Efficiency Ratings Explained

Energy Efficiency

Efficiency ratings are generally a measure of how much power is lost between the wall plug and your machine. That’s overly simplified, but in general, you are looking at how much power your appliance uses to reach the maximum efficiency of the machine and how much of that is wasted.

In most cases, you will find that each kind of rating is paired to a specific HVAC type appliance, and some may not apply to your situation.

What are the Most Common Efficiency Ratings

Below, we will list the most common efficiency ratings and give explanations for non-professionals. These ratings are used on different appliances, from air conditioners to furnaces.


SEER stands for Seasonal Energy Efficiency Ratio (SEER). It is usually used for central air HVAC systems. It measures an appliance’s efficiency based on changing temperatures. It looks at a temperature range that represents a season, from 64 degrees to 104. The higher the number, the more efficient that unit is at using energy to maintain the temperature in your house.

That means less energy is wasted, and you spend less on power to get the results you want.


AFUE stands for Annual Fuel Utilization Efficiency. This number is not one you are likely to find on an air conditioner, as it is used for furnaces that are powered by gas or fuel oil. This number is given as a percentage. In simple terms, it informs you what percent of the fuel used is converted to energy and how much is lost as heat or through inefficiency.

If your AFUE is below 60 percent, you should consider replacing your furnace. It may be a bit expensive to do, but you can expect about a 40 percent reduction in fuel costs.


HSPF stands for Heating Seasonal Performance Factor. It is a rating used for air source heat pumps and, in some cases, other furnaces or heating appliances. It measures energy used against heat produced, so it is BTUs (British Thermal Units, a measure of heat) produced divide by watts of electricity per hour (kWh). The higher the number, the better the unit is at producing heat with the energy it uses.

10 is the highest number for this rating, so the best choice. Heat pumps that have a 10 will produce 10 BTU per kWh.


EER stands for Energy Efficiency Rating. It differs from SEER in that SEER ratings are for an entire season and temperature range, but EER is for one temperature. EER ratings are based on a single known temperature, 95 degrees. This makes them basically a snapshot in time showing the best performance at a constant temp.

An average rating for EER is 8.5, so anything above that is a good choice.


IEER stands for Integrated Energy Efficiency Ratio. This rating is used for split systems and is not often used by non-professionals. It measures the efficiency of the machine, as EER does, but under a range of circumstances and temperatures. To get an IEER rating, you need four separate EER numbers.

What These Ratings Mean to You

Understanding different efficiency ratings will help you to make good decisions throughout the lifetime of your appliance. Not to mention, this knowledge will help you choose the right one for your needs when it is time to purchase one. Energy costs the average Tennessee resident 2.2 percent of their annual income, which is about $1,200 a year if you make $60K.

If you are looking for professional HVAC help in the Pittsburgh area, call One Hour Heating and Air Conditioning to request an appointment.