What Do Those HVAC Efficiency Acronyms Mean?

What Do Those HVAC Efficiency Acronyms Mean?

Defining SEER, EER, HSPF, & AFUE

Bob, the eComfort Product Expert
Product Expert

Efficiency is important in all aspects of life because it measures how much you get out of something versus how much you put in. How much work can you get done per hour? How much money do you make per dollar spent on education?

The same principle applies to heating and cooling equipment. You want to measure how much heating or cooling your system provides per amount of fuel used. When shopping for equipment, you'll encounter different ways to measure HVAC efficiency ratings, and it can get confusing. That's why we'll go over each one below and let you know how to find more information. 


Cooling Efficiency Ratings

The two efficiency ratings you should know when it comes to cooling equipment like air conditioners and mini splits are SEER and EER.

Seasonal Energy Efficiency Ratio (SEER)

The Seasonal Energy Efficiency Ratio (SEER) is the standard measure of efficiency for air conditioning and mini split systems. The rating is a simple ratio: the total cooling output from a piece of equipment in BTU divided by the energy it consumed in watt-hours. This means that it can somewhat be thought of as an average efficiency over the cooling season.

Mini Split Condensors

One important thing to remember when checking a unit’s SEER and other efficiency ratings is that the rating is a useful benchmark for comparing products, but your climate and usage pattern will determine how efficiently the unit will operate in your home.

Most central air conditioners today have a SEER rating between 13 and 18, with those at the higher end of this range considered very energy efficient.  Mini-split systems, however, can see SEER ratings as high as 28.

Energy Efficiency Ratio (EER)

Goodman High EER Heat PumpThe closely related Energy Efficiency Ratio (EER) is found by dividing the output cooling (in BTU) by the electric energy input (in watt-hours) at a specific operating point. Unlike SEER, EER is not a seasonal measurement and is better used in stable, warm climates.


Heating Efficiency Ratings

When it comes to heating efficiency ratings, you should understand HSPF and AFUE.

Heating Seasonal Performance Factor (HSPF)
Goodman High Efficiency SystemIf you’re looking to save energy, one option for you might be a heat pump. In brief, a heat pump is an air conditioner that can work backwards – it can transfer heat from the indoors out and from outside in.

When it cools, its efficiency is measured using SEER and EER as discussed above. When heating, efficiency is measured using the Heating Seasonal Performance Factor (HSPF) rating. 

Like SEER and EER, the higher the rating, the more efficient the heat pump. It’s also a similar measurement: heat output over a typical heating season (in BTU) divided by the electricity used (in watt-hours). Be careful when comparing HSPF and SEER, because the range for HSPF is shifted a bit lower than SEER, with the most efficient systems maxing out around 12 HSPF.

Department of Energy Minimum Efficiency Requirements 

The U.S. Department of Energy (DOE) periodically updates minimum SEER, HSPF, and EER requirements. The table and map below indicate minimum ratings by equipment type and region. Note that these standards apply to new equipment being manufactured. Existing equipment below these standards is fine to use, although it's wise to know where the nation is moving on efficiency.

seer and hspf region map

System Type North Region Southeast Region Southwest Region
Split System Air Conditioners 13 SEER 14 SEER 14 SEER / 12.2 EER (<45k BTU)
14 SEER / 11.7 EER (>45k BTU)
Package Air Conditioners 14 SEER 14 SEER 14 SEER / 11.0 EER
Split System Heat Pumps 14 SEER / 8.2 HSPF 14 SEER / 8.2 HSPF 14 SEER / 8.2 HSPF
Package Heat Pumps 14 SEER / 8.0 HSPF 14 SEER / 8.0 HSPF 14 SEER / 8.0 HSPF
Package Gas/Electric Furnaces 14 SEER 14 SEER 14 SEER

Annual Fuel Utilization Efficiency (AFUE)
Weil-Mclain High AFUE Boiler
Most people in the United States use furnaces or boilers for their whole-home heating solutions. Since a different source of fuel is used for these systems, a different furnace efficiency rating is used: the Annual Fuel Utilization Efficiency (AFUE).

AFUE is expressed as a percentage, not a rating like SEER, EER, or HSPF. It measures the thermal efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace.

Today, average boilers see AFUE percentages around 80% (meaning 80% of the energy put into the unit is turned into useful heating energy), while high efficiency condensing boilers have efficiencies of 90% AFUE or greater. When choosing a furnace, besides looking at AFUE, you should also look at Low NOx emissions requirements, particularly in states like California, Texas, and Utah.

While these four ratings are very important to making a fully informed decision about your heating and cooling, there are likely other factors that you need to be aware of to ensure you make the best choice for your space. If you ever need any assistance, our highly-trained Product Advisers and engineers are happy to help – just give us a call at 866-554-HEAT (4328).

arrow NEXT: How Efficiency Ratings Can Save You Money

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Bob, the eComfort Product Expert
Product Expert
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