ASHRAE vs DOE SACC: why your portable AC lists two BTU numbers
ASHRAE vs DOE SACC is the fine print that explains why a “14,000 BTU” portable AC can feel weaker than an 8,000 BTU window unit. Both numbers are honest measurements — they just measure different things, and only one of them predicts what reaches your skin.
What the ASHRAE number measures
The ASHRAE rating measures raw cooling capacity at the machine under favourable lab conditions. It ignores what happens next in a real room: a single-hose portable expels air outdoors, which pulls warm outdoor air back in through every gap, and its hot exhaust hose radiates heat along its whole length inside your room.
What DOE SACC fixes
The US Department of Energy’s Seasonally Adjusted Cooling Capacity weights performance across realistic conditions and subtracts those self-inflicted losses. That is why the SACC figure is always smaller — commonly 55–75% of the ASHRAE figure on single-hose designs — and why dual-hose units keep more of their rating.
How to use this when buying
- Size your room with our BTU calculator, which outputs both scales.
- Compare models on SACC only; treat ASHRAE-only listings as a transparency red flag.
- Remember neither number applies to evaporative devices — those live in a different physics entirely.
One rating tells you what the compressor can do in a lab; the other tells you what your room will actually receive. Buy on the second.
Frequently asked questions
Which number should I size with?
The DOE SACC figure. It accounts for the heat a single-hose portable leaks back into the room, so it predicts delivered cooling far better than the ASHRAE lab number.
How do the two roughly convert?
On typical single-hose portables the DOE SACC rating lands around 55–75% of the ASHRAE number. A “14,000 BTU” ASHRAE unit often delivers roughly 8,000–10,000 BTU SACC.
Do evaporative coolers have BTU ratings?
Not meaningful ones. BTU ratings describe heat removal by refrigeration. Evaporative and personal coolers are compared by airflow and temperature drop instead — a different physics, covered in our evaporative guide.
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