How to Identify Energy Efficient Air Conditioners

As summer approaches and temperatures rise, homeowners and businesses can expect an increase in energy bills due to air conditioning. Space cooling is the biggest electricity expense in most homes and commercial buildings, and energy consumption increases along with the outside temperature.

Summer energy bills can be greatly reduced with an air conditioning upgrade, but only if you buy the right product. Any AC manufacturer can claim to offer high-efficiency units, but you can only be sure if they are certified by a neutral third party.

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The best starting point is to look for air conditioners with the ENERGY STAR Label , which have been independently tested to U.S. EPA standards. However, there are performance differences even between labeled units: by familiarizing yourself with the different energy efficiency ratings, you can know exactly what performance to expect.

Understanding Energy Efficiency Ratings for Air Conditioners

Depending on the type of refrigeration equipment, you may find different energy efficiency ratings in the technical specifications. When comparing ENERGY STAR air conditioning systems you will find five main metrics, which are summarized in the following table:

These five values ​​have different calculation procedures, but their basic principle is similar: they indicate a relationship between cooling output and electricity input, similar to the miles per gallon (MPG) of a car.

The Combined Energy Efficiency Ratio or CEER is used for window-type air conditioners, also known as room air conditioners. CEER is a metric that indicates the cooling power in BTU, considering the input power in all operating conditions. This means that CEER considers both electricity consumption when the compressor is running, and standby consumption when the compressor is off.

The Seasonal Energy Efficiency Index or SEER is an efficiency metric that considers the entire cooling season, which makes it useful for estimating annual electricity costs. SEER is used for unitary air conditioners other than window or PTAC type, and also for air source heat pumps in cooling mode.

The Integrated Energy Efficiency Index or IEER is similar to SEER, but was developed for larger commercial units with varying workloads. IEER can be described as a weighted efficiency value that considers various operating conditions and workloads:

• 95.0°F ambient temperature, 100% load, 2% operating time
• Ambient temperature 81.5°F, 75% load, 61.7% operating time
• 68.0°F ambient temperature, 50% load, 23.8% operating time
• 65.0°F ambient temperature, 25% load, 12.5% ​​operating time

The ENERGY STAR program uses SEER for equipment below 65,000 BTU/hour of cooling capacity, and IEER for equipment larger than 240,000 BTU/hour.

The Energy Efficiency Index or EER is similar to SEER and IEER, but considers a single operating condition: 95°F outdoor temperature, 80°F indoor temperature, and 50% relative humidity. The EER can be used for all refrigeration equipment, which means you can compare different types of air conditioners. However, the main disadvantage of EER is that it only reflects performance for a specific operating condition, and AC units in buildings are exposed to a wide range of temperature and humidity levels.

Coefficient of Performance or COP is also a general performance metric, which can be used for cooling and heating. Unlike the previous four metrics, which assume cooling output in BTU and electricity input in watt-hours, COP uses the same units for energy output and input. COP is often used to describe the performance of geothermal heat pumps, which do not have a dedicated rating such as CEER, SEER or IEER.

ENERGY STAR Minimum Efficiency Requirements for Air Conditioners

The ENERGY STAR program has several technical requirements for HVAC equipment , which include a minimum efficiency rating. There is an extensive list of requirements for air conditioning manufacturers wishing to obtain the label. The following table summarizes the efficiency requirements:

If you are considering an air conditioning upgrade, the best recommendation is to look for an ENERGY STAR unit with the highest efficiency rating possible. Just keep in mind that the efficiency metrics used change depending on the type of AC equipment.