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HVAC Rating Systems Explained

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If you’re shopping for a new HVAC system, you’re going to come across a lot of acronyms. For example, you might find yourself considering a heat pump with a SEER of 17. What does that mean exactly? Or maybe it’s a furnace with an AFUE of 89. What the heck is an AFUE?

It can be a little confusing.

Let’s break down common rating systems and what they mean for your comfort and wallet.


Stands for: Annual Fuel Utilization Efficiency

What it means: The AFUE measures how efficiently a furnace uses fuel. The AFUE number indicates the percentage of fuel that the furnace converts into heat. For example, if a furnace utilizes 85 percent of fuel, with the remaining going out the exhaust, then it would have an AFUE of 85

The scale ranges from 30 to 100. The federally enforced minimum standard for new units is 78. Higher-end models will be closer to 100, if not at 100.

If you’re in the market for a new unit, this rating can be a helpful factor in your decision to buy. However, you need to consider the fuel type. Natural gas is cheaper than electricity, but electricity is more efficient. Electric furnaces are the only models to achieve an AFUE of 100. So, while they are more efficient, they’ll be more expensive to operate.

In short, any furnace with an AFUE of 85 and above is going to be pretty top-of-the-line.


Stands for: Heating Season Performance Factor

What it means: This one applies to heat pumps. The HSPF number indicates the total heat output divided by how much energy the unit consumes in watt-hours.

The higher the HSPF, the more efficient the system’s heating performance.

Any heat pump manufactured after 2005 will have an HSPF of 7.7. Some of today’s most efficient models have an HSPF closer to 10.

If your existing system is older than 15 years, upgrading can save you a lot in the long run.


Stands for: Seasonal Energy Efficiency Ratio

What it means: The SEER measures an air conditioner or heat pump’s cooling efficiency. (Heat pumps, if you didn’t know, serve double duty as heating and cooling systems, so you’ll see both the SEER and HSPF listed on the label.)

When on cooling mode, a heat pump removes heat from a room. The SEER measures how much energy it takes the system to extract hot air.

New air conditioners and heat pumps must meet a minimum standard of SEER 13. The most efficient models have a SEER of around 20.

So, should you spring for a model with a high SEER? Maybe if you lived in Phoenix. This is Portland. We enjoy a comparatively mild climate here. A unit with a modest SEER of 13 or 14 would serve you well.


Stands for: Minimum Efficiency Reporting Value

What it means: The MERV rates the performance of a central air system’s filter. The smaller the particle the filter captures, the higher its MERV. The scale ranges from 1 to 16.

If you’re sensitive to allergies, or if indoor air quality is a particular concern, pay close attention to this rating.

A replaceable filter with a MERV of 1 to 4 will screen out such things as pollen, dust, and dust mites. Filters at the higher end of the scale will trap tobacco smoke, bacteria, and auto emissions.

Caveat: The higher the MERV, the harder your HVAC unit will work to push air through the screen.

A filter with a MERV of 6 to 13 will clean your air effectively without compromising the performance of your central air system.

Some filters are washable, so you won’t have to shell out money every month on a replacement.

Bottom line: Shopping for a new heating and cooling system can be a little complicated. We’re always happy to help explain these things in plain English so that you can make an informed decision. Questions? Call Morrison Heating & Cooling at (503) 683-7077.

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