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What Are Air Conditioning Efficiency, SEER, and EER?

Updated: Feb 1

Air conditioning efficiency is an important factor to consider when choosing a cooling system for your home or office. It not only impacts your comfort level but also your energy bills and environmental footprint.


What is the efficiency of an air conditioner and how can one calculate how efficient an air conditioner is?

To answer these questions you have to find out your efficiency or what efficiency you’re trying to achieve. Your efficiency is determined by two different equations: SEER and EER.


When determining efficiency I like to look at EER for that is how efficient an air conditioner is at a given time, and SEER is how efficient it roughly is throughout an entire season. EER shows how much energy consumed is converted into BTUs.


What is SEER?

SEER, which is an acronym for seasonal energy efficiency rating, is a measurement used to describe the efficient use of energy by air conditioners. The measurement is defined and regulated by the Air-Conditioning, Heating and Refrigeration Institute.


It is measured in BTUs (British thermal units) per watt-hour of electric energy used in a given cooling season (during the summer months). SEER is determined by calculating a simple equation.


IN SHORT, IT MEANS HOW MUCH ENERGY USED PER COOLING CAPACITY THROUGHOUT AN ENTIRE COOLING SEASON.


How to calculate Seasonal Energy Efficiency Rating (SEER)


Step 1

Find the BTUs per hour of your air conditioner. This value can be found either on the air conditioner itself or in the owner’s manual that accompanies the air conditioner.


Step 2

Find the number of watts used per hour for your air conditioner. This value can be also found either on the air conditioner itself or in the owner’s manual that accompanies the air conditioner.


Step 3

Calculate the number of BTUs used in the summer months. Use 1,000 hours, which equates to about 125 days or four months, to represent the late spring and summer months when air conditioners are used. Multiply the number from step one by 1,000 to get the number of BTUs used in the summer months.


Step 4

Calculate the number of watts-hours used in the summer months by multiplying the number from step two by 1,000.


Step 5

Divide the BTUs used in the summer months (the result of step three) by the number of watts-hours consumed in the summer months (the result of step three) to arrive at the SEER rating.



What is EER?

The Energy Efficiency Ratio – EER – is a term generally used to define the cooling efficiency of unitary air-conditioning and heat pump systems.


The efficiency is determined at a single rated condition specified by an appropriate equipment standard and is defined as the ratio of net cooling capacity – or heat removed in Btu/h – to the total input rate of electric power applied – in Watts. The units of EER are Btu/Wh.


How to Calculate Energy Efficiency Ratio (EER)


EER = Ec / Pa (3)


where


EER = energy efficient ratio (Btu/Wh)

Ec = net cooling capacity (Btu/h)

Pa = applied electrical power (Watts)


This efficiency term typically includes the energy requirement of auxiliary systems such as indoor and outdoor fans.


higher EER – more efficient system


*IN SHORT, IT MEANS HOW EFFICIENTLY YOUR AIR CONDITIONER CAN COOL YOUR HOME PER WATT throughout an entire season.


Key Differences between EER and SEER


EER (Energy Efficiency Ratio):


  • Measures the efficiency of an air conditioner or heat pump at a single operating point, usually a fixed temperature and humidity level.

  • Calculated as the ratio of the cooling output (BTU) to the electrical energy consumed (watt-hours) at that specific point.

  • Useful for comparing the peak efficiency of different units under similar conditions.

  • Doesn't consider the variations in temperature and humidity that occur throughout a cooling season.


SEER (Seasonal Energy Efficiency Ratio):

  • Measures the average efficiency of an air conditioner or heat pump over an entire cooling season.

  • Takes into account a range of operating conditions, including different temperatures and humidity levels, based on your specific location.

  • Calculated using a standard test procedure that simulates an average cooling season.

  • More representative of real-world performance and energy consumption than EER.

  • Used to compare the overall efficiency of different units and estimate annual energy costs.


In summary:


EER

SEER

Focuses on:

Efficiency at a specific time

Efficiency over a season

Considers:

Temperature and power at one moment

Varied temperatures and power usage throughout the season

Useful For:

Comparing efficiencies at peak cooling times

Choosing an air conditioner for long-term use


Contact Integrity Air Heating & Cooling Specialist for an Assessment

Not sure how to calculate these numbers yourself? We have you covered. If you're concerned about your HVAC system's energy efficiency, contact Integrity Air Heating & Cooling Specialist to see how we can help you.

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