Why Does My Portable AC Have Two BTU Ratings?
Because two different tests produced them. The bigger number is usually the ASHRAE-128 laboratory rating — a test originally designed for window units. The smaller number is the DOE SACC (Seasonally Adjusted Cooling Capacity) rating, a portable-AC-specific test that factors in duct heat leakage, air infiltration, and cycling losses. For the same unit, SACC typically runs 15-50% lower than the advertised ASHRAE figure.
The one thing to know: A portable air conditioner sold as '14,000 BTU' is almost always reporting an ASHRAE-128 laboratory rating, not what it will actually deliver in your room. Since the DOE's 2017 test procedure and its 2023 update, manufacturers must also disclose a SACC (Seasonally Adjusted Cooling Capacity) rating, which factors in duct/hose heat leakage, infiltration of outside air, and cycling losses. The SACC number typically runs 15-50% lower than the advertised ASHRAE figure for the same unit — a '14,000 BTU' unit is commonly an 8,000-12,000 BTU SACC unit in practice. Neither number is 'fake'; they measure different things.
The two tests, side by side
| Test | What it measures | Typically bigger or smaller? |
|---|---|---|
| ASHRAE-128 | Cooling output under controlled lab conditions, originally designed for window/room AC units | Bigger (advertised) |
| DOE SACC | Cooling output adjusted for exhaust-duct heat leakage, infiltration of outside air, and cycling losses | Smaller (disclosed, real-world) |
Why the gap exists
A portable AC has to vent hot exhaust air outside through a hose, unlike a split system with a fully sealed refrigerant loop. That hose leaks some heat back into the room, and drawing air out through it pulls the room into negative pressure — outside air seeps back in through door gaps, window seals, and wall penetrations to replace what was exhausted. The ASHRAE-128 test doesn't account for any of that; the SACC test does. Add the compressor motor's own waste heat (which stays in the room, since the compressor sits inside the cabinet) and you get a real-world capacity meaningfully below the lab number.
Is this new?
The DOE issued the test-procedure final rule establishing SACC testing in 2016, with compliance applying starting the 2019 model year. It isn't new, but it also isn't universally enforced in how retailers list products — see Is SACC Disclosure Required? for what we found when we checked current listings.
How big is the gap in practice?
Across the current popular models in our SACC Reality Index, we found derived gaps ranging from about 14% to 50% between the advertised ASHRAE figure and the disclosed SACC figure for the same unit — see the full table with sources.
This page explains published rating terminology; it is not a performance guarantee for any specific unit or room.
Frequently Asked Questions
Because two different test procedures produced them. The ASHRAE-128 rating is a laboratory test originally built for window units and is usually the bigger number on the box. The DOE SACC (Seasonally Adjusted Cooling Capacity) rating is a newer, portable-AC-specific test that accounts for real-world duct heat leakage, air infiltration, and cycling losses — so it's typically 15-50% lower for the same unit.
The SACC number. It's designed specifically to reflect what the unit will deliver once it's hooked up with its exhaust hose in a real room, not a sealed lab chamber. The ASHRAE number will make every unit look like it covers a bigger room than it actually will.
The DOE issued its test-procedure final rule in 2016, and compliance with SACC-based labeling applies starting with the 2019 model year. Since then, portable AC packaging and major retail listings are required to show the SACC figure alongside the ASHRAE figure — though we still find budget listings that omit it.
No. Both figures come from legitimate, DOE-recognized test methods measuring different things. A wider gap usually reflects hose configuration (single vs. dual hose) or compressor design, not misrepresentation. See our derived, source-cited comparison in the SACC Reality Index.