Air Conditioner & Heater Energy Efficiency, Explained Simply

September 14, 2021

Translating All Those Confusing Technical HVAC Terms Into Plain English.

Have you been researching new heating or new air conditioning systems in Philadelphia and the suburbs? If so, you’ve likely seen several cryptic energy ratings and acronyms.

SEER. EER. AFUE. HSPF. These are all different types of energy ratings for heating and A/C units. And the labels that show these don’t provide much explanation as to what they are or what they measure.

But make no mistake: They are important. So we’re going to explain each of them in concise, “plain English” terms.

Let’s get started…

Energy Efficiency Ratio (EER)

Rates The Following System(s):

  • Air conditioners
  • Heat pumps

What It Measures:

EER rates the energy efficiency your system can achieve during peak cooling time (i.e., the hottest part of summer).
Calculating EER requires the following conditions:

  • 95°F outdoor temperature
  • 80°F indoor temperature with 50% relative humidity

EER is rated on a numerical scale. When considering a system’s EER rating, here’s the general rule of thumb:

  • 8 and lower: below-average efficiency
  • 8.5 to 9.5: average efficiency
  • 10 to 11: above-average efficiency
  • 11.5 and up: exceptional efficiency
energy guide HVAC

Seasonal Energy Efficiency Ratio (SEER)

Rates The Following System(s):

  • Air conditioners
  • Heat pumps when in cooling mode

What It Measures:

SEER rates the efficiency of a system over a warm season. It’s based on an average that is calculated using multiple tests with outdoor temperatures from 64°F to 104°F. The tests are performed with different levels of indoor humidity.

For moderate climates like Philadelphia, SEER is typically more important to consider than EER. Why? Because SEER measures efficiency under several conditions, while EER measures efficiency only under the hottest.

In our part of the country, the US Department Of Energy requires a minimum SEER rating of 13. The highest SEER rating is 26, which is extremely energy efficient.

Seasonal Energy Efficiency Ratio

Heating Seasonal Performance Factor (HSPF)

Rates The Following System(s):

  • Heat pumps when in heating mode

What It Measures:

Remember how SEER rates a cooling system’s efficiency over the course of a warm season? HSPF rates a heat pump’s efficiency over the course of a cold season.

The correlation between the HSPF rating and a heat pump’s efficiency is simple. A heat pump with an 8.7 HSPF will provide you with 8.7 British Thermal Units (BTUs) of heat for every kilowatt-hour (kWh). A heat pump with an 11.2 HSPF will give you 11.2 BTUs of heat for every kWh). And so on.

The higher the HSPF rating, the more energy-efficient the heat pump is. As you can see in the image on the right, the minimum acceptable HSPF rating is 7.1, while the most efficient heat pumps clock in at 10.2 or higher. To earn ENERGY STAR® certification, a packaged heat pump must have an 8.2 HSPF or higher and a SEER rating of at least 15.

Heating Seasonal Performance Factor

Annual Fuel Utilization Efficiency (AFUE)

Rates The Following System(s):

  • Gas and oil furnaces

What It Measures:

AFUE rates how much of a furnace’s fuel is converted to heat.

The rating itself is straightforward. A 78.0 AFUE rating means a furnace converts 78% of the energy in its fuel into heat. An 89.3 AFUE rating means a gas furnace converts 89.3% of its fuel energy into heat. And so on.

The minimum standard AFUE rating for gas and oil furnaces today is 78.0. The best of the best furnaces can achieve AFUE ratings of 98% and higher.

Annual Fuel Utilization Efficiency Energyguide

Recap Of These Heating & Cooling Energy Efficiency Ratings

  • EER: Rates the efficiency of air conditioners and heat pumps during peak cooling time. (Important for hot climates.)
  • SEER: Rates the average efficiency of air conditioners and heat pumps during warm seasons. (Important for moderate climates like Philadelphia and the suburbs.)
  • HSPF: Rates the average efficiency of heat pumps during cold seasons.
  • AFUE: Rates how much of a gas or oil furnace’s fuel is converted into heat energy.

Have Questions? Get In Touch

If you still find these ratings a little confusing, don’t worry. Simply call us, and we’d be happy to explain heating and cooling ratings in more detail.

Our mission at Philadelphia Gas & Electric Heating & Air Conditioning is to educate you, the homeowner, on your best options. That means a 100% fact, 0% pressure in-home appointment—guaranteed.