Download Full Report

HOW IS CEER DIFFERENT FROM EER?

The CEER is not just another code name for EER; it is fundamentally different and yields a much lower rating than the same unit’s EER. The Combined Energy Efficiency Ratio (CEER) is the standard metric for measuring the energy efficiency of room air conditioners. Unlike the older EER, which measured efficiency only while the unit was cooling, CEER accounts for energy consumed when the unit is in standby or off mode.

To calculate CEER, you must factor in the cooling capacity, the active power consumption, and the “phantom” power draw during the rest of the year. EER is simply calculated by dividing the BTU by the power draw. EER = Capacity ÷ Watts.

The CEER Formula

The standard calculation is:

CEER = (Capacity × Hours_active) ÷ [(Watts_active × Hours_active) + (Watts_standby × Hours_standby)]

Where:

Capacity: Cooling capacity in BTU/h.

Hours_active: The estimated number of hours the unit is cooling (standardized at 750 hours).

Watts_active: The power consumption while cooling (Watts).

Watts_standby: The power consumption in standby/off mode (Watts).

Hours_standby: The remaining hours in the year assigned to the cooling season (standardized at 5,115 hours).

Step-by-Step Calculation Example

Let’s calculate the CEER for a window AC unit with the following specifications:

Cooling Capacity: 8,000 BTU/h

Power Consumption (Active): 700 Watts

Power Consumption (Standby): 1.5 Watts

1. Calculate Total Cooling Output

First, determine the total BTUs delivered during the active cooling season (750 hours):

8,000 \text{ BTU/h} \times 750 \text{ h} = 6,000,000 \text{ BTUs}

2. Calculate Total Energy Consumed

Next, calculate the total Watt-hours ($Wh$) consumed both while active and while in standby:

Active Energy: 700 \text{ W} \times 750 \text{ h} = 525,000 \text{ Wh}

Standby Energy: 1.5 \text{ W} \times 5,115 \text{ h} = 7,672.5 \text{ Wh}

Total Energy: 525,000 + 7,672.5 = 532,672.5 \text{ Wh}

3. Divide Output by Total Input

Finally, divide the total BTU output by the total Watt-hour input:

CEER = 11.26

Most importantly: CEER is always lower than EER. In the above case, the CEER is 11.26; the EER would be 11.43.

Summary Table: CEER vs. EER

FeatureEER (Energy Efficiency Ratio)CEER (Combined EER)
MeasurementInstantaneous efficiencySeasonal efficiency
Modes IncludedCooling Mode onlyCooling + Standby + Off
Typical ValueUsually higherUsually slightly lower
PurposePeak load performanceTotal annual energy cost
swipe to see more