carrying different SEER ratings. 

Regional differences

For a variety of reasons, including climate, federal goverment rules treat some states differently for split-system SEER rules.

Starting in 2015, split-system A/C units installed in Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia or the District of Columbia must have a SEER of at least 14.

Split-system A/C units installed in 2015 or later in Arizona, California, Nevada or New Mexico must have a SEER of at least 14 and an EER of at least 11 (for package systems), 11.7 (for split-system units rated at 45,000 BTU/hour or greater) or 12.2 (for split-system units rated less than 45,000 BTU/hour.)

Do you have an HVAC or A/C system with a high energy efficiency rating? Tell us how it's worked out for you in the comments below.

Editor's note: This is an updated version of an article that was originally posted on June 18, 2013.