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What size portable air conditioner do you need?
Updated
Enter your room. The calculator uses the ENERGY STAR sizing chart and its adjustments, then tells you the SACC rating to look for. Match it against the SACC or DOE number on the listing, not the bigger number on the box.
Portable AC size calculator (SACC BTU)
An estimate. It uses the ENERGY STAR room AC sizing chart and its sun, people and kitchen adjustments. The ceiling step is ours: past 8 ft we scale up by height divided by 8. Compare the result with the SACC or DOE number on a portable listing, not the bigger ASHRAE number.
Why the answer is a SACC number
ENERGY STAR's chart was written for room air conditioners, the kind that sit in a window with the hot side outdoors. A portable sits indoors. The DOE test for portables, called SACC, measures what reaches the room after heat from the hose and the air that leaks in are counted. That makes SACC the closer match to the chart. The ASHRAE number on the box leaves those losses out. More on the ASHRAE vs SACC page.
Worked examples
| Room | SACC to look for | Picks with enough SACC |
|---|---|---|
| 12 x 14 ft bedroom (168 sq ft), normal sun | 6,000 | Midea Duo 12,000 BTU, Whynter ARC-14S, BLACK+DECKER BPACT14WT and Whynter ARC-122DS |
| Same bedroom, very sunny | 7,000 | Midea Duo 12,000 BTU, Whynter ARC-14S, BLACK+DECKER BPACT14WT and Whynter ARC-122DS |
| 200 sq ft room with 10 ft ceilings | 7,500 | Midea Duo 12,000 BTU, Whynter ARC-14S and BLACK+DECKER BPACT14WT |
| 16 x 20 ft living room (320 sq ft), very sunny, three people | 9,500 | Midea Duo 12,000 BTU, Whynter ARC-14S and BLACK+DECKER BPACT14WT |
| 400 sq ft kitchen | 13,000 | none of the picks here |
Take the 12 x 14 bedroom. The ENERGY STAR chart gives 6,000 BTU for 150 up to 250 sq ft. Very sunny adds 10 percent, so 6,000 x 1.1 = 6,600, rounded up to 7,000. A 10,000 BTU box can fall short of that. The BLACK+DECKER BPACT10WT has 10,000 on the box and 5,550 DOE.
- Bedroom normal sun6,000 BTU SACC
- Bedroom very sunny7,000 BTU SACC
- 200 sq ft at 10 ft ceiling7,500 BTU SACC
- Sunny living room with 3 people9,500 BTU SACC
- 400 sq ft kitchen13,000 BTU SACC
The adjustments, and where they come from
- Room size: the ENERGY STAR chart. Measure length times width in feet. It assumes an 8 ft ceiling.
- Sun: ENERGY STAR says cut capacity by 10 percent for a heavily shaded room and add 10 percent for a very sunny one.
- People: add 600 BTU for each person past two who is usually in the room.
- Kitchen: add 4,000 BTU.
- Ceiling: ENERGY STAR notes that the chart assumes 8 ft ceilings and suggests more capacity for higher ones. It gives no number. We scale up by ceiling height divided by 8. That step is our estimate.
When no portable is big enough
The highest SACC on this site is 10,200 BTU, which fits about 450 sq ft on the chart. For an open floor plan or a big sunny room past that, one portable will run flat out and still lose ground. Cool the room you use most with the door shut, use two units, or look at a window unit.
Size your own room with the SACC calculator, or compare all seven picks on the roundup page.