AC System SEER Ratings

UNDERSTANDING SEER

Having a basic understanding of the air conditioning and heating manufacturer’s ratings will help prepare you for your purchase and arm you with the tools needed to make a more informed decision.

What is Seer?

Every air conditioning unit is given an efficiency rating known as SEER, which stands for “seasonal energy efficiency ratio.” The SEER rating is calculated by dividing its total electrical energy input (in Watt-Hours) during the cooling season by its total cooling output (in British Thermal Units) during the cooling season.

SEER = total energy input ÷ total cooling output

A higher SEER rating means greater efficiency, and thus more savings in energy costs. Government regulations for heating and cooling are in place to increase efficiency and reduce energy output. In January 2006, the U.S. Department of Energy mandated that new air conditioners manufactured in the United States must have a minimum SEER rating of 13.

Calculating Energy Usage With SEER

To determine the energy usage of an air conditioning unit, first determine the SEER rating. A unit with a SEER rating of 13 will produce 13 British Thermal Units (BTUs) of cooling per Watt-Hour (Wh). If your current unit has a SEER rating of only 10, it is consuming more energy and is less efficient than the 13 SEER unit because it produces only 10 BTUs of cooling for the same Wh of operation.

Ensuring Maximum Efficiency

Proper installation is imperative to guarantee that a unit is performing at its certified efficiency rating. A good install will eliminate air leakage, as well as ensure correct layout, insulation and adequacy of the duct system. When choosing an installation professional, look for a qualified contractor who can verify that the system is properly “matched” and achieves its certified energy efficiency rating. With a system that is matched correctly, the indoor (coil) unit and outdoor (condensing) unit will work together as intended and perform at maximum efficiency. Ask your contractor to provide you with an AHRI Reference Number, or a Certificate of AHRI Certified Performance for verification.

Now that you have a good understanding of SEER, let’s define some of the other terminology that goes hand in hand with calculating heating/cooling operating costs.

What is BTU?

BTU is a measure of heat energy that stands for British Thermal Unit. One BTU equals the amount of heat energy needed to increase the temperature of one pound of water by one degree Fahrenheit. In relation to air conditioning, BTU refers to lowering the temperature rather than raising it. An air conditioner’s capacity is measured in BTUs per hour. An air conditioner with a capacity of 10,000 BTU per hour can remove enough heat from the air to lower 10,000 pounds of water one degree Fahrenheit each hour.

What is Wh?

Watt hours (Wh) measure the amount of electrical energy produced or the amount of electrical energy consumed. An air conditioning system's total Wh refers to the energy exerted to run the system for one hour. For example, if you turn on a 60 watt light bulb for an hour, you've used 60 Wh of energy.

What is AFUE?

AFUE is the standard measurement of efficiency for gas and oil-fired furnaces. AFUE stands for Annual Fuel Utilization Efficiency. The AFUE percentage indicates how much of the fuel you supply to the unit is used to heat your home and how much fuel is lost. The higher the AFUE rating, the greater the efficiency. For example, if your furnace has 60% AFUE rating, it is converting 60% of its fuel to heat while the remaining 40% is wasted. Most furnaces today have an AFUE rating of 80%.

What is HSPF?

The Heating Season Performance Factor, or HSPF, is a seasonal measure for the heating efficiency (usually of a heat pump) for an entire heating season. A heating unit’s HSPF is equivalent to an air conditioner’s SEER rating. The higher the number, the greater the efficiency and cost-savings. In 2005, The U.S. Department of Energy required that newly manufactured central heat pumps have a minimum of 7.7 HSPF. This number can be calculated by dividing the total annual heating requirements by the total electric power used.

SEER Rating Annual Savings Chart