Air conditioners are measured in a variety of ways. There’s horsepower, BTU, amps and wattage, among other information on the sticker. When it comes to efficiency however, AC units are measured by two universal standards: EER and SEER.
What are they, and how do they factor when shopping for an air conditioner unit?
What is an EER Rating?
EER stands for Energy Efficiency Ratio, which is an objective measurement of the AC unit’s efficiency. This is determined by three parameters during testing:
- A set outdoor temperature of 95° F
- A set indoor temperature of 80°
- A relative humidity level of 50%,
Based on these parameters, the EER is calculated by dividing the unit’s BTU rating with the wattage. So a 12,000 BTU AC unit that consumes 1,000 watts based on those conditions will have an EER of 12.
Units with an EER rating of 11 and above are considered to be efficient. The higher the EER rating is, the more efficient the AC unit is.
More information about EER ratings can be found in our previous blog post.
What is a SEER Rating?
SEER stands for Seasonal Energy Efficiency Ratio. Like EER, it is a measurement of an AC unit’s efficiency. However, as its name suggests, the SEER measures the unit’s efficiency over the course of an entire cooling season.
This is done by measuring the average EER over a range of indoor and outdoor temperatures, and across varying humidity levels, to simulate the run of an entire season. The higher the SEER rating, the more efficient the unit is.
EER vs SEER: What’s the Difference?
Put simply, EER measures the AC unit’s efficiency at peak cooling operation, representing the hottest time of the year. In contrast, SEER presents a more rounded measurement by determining the efficiency across the whole cooling season, through a fluctuating range of temperatures and humidity levels.
In general, EER ratings are used for smaller room air conditioners like window and through-the-wall models. Larger cooling units like mini splits and central air systems use SEER, which provides a more accurate assessment of their efficiency.
In addition, unlike EER, there is a minimum SEER rating for residential air conditioners and heat pumps sold in the US.
What is the Minimum SEER for my Location?
The Energy Independence and Security Act of 2007 regulates standard SEER efficiencies, based on the following:
- Northern states: Minimum 13 SEER
- Southern and southeastern states: Minimum 14 SEER
- Southwestern states: Minimum 14 SEER
However new SEER standards are set to take effect next year.
What are the New SEER Standards for 2023?
On January 1, 2023, the federal minimum will increase by 1 SEER for all regions, for both AC units and heat pumps:
|Region||AC Minimum SEER now||AC Minimum SEER by 2023||Heat Pump Min. SEER now||Heat Pump Min. SEER by 2023|
|South + Southeast||14||15||14||15|
The new standard will be known as SEER2. Apart from AC units and heat pumps, higher ratings will apply to:
- Single Packaged Units
- Evaporator Coils
- Gas Furnaces
The higher minimums are driven by a new testing standard from the Department of Energy, which takes into account new external static pressure conditions that better reflect real-world conditions.
According to the DOE, the current SEER testing method doesn’t accurately simulate the effect of ductwork and external static pressure on HVAC systems, so it’s less representative of real-world operating conditions.
What Does SEER2 Mean for Homeowners?
The new standards apply to residential AC units and heat pumps manufactured after December 31, 2022, so existing appliances aren’t covered. However, consumers and contractors looking to install a new air conditioner, heat pump, or any of the appliances mentioned above next year will have to abide by the new minimum SEER2 ratings.
For contractors, there is one important difference to note between regions:
- Northern states: compliance is determined by manufacturing date
- Southern states: compliance is determined by installation date
Northern contractors therefore get more leeway, allowing them to use older SEER standards as long as the appliance was manufactured before Jan 1, 2023. This also allows sell-through of older SEER inventory.
For more information about AC efficiency, check out our guide to the most energy-efficient AC units.