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Curious about how to determine how efficient a cooling or heating system is? Use these acronyms to help you find the right product for your home, business, or other building type.

HVAC Efficiency Acronyms

Defining SEER, EER, HSPF, & AFUE

Product Expert
HVAC Efficiency Acronyms

Efficiency ratings are essential when looking for a new heating or cooling system.

Efficiency not only impacts your annual energy budget, but also carries an environmental impact as well. In the heating and cooling industry, there are four main ratings used to express energy efficiency: SEER, EER, HSPF, and AFUE.

While all four provide some measure of insight into a systemís efficiency, they are not all used for the same types of products, and some may be more important than others when making a purchasing decisions. Not to worry, we are here to help you decode these industry ratings as they relate to you.



Mitsubishi High SEER System
Seasonal Energy Efficiency Ratio (SEER)
The Seasonal Energy Efficiency Ratio (SEER) is the standard measure of efficiency for air conditioning 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.

One important thing to remember when checking a unitís 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 Pump

The 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.† While the SEER rating will tell you how your unit will likely perform over the course of a summer, the EER is used to compare units while keeping conditions constant.† Because of the conditions typically used during testing of EER, EER often reflects efficiency at peak (although not necessarily extreme) use and, thus, is lower than SEER.


Heating Seasonal Performance Factor (HSPF)
Goodman High Efficiency System

If youíre 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 Ė 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.† Itís 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.

Annual Fuel Utilization Efficiency (AFUE)
Weil-Mclain High AFUE Boiler

Most people in the United States, however, use furnaces or boilers for their whole-home heating solutions.† Since a different source of fuel is used for these systems, a different 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.

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 Ė just give us a call at 866-554-HEAT (4328).

NEXT: How Efficiency Ratings Can Save You Money

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