In the Energy Star certification program for room air conditioners, there is Section 3: Core Qualification Criteria that states:
“CEER shall be greater than or equal to the Minimum CEER (CEERmin) as calculated per Equation 2.”
If you open a window AC unit’s specification sheet, you will likely see the CEER rating between 8-15. Here is the yellow EnergyGuide label of LG LW1517IVSM 14,000 BTU window air conditioner that specifies the CEER ratio:
Here we will explain exactly what CEER rating is and why it is such an important metric in regard to window air conditioners.
We will also explain what is a good CEER rating for an air conditioner. At the end, you can find a CEER chart that plainly shows you what is a good CEER rating and, even more importantly, what is the minimal requirement for CEER rating for that particular AC to be awarded Energy Star certification.
What Does CEER Rating Actually Mean?
CEER rating stands for ‘Combined Energy-Efficiency Ratio’ rating. It is one of the key energy-efficiency metrics we use to adequately evaluate how much electricity an air conditioner will spend. Other similar ratings are the older and more commonly used are EER and SEER for mini-splits.
CEER is defined as ‘The ratio of measured cooling output (in BTU per hour) to measured average electrical energy input (in Watts) and measured standby/off-mode power consumption (in Watts.).’
In short, the CEER rating measures how many BTU/hr our AC generates given how much power we provide it during normal operation AND during the standby/off-mode. The key here is that CEER takes into account the standby/off-mode electricity usage as well as the normal operation power usage.
Let’s clearly illustrate (in simplified terms) the difference between EER, SEER, and CEER in air conditioners. These energy-efficiency specifications measure BTU/hr output at different AC settings (Standy Mode, Speed 1, Speed 2, Speed 3, etc.):
- EER Rating: 100% BTU output.
- SEER Rating: 100% BTU + 75% BTU + 50% BTU + 25% BTU output.
- CEER Rating: 100% BTU + Standby/Off-Mode BTU output.
CEER is Combined EER because of the addition of energy usage in the standby/off-mode.
Department of Energy has introduced the CEER rating in June 2014 to better estimate the overall realistic energy-efficiency of room air conditioners.
How DOE Actually Calculates CEER Rating
The point of the CEER rating is that it includes the standby/off-mode energy consumption according to the DOE room AC test procedure in 10 CFR 430, Subpart B, Appendix F.
To derive the CEER rating formula, DOE has conducted a statistical analysis of how much power room air conditioner use while in standby and off mode. Here are the numbers that seem from this analysis:
- Average standby power input is 1.4 Watts.
- CEER presume 750 operational hours (100% BTU output).
- CEER presumes 5115 hours of standby mode.
The key element that EER doesn’t account for and the CEER rating does is the 5115 hours of standby mode, using 1.4 W of energy. Most of this 1.4 Watts energy comes from the transformer. In fact, according to the DOE, “transformer power consumption accounts for about 75 percent of the power draw”.
Compared to EER, the combined energy-efficiency ratio rating takes into account a broader range of AC operations and thus more fully describes how much electricity an AC unit will require to generate a certain cooling output (measured in BTU/hr).
Why It’s Useful To Even Check The CEER Rating?
When buying an air conditioner, it’s always useful to have in mind the old HVAC saying:
“The most expensive air conditioner is a cheap one with low energy-efficiency.”
The true cost of every air conditioner is not the unit itself; it’s the electricity usage. If you use a window air conditioner for 10 years, the cost of electricity you use can be several times higher than the initial cost of the unit.
CEER rating tells you (quite accurately) which air conditioner is the most energy-efficient. The higher the CEER rating, the less electricity you’ll have to pay for the same amount of cooling output.
If in doubt, it’s recommended to always pick an AC unit with a higher CEER rating, even if it costs several $100 more. To illustrate, we have done some cost-effectiveness calculation using the CEER rating:
What Is A Good CEER Rating For Air Conditioner?
An air conditioner with a high CEER rating can generate quite a lot of electricity savings. To illustrate this, let’s compare the energy usage of two 14,000 BTU window air conditioners with different SEER ratings:
Case of a high CEER rated unit: LG LW1517IVSM 14,000 BTU has an extremely high 14.7 CEER rating. Rated yearly electricity expenditure is thus $68.
Case of a low CEER rated unit: A cheaper 14,000 BTU has a low 9 CEER rating. Rated yearly electricity expenditure is thus $111.
As we can see, the difference in electricity usage between the high CEER and low CEER air conditioner is $43/year, and that’s for the absolute minimum air conditioner usage. Practically, the difference in cost would be more than $100/year. You can check different kinds of high CEER air conditioners (expressed either in CEER, EER, or SEER ratings) here:
- Best portable air conditioners with a high EER rating.
- Most energy-efficient ductless mini-split AC units.
- Most energy-efficient window air conditioners.
Now, window air conditioners easily last for 10 years or more. In 10 years, the higher CEER unit will use 10 years x $43/year = $430 less electricity compared to the low CEER rated air conditioner. You can check how long do air conditioners last here.
That’s quite a lot, and this is the minimal difference. If a high CEER unit would cost $500 and a low CEER unit would cost $200, choose the more expensive high CEER unit still makes much more sense financially.
To look exactly at what CEER rating is good for a given air conditioner, let’s look at the CEER rating chart:
CEER Rating Chart
Energy Star certified air conditioners are among the top 10% of the most energy-efficient AC units in their respective category. Any AC unit that is to be awarded the Energy Star certificate has to achieve a certain minimal CEER rating to qualify for the certification.
Based on this CEER rating table, we can clearly draw a line between high CEER rated and lower CEER rated air conditioners. Here is the CEER rating chart for air conditioners with certain capacity (expressed in BTU):
| Cooling Capacity (BTU) | Min. CEER Rating |
|---|---|
| Below 8,000 BTU | 11.0 |
| 8,000-14,000 BTU | 11.2 |
| 14,000-20,000 BTU | 11.1 |
| 20,000-28,000 BTU | 9.8 |
| 28,000 BTU and above | 9.8 |
Based on CEER, EER, and SEER we can look at 100s of different air conditioners and rank them from the most efficient to the least efficient. We use these ratings as primary ranking factors in a number of our articles and best-of lists, including:
- Best vertical AC units for casement windows.
- Best window air conditioners (EER and CEER rating combination).
- Small air conditioners (for small rooms).
- Quiet window air conditioners.
- Best through the wall air conditioners.
- (Partly) ranking central air conditioner brands.
- Cheapest portable AC units (energy efficiency is the key there).
- Best tent air conditioners.
- Over the sill air conditioners (Midea U Inverter, for example, has a CEER rating of 15).
- Best dual-hose portable AC units (two hoses increase EER and CEER ratings).
- AC units with specific BTU output, including 5,000 BTU, 8,000 BTU, 10,000 BTU, 12,000 BTU air conditioners.
- Biggest portable AC units.
- Best portable air conditioners for apartments.
The bottom line is this:
CEER rating is the newest energy-efficiency metric for air conditioners that include the energy expenditure in the standby/off-mode. That’s why it’s more accurate than the EER rating.
If you have any questions regarding the CEER rating, you’re welcome to pose them in the comments below.
I am looking at the same unit you discussed! LG 14,000 BTU/hr inverter window AC model LW1517IVSM lists CEER as 14.7, but I also see it listed with an EER of 11.2. For non-inverter models EER seems to normally be very close (but higher than) CEER, so is there some “trick” with inverter units compared to conventional? Note that LG lists this model as1240 watts, and 11.3 A @ 115V, which is consistent with an EER of 11.2, but the wattage and amps are “high” for the CEER of 14.7 as I understand it. ??
Hello Ted, the “trick” is basically the difference in how rotary (non-inverter) and inverter compressors work. Inverter compressors are constantly optimizing for the perfect temperature while rotary ones just kick in when the temperature is a few degrees off. That rotary compressor kicking in is inefficient compared to constant inverter compressor running; hence the difference is CEER, and no difference in EER.
The inner workings are a bit technical but this is the gist of it.
I hate how they no longer list EER which is the honest rating. SEER was a mockery with some of these units listing 20 to 33 when in fact their EER was around 11, which meant 1364 watts at 15,000 BTU/hour cooling.
Hello George, EER rating really is the honest rating. It’s just BTU output divided by max. wattage; that’s pure numbers. These SEER and CEER ratings, however, try to encompass the realistic electricity expenditure.
Agreed! I live off grid and need to be able to figure out wattage useage. This stupid ceer I have to make sure I deduct 7161 (1.4 watts × 5115 hours) before I can figure out actual wattage drain on my solar system. Seriously? Some engineer thought we needed to add that extra 1.4 watts?
Hello Kathryn, engineers are trying to best evaluate energy efficiency in real-time conditions. EER might be simple but it’s unrealistic. With that said, the CEER rating is not exactly a rating that would add a lot to the current EER rating.
EER is vital and should still get published with CEER/SEER.
CEER has little meaning in my application. The unit will NOT be in standby mode for 5000 hours. It would only get plugged in during a power-outage event where my batteries + solar & small generator won’t allow my whole house fixed AC to turn on due to to the initial current draw.
I have a ductless mini split that cools a small area of my home that I can use during the day since it is smaller/lower draw. It will keep part of the house “habitable” when it is 110 degrees outside. I plan to use a portable unit to cool the master bedroom at night. During non-use times it would be unplugged from the wall so no 1.4W draw.
As an engineer I always advocate for full access to the numbers so they can be used appropriately. Anyone else trying to “think for me” is likely not going to be using the right assumptions making their conclusions invalid.
Hi Gary, completely agree with publishing all the ratings. However, most producers will probably just focus on the ratings that they have to report. So, on specs sheets, you will start to see CEER more often than EER. Both should be included for the most comprehensive understanding of energy efficiency.