For those outside the HVAC industry, the rating systems we use can be downright confusing. Well, we thought it would be a good time to review which rating systems you need to know as a client, and how they will impact the efficiency of the specific HVAC system you are buying. In this blog, we will look at furnaces, AC units, heat pumps, and filters, as well as the rating systems for these products.
Furnaces (Gas and Propane)- AFUE
For those looking to replace or install a new natural gas or propane furnace, you will want to pay attention to the Annual Fuel Utilization Efficiency (AFUE) rating. This metric determines how much fuel, whether it is natural gas or propane, is used to heat the home. The higher the rating, the more efficient your system will be. This is the calculation that is used to determine the specific AFUE of a unit:
- AFUE = (Total annual heat output in BTUs / Total annual energy input in BTUs) x 100
Per energy.gov, the AFUE ratings are split into three categories.
- A premium high efficiency furnace has an AFUE rating of between 95% and 98.5%
- A high-efficiency heating system has an AFUE rating of between 90% and 95%
- A mid-efficiency furnace will score between 83% and 90% on AFUE
- A standard-efficiency furnace will have an AFUE rating between 80% and 83%
No modern furnace should score below 80%, and if you have a furnace rated that low, it might be time to upgrade to a modern York, Carrier, or Rheem unit. One thing to note is that starting in December 2028, the US Department of Energy is mandating that all furnaces achieve a minimum AFUE of 95%. If you are looking to future-proof, you will want to opt for a premium high-efficiency furnace.
Air Conditioners and Heat Pumps- SEER and SEER2
While AFUE is the gold-standard rating for heating, the Seasonal Energy Efficiency Ratio (SEER) is the rating system used for heat pumps and AC Units. To get a unit’s SEER, divide the total heat removed from the home during the cooling season by the energy used during the same cooling season, in watt-hours. The HVAC industry has also adopted an upgraded rating system called SEER2, which tests units under more realistic conditions to reflect the unit’s actual efficiency in real-world use. Because the US has multiple climates, the standards will vary by region. Here in Toledo, OH, we are in the North, so the standards are:
- Split System AC Under 45k BTU/h – SEER 14 or SEER2 13.4
- Split System AC Over 45k BTU/h- SEER 14.4 or SEER2 13.4
- Single Packaged AC – SEER 14 or SEER2 13.4
- Split System Heat Pump – SEER 15 or SEER2 14.3
- Single Packaged Heat Pump – SEER 14 or SEER2 13.4
However, just like the AFUE rating, there are going to be SEER2 efficiency levels, with the standards as the lowest accepted rating. Here in the North region, the SEER2 scale is as follows:
- SEER2 13.4-15- The current legal minimum
- SEER2 15-17- Mid-efficiency systems that often are two-stage compressors and excellent humidity control.
- SEER2 18.0 +- High-efficiency cooling systems with variable-speed motors.
Filters- MERV
When you are looking for filters, choose one with a Minimum Efficiency Reporting Value (MERV) rating. The MERV measures the air filter’s ability to capture airborne particles between 0.2 and 10 microns in size. The higher the MERV rating, the more particulates the filter can capture.
- Basic Residential Filtration MERV 1-4: This level will trap larger particulates such as dust mites, pet hair and pollen.
- Standard Household Filtration MERV 5-8: This is the standard filter rating for most homes in Toledo, OH, and it can capture pet dander, fine dust, and mold spores.
- High-Efficiency Filtration MERV 9-12: For most HVAC units, this is the max MERV rating they can use, and these filters can trap smaller debris and particulates, including auto emissions and Legionella.
- Superior or Premium Filtration MERV 13-16: These filters are considered the crème de la crème and are able to capture bacteria, viruses and smoke particles to give you the purest air on the market.
One thing to note is that not all heating and cooling systems can accommodate high-MERV filters, so check your user manual or chat with a Fry expert to confirm what your specific furnace or air handler is designed to use.
As you can see, the rating systems for HVAC units and filters are not the most straightforward, but they are not rocket science either. If you have questions about a specific unit or want more information, the team at Fry is happy to help!
