Chiller Energy Performance

Tons of Refrigeration (TR)

One ton of refrigeration is the amount of cooling obtained by one ton of ice melting in one day the uniform melting of one ton (1000kg) of ice and at 00C in 24hr. 



                                                                1TR= 12000BTU/hr

Coefficient of Performance

It is a measure of chiller output (cooling) Divided by Input (Electric Power), Typical Valves are 2-4.

COP= Cooling Effect Produce (KW)/ Power Input (KW)


It is a ratio of power input to compressor divided by tons of cooling produced, Lower the iKW/TR indicates higher efficiency. iKW/TR is used as a reference energy performance indicator.

Energy Efficiency Ratio (EER)

EER is calculated by dividing a chiller cooling capacity in BTU/hr by Power input in watts at full load conditions. Typical Valves are 8-10. The higher EER, the more efficient unit. 

This valve shows efficiency when operating at peak load capacity.

EER = COP x 3.4

Integrated Energy Efficiency Ratio (IEER)

This value is more representative of the actual efficiency you will get out of your HVAC equipment. To calculate this value, efficiencies are reported at different loads (outdoor temperatures ranging from 65 to 95 degrees F) and then given weights to obtain an overall efficiency value.

IEER = (0.02 * A) + (0.617 * B) + (0.238 * C) + (0.125 * D)


A = EER at 100% net capacity at AHRI standard condition (95 deg F)

B = EER at 75% net capacity and reduced ambient (81.5 deg F)

C = EER at 50% net capacity and reduced ambient (68 deg F)

D = EER at 25% net capacity and reduced ambient (65 deg F)

Seasonal Energy Efficiency Ratio

As same EER But representative measurement of how the system behaves over a season where the outdoor temperature varies. It is the ratio of output cooling energy in BTU over a season to input electrical energy in watts during the same season.

Integrated Part Load Valve (IPLV)

It expresses part-load efficiency for Chiller, based on the weighted operation at various load capacities. It is most commonly used to describe the performance of chiller modulation.

Unlike an EER, or COP, which describes the efficiency at full load Conditions, the IPLV is derived from the equipment efficiency while operating at various capacities. Since a chiller does not always run at 100 % capacity, the EER or COP is not an ideal representation of the typical equipment performance. The IPLV is a very important valve to consider since it can affect energy usages and operating costs throughout the lifetime of the equipment.

 IPLV is Calculated Under a variety of conditions when the unit is operating at 25%, 50%, 75%, and 100% of capacity and at different temperatures.

As per AHRI 551/591 (SI) 2018 Standard

                                 IPLV = 0.01A + 0.42B +0.45 C + 0.12 D


A= COP or EER at 100 % capacity

B= COP or EER at 75 % capacity

C= COP or EER at 50 % capacity

D= COP or EER at 25 % capacity

Non Standard Part Load Valve (NPLV)

If a chiller is designed to operate at different conditions than specified in AHRI 550/590, Including lower water temperature or different water flow rate, the efficiency is called an NPLV. It can be calculated by the same equation as above.

Chiller Matrix

This  Chiller Matrix Provide iKW/TR for Different Condenser Entering Water Temperatures and loading Conditions as shown below.

Chiller Energy Performance Parameters
Chiller Matrix

AHRI Conditions

Standard reference conditions at which chiller performance is measured, as defined by the air conditioning and refrigeration Institute (ARI)

Water Cooled chiller is required to run at 44 Deg. F evaporator Leaving water temperature with a flow rate of 2.4 GPM/ Ton.

The condenser entering water temperature will vary depending on the part load capacity utilizing a 3 GPM/Ton flow rate, and 85 Deg. F at 100 % Load.

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