Air conditioning ratings

Are ENERGY STAR units always the most efficient?

Most websites on air conditioning ratings will recommend you buy an ENERGY STAR rated air conditioner. These energy saving air conditioners will undoubtedly save you money compared to the cheapest, least efficient on the market (since the ENERGY STAR ones will be at least 10% more efficient).

ENERGY STAR air conditioners will definitely be more efficient than anything more than 8 or 10 years old, because as mentioned in my overview article Energy saving air conditioners, efficiency requirements keep rising, and because old air conditioners can become less efficient with time. They will also be more efficient than a unit with the same BTU rating but that is not ENERGY STAR rated.

If you’re looking for an efficient air conditioner for a room, however, the real challenge is that, as a rule, room air conditioners aren’t built for efficiency. They are built to provide relief from heat at a low sticker price. Out of thousands of room air conditioners, only 73 room air conditioners have air conditioner ratings that qualify them for an ENERGY STAR rating.

Let’s start in the 5,000 to 5,999 BTU range, for which I can find, as of December 2023, 189 different products available on Amazon.com. How many of those show up in ENERGY STAR’s list of 73 room air conditioners?

Zero.

What about in the 5,999 to 7,999 range?

One. The LG Room Air Conditioner model LW6023IVSM.

The latest ENERGY STAR standards for room air conditioner ratings were established in December 2020 – three years ago as of writing. So manufacturers have had plenty of time to get cracking making air conditioners that meet or exceed the specifications. Very few appear to have done so.

The most common BTU size for an ENERGY STAR room air conditioner is 12,000 BTU – there are 23 air conditioners that meet the ENERGY STAR requirement. But 12,000 BTU is overpowered for most individual rooms; it’s more suited for a bachelor appartment or multiple rooms connected by a wide opening. Energy consumption for these units ranges from an estimated 592 kWh per year for the most efficient, to 677 kWh per year for the least efficient. That’s a 14% range within ENERGY STAR alone.

When looking at air conditioner ratings for room air conditioners, given that ENERGY STAR rated room air conditioners are so scarce, you can at least look for units with the highest Combined Energy Efficiency Ratio or CEER. The air conditioner ratings contained in the ENERGY STAR specification as of 2020 require the following CEER rating minimums:

The above is for units without a reverse cycle (meaning, units that can heat as well as cool). For units with reverse cycle, the CEER requirements are all within the 9.6 to 10.8 range.

Remember. Don’t take a salesperson’s or a product listing’s word on energy efficiency – they’re in the business of selling what they have to sell! That means:

1. Insist on seeing the government-approved energy efficiency tag on any air conditioner you are thinking of buying, and don’t take the sales person’s word that “It’s very efficient” since this doesn’t tell you what you need to know.
2. Watch for claims of ENERGY STAR certification without a visible ENERGY STAR logo. On Amazon listings, if you see a field “ENERGY STAR” with a value “5 stars” that is almost certainly a guarantee that the product is not an ENERGY STAR air conditioner.
3. Don’t buy from an agent who tries to tell you that buying an energy saving air conditioner is a waste of money. Between a window unit costing $300 that is at the CEER standard, and another costing $375 that is 12% better than the standard and is therefore ENERGY STAR designated, you will save the difference in cost in just eight years assuming you pay $0.15 per kilowatt hour.

Do your own research online and find out how close the models you’re considering for purchase are from the highest possible CEER rating. Given how much electricity even a 5,000 BTU room air conditioner can consume in one cooling season, you want to get the most energy saving air conditioner you can.

And remember that even though the large majority of the air conditioners you will see have a CEER rating of not much higher than the Federal standard (between 9.5 and 10.5 depending on the capacity and the age of the unit), there are air conditioning systems out there with CEER ratings as high as 14. While they are hard to find, if you use AC a lot they will pay for themselves quickly.

Central air conditioning ratings

The story for central air conditioners is markedly different. There are 378,167 central air conditioner models that meet the ENERGY STAR standard. Wait, what? That’s roughly 5,180 central air conditioners with an ENERGY STAR rating for every room air conditioner with an ENERGY STAR rating. How is that possible?

The answer is likely that, since people buying a whole house air conditioner know they will be spending a lot more operating the unit, and since they typically have the time to plan a purchase and shop around, manufacturers have a strong incentive to provide a range of efficiencies within the ENERGY STAR range.

And the range of air conditioner ratings for central air conditioners is much broader than for room air conditioners. Within the ENERGY STAR category, SEER ratings go from 15.2 to as high as 25.8.

Top rated central air conditioners from an efficiency point of view are:

• Carrier Evolution Extreme
• Carrier Infinity with Greenspeed Intelligence
• Dave Lennox Signature Series

These all have air conditioning ratings in the CEER 23-24 range. On a side note, I purchased a Carrier Infinity Heat Pump with Greenspeed Intelligence – it’s basically an air conditioner that can also run backwards in the winter and heat my home very affordably – and I’ve been very happy with it. For more information see my article on High Efficiency Heat Pumps.

SEER and CEER ratings

Air conditioner ratings are sometimes provided in a Seasonal Energy Efficiency Rating (SEER) rather than the standard CEER (Combined Energy Efficiency Rating). Here’s the difference:

• CEER rates the energy efficiency of an air conditioning unit by looking at the ratio of output cooling (in BTU/hour) to the input power in Watts over an extended period of time (which helps factor in things like power consumption during standby mode when the air conditioner is not operating) and for a given temperature difference between inside and outside
• SEER measures the ratio over an entire cooling season, and considers a range of temperature differences assuming seasonal fluctuations in outdoor temperature.

CEER replaces the older EER, and in some product descriptions you will see EER mentioned instead of CEER. Both are measures of the energy efficiency of air conditioners, but they are calculated slightly differently.

The Energy Efficiency Ratio (EER) is a measure of air conditoiner efficiency at a specific outdoor temperature (usually 95°F or 35°C). The formula is simply (BTU of cooling capacity) / Watts.

The Combined Energy Efficiency Ratio is an average efficiency rating that takes into account the performance of the air conditioner at different operating conditions. It considers part-load performance, which is important because air conditioners often operate at less than maximum capacity, as well as standby mode when the air conditioner is drawing power but not providing cooling. The CEER is a weighted average of the EER values at different operating points. Think of it as a weighted sum of EER ratings at different output levels.

CEER values are typically a little lower than EER values because CEER accounts for a range of operating conditions. EER provides a snapshot of efficiency at peak power, while CEER gives a more realistic view of efficiency in a range of conditions.

SEER values are usually reserved for larger systems used to cool a whole dwelling. Since the higher the difference between indoor and outdoor temperatures, the less efficient an air conditioner tends to be, SEER is a more accurate reflection of typical energy efficiency of an air conditioner through a cooling season.

While there is not an exact conversion formula to go from CEER to SEER or vice versa, a general rule of thumb is that SEER can be obtained by multiplying CEER by about 1.2.

Doing your own research

To find more information on air conditioner ratings for ENERGY STAR qualified air conditioners, see:

• ENERGY STAR: Room air conditioners
• ENERGY STAR: Central air conditioners

Each of these provides a searchable database. Near the top right you can also find a link to a spreadsheet or CSV file which you can download and open in your favorite spreadsheet program. This makes it easy for you to filter and sort by BTU, ENERGY STAR qualified or not, CEER or CEER rating, or whatever other air conditioner ratings you care about. Happy searching, and remember to strive for the highest efficiency unit you can afford.