SEER vs. SEER2 | Understanding The Difference

Heating, refrigeration, and air conditioning are responsible for a significant portion of the energy consumption of a building (be it a residential house or a commercial space). If we look at historical data, the contribution of HVAC systems towards the emission of greenhouse gasses (which are responsible for climate change and global warming) has always been a concern. Hence the need for energy-efficient and environmentally friendly HVAC systems is more pressing than ever. But how do we measure the energy efficiency of an HVAC system? The EER and SEER are two important ratings that are commonly used to determine the energy efficiency of air conditioners, heat pumps, etc. Recently, a new energy rating in the form of SEER2 has emerged. This has led to some confusion among homeowners and HVAC installers regarding which rating system to consider, SEER or SEER2.

In this guide, we will explore the fundamentals of both SEER and SEER2, examine their differences, and discuss how they impact homeowners. Whether you’re in the market for a new heating or cooling system, this SEER vs. SEER2 comparison will assist you in selecting a more energy-efficient unit.

What Is SEER? 

Seasonal Energy Efficiency Ratio or SEER is a common way to represent the efficiency of central air conditioners and central air conditioning heat pumps in the United States over a cooling season. As per AHRI (Air Conditioning, Heating, and Refrigeration Institute), SEER is the ratio of the cooling output of the unit (measured in BTU/h) during a cooling season to the total electrical energy input from the utility during the same period.

SEER = Total Seasonal Cooling Output / Total Electrical Energy Input

Simply speaking, the SEER rating determines how much energy (and thereby money) an HVAC unit requires to function over an entire year. Air conditioners or heat pumps with higher SEER ratings will consume less energy to provide the same level of cooling.

Before the adaptation of SEER, HVAC manufacturers rated their systems by measuring the energy consumption when the unit is running at maximum capacity in a controlled environment (fixed indoor and outdoor temperatures). You might’ve already heard or seen this rating system as EER or Energy Efficiency Rating. This was a very inefficient way to rate ACs and heat pumps. Things are a little bit different with SEER as it represents the performance of an AC unit in cooling mode over a range of outdoor weather conditions.

Let us assume you have an older air conditioning unit with a SEER rating of 10. If you upgrade this with a newer model that has a SEER rating of 14, you can potentially reduce the power consumption by almost 28%.

How To Calculate Energy Cost Using SEER? 

There is a simple formula to calculate the annual cost of electric energy consumed by an air conditioner.

Annual Cost of Energy ($) = Total Energy Drawn from Utility Annually (in kWh) × Average Cost of Energy (in $/kWh)

Total Energy Drawn from Utility Annually (in kWh) = Total Power Drawn from Utility (in kW) × Total Annual Operating Hours (h)

Total Power Drawn from Utility (in kW) = AC System Rating or Size (in BTU/h) ÷ SEER Rating (in BTU/Wh)

If the size of the air conditioner is given in ‘tons’, then you can convert it to BTU/h by multiplying the tons with a constant 12,000 (BTU/h)/ton.

For example, take a house in Denver with a 6-ton air conditioner that is operating 6 hours per day for a total of 150 days in a year. The SEER rating of the AC unit is 10 BTU/Wh and the average energy cost in Denver is about $0.15/kWh. We can calculate the annual energy cost of running this air conditioner as follows:

Size of the AC Unit = 6 tons × 12,000 (BTU/h)/ton = 72,000 BTU/h

Total Power Drawn from Utility = 72,000 BTU/h ÷ 10 BTU/Wh = 7,200W or 7.2kW

Total Energy Drawn from Utility Annually = 7.2kW × 6 h/days × 150 days = 6,480 kWh

Annual Cost of Energy = 6,480 kWh × 0.15$/kWh = $972

However, if you upgraded the air conditioner unit with a better SEER rating unit, say 14, then the annual cost will be only $694.

What Is SEER2? 

Up until 2023, SEER was the standard way to rate central ACs and heat pumps for their energy efficiency. But starting from January 1, 2023, these units will be tested using the new Seasonal Energy Efficiency Ratio 2 or SEER2 standards. How is SEER2 different from SEER?

SEER2 aims to provide a comprehensive, realistic, and more accurate efficiency rating by taking real-world abilities of an HVAC unit such as its cooling capacity, distribution of cooling, removal of humidity, and energy usage of the system into consideration.

We know that modern air conditioning units never stay on all the time. As soon as the room temperature reaches the temperature set on the thermostat, they go to standby mode to save power. As the room temperature changes, the unit switches back on and once again starts cooling the room. There is a small amount of energy lost when the unit switches on and off repeatedly. We call them cycling losses. SEER2 rating takes these energy losses into account while calculating the energy efficiency. Apart from this SEER2 also considers the amount of heat removed by a HVAC unit from a space in a typical annual cooling season.

Another improvement that the DOE (Department of Energy) made in SEER2 is the implementation of new test conditions that involve the M1 Blower. The new M1 test procedure in SEER2 increases the external static pressure from 0.1-inch of water in SEER to 0.5-inch of water in SEER2. This condition can accurately emulate static pressure on HVAC systems, say rainstorms during summertime.

In addition to this, SEER2 also takes into account the following parameters:

• Region/Climate Zone
• Partial load
• Varying load
• Standby mode
• Different indoor and outdoor temperatures

Impact Of SEER2 On Consumers, HVAC Manufacturers, And Dealers 

While HVAC units with SEER2 ratings are slightly more expensive than older SEER-based systems, DOE estimates that these new energy efficiency standards for split-system central ACs and heat pumps would contribute to a significant reduction in energy consumption.

This would benefit the consumers in the longer run in terms of electricity bills. Make sure to check the yellow-black ‘Energy Guide’ label on the side of the unit and look for its SEER2 rating. If you purchase an AC with SEER2 16 (and EER2 12) or above, then you will be eligible to get a tax credit of $600. Tax credit for heat pumps is region-specific. For instance, in Ohio, you need to purchase a heat pump with a minimum SEER2 15.4 and HSPF2 8.1 rating to get the tax credit. 

HVAC manufacturers must now design and produce their units that are compliant with the latest SEER2 standards. The minimum SEER2 rating requirement on average all over the United States is 14. For higher SEER2 ratings, manufacturers must employ additional tactics such as multiple compressors or thermal expansion valves.

Since January 2023, HVAC dealers and distributors have not been allowed to sell HVAC units with a SEER2 rating under 14.

SEER vs. SEER2: Ratings Range And Minimum Values 

There is no fixed range for either SEER or SEER2 ratings. You can find HVAC systems with a SEER rating of as low as 9 or as high as 42 (or even more). This applies even to the new SEER2 standard. What’s important is the minimum SEER rating (or SEER2 rating).

In 1992, the minimum SEER rating for all air conditioners (central and window) was 10. But in 2006, SEER 13 was the minimum for all central air conditioners (window ACs still had a minimum SEER rating of 10). In order to get ENERGY STAR qualification, central ACs must have at least SEER 14.5.

DOE made some changes to energy conversion rules in 2011 that came into effect in 2015 SEER rating. Instead of one minimum SEER requirement for the entire country, now we have different regions for a better representation of regional climate. The regions are:

• North (AK, CO, CT, IA, ID, IL, IN, KS, MA, ME, MI, MN, MO, MT, ND, NE, NH, NJ, NY, OH, OR, PA, RI, SD, UT, VT, WA, WI, WV, WY)
• Southeast (AL, AR, DC, DE, FL, GA, HI, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, U.S. Territories incl. Puerto Rico)
• Southwest (AZ, CA, NM, NV)

All split-type central ACs in the North regions must have a minimum of SEER 13. Coming to Southeast and Southwest regions, central ACs must be at least SEER 14. In addition to the SEER rating, central ACs in the Southwest region must also have an EER 12.2 rating.

From 2023, SEER2 replaced SEER ratings in all three regions. The following table indicates the minimum SEER2 ratings necessary for all residential split-system central air conditioners.

In the case of heat pumps, all the units must have a minimum of SEER2 13.4 rating irrespective of the region.

Benefits Of Higher SEER/SEER2 Rating 

Upgrading from a lower SEER AC to a unit with a high SEER rating will definitely put a dent in your wallet. But there are a couple of important benefits of a higher SEER2 rating.

• Energy Efficiency: The higher the SEER2 rating, the higher the energy efficiency i.e., low energy consumption for the same level of cooling. An upgrade from a 10 to 14 SEER will consume almost 28% less energy. This can hugely impact the electricity bill.
• Environmental Impact: With a higher SEER rating and less energy consumption, the carbon footprint of the HVAC system will become small.

SEER vs. SEER2: Differences 

• Cooling And Heating: SEER considers only the cooling efficiency of an HVAC unit over a cooling season. SEER2 on the other hand considers both cooling and heating efficiency over a year.
• Calculation Methods: SEER calculates energy efficiency by taking the ratio of total cooling output in a typical season and total energy consumption during the same period. SEER2 measures energy consumption over many diverse conditions though. In addition to cooling, SEER2 also takes heating energy consumption into account for the whole year to calculate efficiency.
• External Static Pressure: While measuring SEER, the external static pressure is maintained at 0.1 inches of water. This has been increased by a factor of 5 to 0.5 inches of water in SEER2 to accurately depict real-world field conditions.
• Efficiency Evaluation: Both SEER and SEER2 are efficient ways to represent energy consumption. SEER ratings usually take cooling season performance and a small set of metrics for calculation. SEER2 ratings give a broader picture over the entire year by considering cooling as well as heating.
• SEER Value: Generally speaking, SEER values are higher than SEER2 values. Several factors influence this but the inclusion of heating performance in SEER2 is the main difference (HVAC units are usually more efficient at cooling than heating).

SEER vs. SEER2: Comparison Chart 

While SEER2’s newer set of test conditions and higher overall standards would result in a more accurate measurement of real-world energy usage, it doesn’t automatically make them more efficient than SEER. It just means the process of testing the HVAC unit’s performance became much harder. That said, for the same cooling efficiency, the SEER ratings are slightly bigger than SEER2.

The following SEER vs. SEER2 comparison chart shows some of the possible SEER rating and their corresponding SEER2 ratings for central air conditionals.

NOTE: The SEER2 ratings for window air conditioners are the same as SEER ratings.

Conclusion

The rating system such as SEER and SEER2 have a major impact on the cost of the AC unit, its energy efficiency, utility bills, and the overall performance of the air conditioning system. The switch from SEER to SEER2 for measuring the energy efficiency of ACs and heat pumps is crucial as the newer technique allows for a much more accurate analysis by considering several real-world parameters.

If you are purchasing a new central AC or heat pump in 2024, then you need to check if the unit is compliant with the minimum SEER2 requirement in your region. As a reminder, a higher SEER/SEER2 rating, better energy efficiency.