June 10, 2024
The Meaning Behind HVAC Efficiency Ratings

HVAC efficiency ratings are an invaluable tool for homeowners purchasing a new system. This information informs you how environmentally friendly a system is and how much it will cost to run over its lifespan. Use that information to compare any system to another and make a better buying decision. With this in mind, let’s explore the different rating systems you may encounter.


The British thermal unit (BTU) is a measure of energy and heat in particular. While it isn’t a measure of energy efficiency, it’s an important concept in the HVAC space. Many of the energy efficiency ratings we’ll discuss here use BTUs in their equations or as a criterion.

One BTU represents the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. A BTU is equal to about 1,055 joules. As a general rule when sizing an air conditioner, you need 20 BTUs per square foot. Most central ACs and mini-split systems in the U.S. are 45,000 BTU units. Most furnaces are within the 80,000 to 100,000 BTU range.


The seasonal energy efficiency ratio (SEER) measures cooling efficiency over an entire theoretical cooling season. Manufacturers test their ACs and heat pumps in a laboratory setting. They then divide the BTUs of heat removed from the air by the total energy in watt-hours required.

What the consumer should know is that the higher the SEER, the cheaper the AC or heat pump is to run. It’s also important to know that the Department of Energy (DOE) sets minimums on a regional basis. There are three regions in the U.S. for the purposes of energy efficiency ratings: North, South and Southeast. As of 2023, the minimum SEER is 14 in the North, and 15 in the South and Southeast.

There are systems with SEER ratings well above the minimums. When the new minimums went into effect in 2023, there were central ACs with SEER ratings in the 20s. There were also mini-splits with SEER ratings in the 30s. Whether a higher SEER is worthwhile is a matter of comparing the added initial cost to the long-term savings.

SEER 10 was the minimum when the DOE introduced the concept of energy efficiency minimums in 1992. If you currently have a SEER 10 AC and upgrade to a SEER 14 AC, you would reduce your electricity consumption by 28%.


Heating seasonal performance factor (HSPF) is similar conceptually to SEER. The fundamental difference is that it measures heating efficiency rather than cooling efficiency. HSPF is relevant specifically to heat pumps. Heat pumps are similar to ACs but have a reversing valve that lets them provide heating too. Furnaces generate heat directly. Heat pumps transfer heat energy.

The minimum HSPF set by the DOE as of 2023 is 8.8, which is quite a bit less than the minimum SEER. Current air-source heat pump technologies are less efficient heating than they are cooling. This is because they use heat energy in the ambient air. In the summer, heat energy is abundant. In the winter, it’s not. Ground-source or geothermal heat pumps offer HSPF ratings comparable to their SEER ratings. This is because the earth is abundant with heat energy even in the winter.


In 2023, the DOE introduced SEER2 and HSPF2 as new versions of the SEER and HSPF rating systems. The main difference is that they now factor in the static air pressure of the air handler. This provides consumers a more accurate energy efficiency rating for ducted systems, such as central ACs. The minimum SEER2 is 13.4 in the North and 14.3 elsewhere. The minimum HSPF2 is 7.5.

Starting in 2023, all new ACs and heat pumps must have a SEER2 and HSPF2 rating available to consumers. This is in addition to the required SEER and HSPF ratings. Note that you cannot compare SEER to SEER2 and HSPF to HSPF2. At a currently undetermined time in the future, the DOE will deprecate the old rating system.


Annual fuel utilization efficiency (AFUE) measures the energy consumption efficiency of furnaces and boilers. An 80 AFUE furnace converts 80% of the fuel it burns into heat. It wastes the other 20% as a byproduct. The minimum AFUE as of 2023 for all three regions is 81. You also have the option of a high-efficiency furnace or boiler. These are also known as condensing furnaces and boilers. They reclaim heat energy from their exhaust. This allows for an AFUE of at least 90% and as high as 98.5%.

Electric furnaces have an AFUE of 100%, but this is a bit misleading. It’s true that they’re more efficient in that they lose no energy in the production of heat. That said, it’s an apples to oranges comparison. Electric furnaces are much more expensive to run.


Energy efficiency ratio (EER) measures cooling efficiency. The difference between EER and SEER is that EER measures peak efficiency at 95 degrees Fahrenheit. SEER is much more informative to the average consumer choosing a central AC or heat pump. It just doesn’t stay hot enough long enough in the U.S. for EER to be relevant to consumers. That isn’t the case when it comes to window ACs and other room-based ACs. In those cases, EER is a good measure of your long-term costs.

The DOE introduced combined energy efficiency ratio (CEER) in 2014. It measures the cooling efficiency of window and other room-based ACs. The difference between CEER and EER is that CEER also accounts for the efficiency of the unit in standby mode. That means that CEER is more valuable to the average consumer than EER.


Coefficient of performance (COP) is measure of cooling and heating performance. It applies to ACs and heat pumps. The higher the COP, the better the efficiency and the lower the cooling costs. COP is similar to EER. Seasonal coefficient of performance (SCOP) is similar to SEER and HSPF. It accounts for efficiency over a season rather than at a peak. These ratings are not commonly used in the U.S. The DOE does maintain COP and SCOP data because many other countries do use them.


ENERGY STAR is a program run by the DOE and Environmental Protection Agency (EPA). The EPA awards ENERGY STAR certification to appliances that meet certain energy consumption criteria. If a heating or cooling system has the ENERGY STAR label, you know that it’s a high performer in this regard. It can also make you eligible for federal tax credits and rebates and local and private rebates.

Your Local HVAC Experts in Maryland

If you’d like to learn more about HVAC efficiency ratings, Beltway Air Conditioning & Heating in Hanover is here to help. Our HVAC technicians install, maintain and repair all types of heating and cooling systems. That includes gas and electric furnaces, central air conditioners, heat pumps and ductless mini-splits. We also specialize in thermostats, air purifiers, humidifiers, carbon monoxide detectors and ductwork, including duct cleaning.

Our company has a plumbing team as well. We install and service well systems, sump pumps, tank and tankless water heaters and water filtration and conditioning systems. Call us today or contact us online to schedule an appointment or with any questions about these services.

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