How to calculate energy efficiency of an air conditioner

As you can see from our blog on how to read an energy label, a split system air conditioner will ALWAYS output more energy than it consumes.

So how do we work out exactly how efficient a split system is, so we can compare products?

Well, there are two calculations:

1. This calculation in cooling mode is called EER (Energy Efficiency Ratio)
2. This calculation in heating mode is called COP (Coefficient of performance).

How to calculate EER (Cooling efficiency)

• In cooling mode, the air conditioner consumes 1.58kW and outputs 5.2kW.
• Divide the output (5.2kW) by the input (1.58kW).
• Therefore this split systems EER is: 3.41 to 1.
• This means the air conditioner will output 3.41 times as much energy as it consumes!

How to calculate COP (Heating efficiency)

• In heating mode, the air conditioner consumes 1.63kW and outputs 6.7kW.
• Divide the output (6.7kW) by the input (1.63kW).
• Therefore this split systems COP is: 4.1 to 1.
• This means the air conditioner will output 4.1 times as much energy as it consumes!

This sounds great, but how do I compare products?
The EER and COP readings are the easiest and fastest way for you to compare energy efficiency between air conditioners. Most reputable split system manufacturers include the EER and COP readings on their promotional material. Grab the most information you can get, and compare COP and EER's between products.

Conclusion
This co-efficiency is typical of most split system air conditioners and is the reason why split system air conditioning is one of the most energy efficient forms of heating and cooling available on the market today.

Resources

• Compare air conditioners through the Australian Government website
• Browse the Australian Governments' Energy Rating website
• Read about the Minimum Energy Perfomance Standards (MEPS)

Contact us!
At Ezy Air, we strive to provide our customers with the most relevant information to assist them to make the right decision. If you would like more information, please contact us by phone: 1300 EZY AIR (1300 399 247) or via our contact page!

How to read an energy label.

If you take a look at the above energy label, you will notice two red and two blue readings.
The top two readings (red and blue) represent the power output in heating and cooling modes.
The bottom two readings (red and blue) represent power input in heating and cooling modes.

• In cooling mode (top blue corner) - this air conditioner will output 5.2kW.

• In cooling mode (bottom blue corner) - this air conditioner will input 1.58kW.

• (For every 1.58kW you input, you output 5.2kW!)

• In heating mode (top red corner) - this air conditioner will output 6.7kW.

• In heating mode (bottom red corner) - this air conditioner will input 1.63kW.

• (For every 1.63kW you input, you output 6.7kW!)

As you can see, a split system air conditioner will output far more energy than it consumes!

How does a split system air conditioner work?

Split system air conditioners operate on a vapour compression refrigeration cycle. This is a thermodynamic process of refrigerant changing state (from a vapour to a liquid to a vapour again) which enables air conditioners to heat or cool.

Figure above: Condenser = 1, TX Valve = 2, Evaporator = 3, Compressor = 4.

1. Super Heated Vapour
We will start the example just before the compressor (No. 4), on the right hand side, where the refrigerant entering the compressor is a saturated vapour. After it goes through the compressor - it's compressed, so it's pressure and temperature of the saturated vapour goes up and it becomes a super heated vapour.

2. Sub Cooled Liquid
The super heated refrigerant is then forced through the condenser coil (No. 1), which has a fan blowing over the coils. This enables the heat to be released from the refrigerant. This process of cooling the refrigerant through the condenser brings the temperature of the vapour down and it changes state, to a sub cooled liquid.

3. Saturated Liquid
Before this sub cooled liquid reaches the evaporator (No. 3), a component inside the evaporator called the pressure release valve ( or TX valve - No.2) abruptly releases the pressure of the refrigerant. This abrupt pressure loss causes flash evaporation of some of the refrigerant and this brings the temperature of the refrigerant down again. The refrigerant is now a sub cooled, saturated liquid.

4. Saturated Vapour
This saturated liquid travels through the evaporator coil (No. 3). The evaporator fan sucks air over the coil and the refrigerant absorbs the heat from the coil. This causes the temperature of the refrigerant to go up, and the temperature of the air to go down. This heat exchange causes the refrigerant to boil and evaporate into a saturated vapour (keep in mind that R410A boils at minus 48.5 degrees, so it's still super cold).

And the Cycle Continues
The saturated vapour then travels through the refrigerant piping back to the compressor, where the refrigerant (in a vapour state) is compressed into a super heated vapour and the cycle continues.

Post Script
If you are learning about refrigeration for the first time. Please keep in mind that it took a colleague of the author, who has a Ph.D in plasma physics, magnetohydrodynamics & astrophysics around a year to get his head around vapour compression refrigeration... so don't sweat it if it doesn't make sense right now!

If you would like to research more on the matter, please follow the links to the following Wikipedia documents:
Wikipedia - Refrigeration
Wikipedia - Vapour Compression Refrigeration

Contact us!
At Ezy Air, we strive to provide our customers with the most relevant information to assist them to make the right decision. If you would like more information, please contact us by phone: 1300 EZY AIR (1300 399 247) or via our contact page!