This article is about portable air conditioners and how to know what size you need for the room you want to cool in your home or business.
SACC vs ASHRAE – Know What the Numbers Mean
Portable air conditioners are unique in that they are rated by two different agencies for the number of BTUs of heat they can move every hour.
When you look for a portable air conditioner, you might see that there are two separate sets of numbers on the box that are both “BTU”. For example, one might say “10,000 BTU/h ASHRAE Standard”, and the other one might say, “7,000 BTU/h U.S. DOE Standard”. These numbers are the results of two different methods of testing that were done to determine how efficient the unit was.
Shopping tip: If the box or product page online lists only one BTU number for a portable air conditioner, then it is the new SACC rating from the US Department of Energy, and it’s the correct one to consider when choosing the right size portable air conditioner for your room.
Info Tip: Without going into a lot of detail, the DOE Standard is the one that you should use when purchasing a portable air conditioner because it specifically applies to portable air conditioners and no other AC type. It might also have the letters, “SACC” (Seasonally Adjusted Cooling Capacity) alongside it.
Why Two Numbers? Why is SACC Less than ASHRAE?
The reason why there are two sets of numbers – and why you need to go by the U.S. DOE Standard – is because portable air conditioners simply will not cool as efficiently as other types of AC units, such as window AC’s or central AC’s.
This is because of three reasons: (1) some of the room air that has been cooled by the portable AC is used for cooling its internal parts, (2) hot air being blown out the exhaust hose creates a negative pressure in the room which pulls warm air from other areas back into the room, and (3) the exhaust hose gets hot, and some of that heat is radiated back into the room you are trying to cool.
The Third Number – Room Size
Usually there is a third number on the box that tells you how many square feet the portable will cool. This is a very important number and might even be called “the bottom line”, since what you really want in a portable air conditioner is one that will cool the room of your choice.
Portable Air Conditioner BTU and Room Size Calculators
There are two handy calculators that you can use to help in making this decision. They do the reverse of one another, which you’ll see as you use them.
1. The first calculator answers the question “What size AC do I need for a room this size?” It is the right question if you do not have an AC and are shopping for one.
2. The second calculator answers the question, “What room size will this AC cool?” It’s the right question if you already have a portable air conditioner and want to know how big a room it will serve.
1. Calculator to Convert Room Size to BTU
Convert Room Size to BTU
To use this first calculator, simply type in (or select with the arrows) the size of the room you want to cool in the box, and the Recommend Portable AC Unit Size will appear below the box.
2. Calculator to Convert BTU to Room Size
Convert BTU to Room Size
To use this second calculator, type in (or select with the arrows) the DOE/SACC rating of a portable air conditioner, and the Portable AC Cooling Room Size will appear below the box.
BTU and Room Size Chart
We’ve done the math for you as well. This chart shows common room air conditioner sizes in the left column. Note that SACC/DOE ratings are used. So, this is ideal for portable air conditioners.
The right column shows the room size. We could say “Up to” before all the room sizes. Or you can consider the room size to be the maximum room size under normal conditions (average ceiling height, average insulation, average summer temperature outdoors, etc.).
| Portable AC Size | Room Size |
| 5000 BTU DOE (SACC) | 150 sq ft |
| 5500 BTU DOE (SACC) | 200 sq ft |
| 6000 BTU DOE (SACC) | 250 sq ft |
| 7000 BTU DOE (SACC) | 280 sq ft |
| 7500 BTU DOE (SACC) | 320 sq ft |
| 8000 BTU DOE (SACC) | 350 sq ft |
| 9000 BTU DOE (SACC) | 400 sq ft |
| 10000 BTU DOE (SACC) | 450 sq ft |
| 12000 BTU DOE (SACC) | 550 sq ft |
Convert ASHRAE to SACC
If you have an older portable air conditioner and it doesn’t list the new SACC ratings, this table makes the conversion for you.
Then you’ll have an idea of the SACC ratings, and you can use the chart above or the calculators to determine the size of the room it will cool.
Here is a chart to help you to compare the ASHRAE to the U.S. DOE Standard/SACC ratings for portable air conditioners.
| ASHRAE (BTU) | SACC (BTU DOE) | Room Size |
| 8,000 | 4,000 – 6,000 | 125 – 250 Sq Ft |
| 8,500 | 5,000 – 6,000 | 150 – 250 Sq Ft |
| 10,000 | 6,000 – 7,000 | 250 – 300 Sq Ft |
| 11,000 | 7,000 – 8,000 | 300 – 350 Sq Ft |
| 12,000 | 7,000 – 10,000 | 300 – 450 Sq Ft |
| 13,000 | 8,000 – 10,000 | 350 – 450 Sq Ft |
| 13,500 | 9,000 – 10,000 | 400 – 450 Sq Ft |
| 14,000 | 9,000 – 12,000 | 400 – 550 Sq Ft |
| 15,000 | 10,000 – 12,000 | 450 – 550 Sq Ft |
Looking at this chart, you can see that the efficiency rating for portable air conditioners (DOE/SACC) is between 30-50% lower than the ASHRAE rating. As mentioned above, this is because of the various ways that some of the cooled air is lost and some warm air comes back into the room being cooled. As the chart shows, a portable rated at 5500 btu doe, for example, will cool a room of approximately 200 square feet. Another portable rated at 10000 BTU DOE will cool a room of approximately 450 square feet.
What is the highest BTU DOE for portable ac?
The portable air conditioner with the highest BTU DOE rating we could find came in at 10,800 BTU DOE/SACC. This was said to be able to cool 600 square feet of space and remove 100 pints of moisture from the air per day.
What is the lowest BTU DOE for portable ac?
The portable air conditioner with the lowest BTU DOE rating we could find produced 4,000 BTU DOE/SACC. It was designed to cool 225 square feet of space. The smallest unit most manufacturers make is a 5,000 BTU DOE model that is said to cool a room of about 150 square feet.
The Final Thought to Remember
Portable air conditioners are quite popular, and are more pleasing to the eye than many window air conditioners. But because of their design and how they operate, portable air conditioners are less efficient than window AC’s. If you decide to purchase one, just be sure to check to see what the DOE/SACC rating is. This is the number that will tell you how much space it will effectively cool.
