BTU vs SACC: why the box says 14,000 and the label says 9,500

Go to a portable air conditioner listing and you will often find two capacity figures within a few lines of each other. A Whynter ARC-14S is sold as a 14,000 BTU unit, and its own specification page states 9,500 BTU SACC. A Midea Duo MAP14S1TBL is also sold as 14,000 BTU, and Midea states 12,000 BTU SACC.

Same headline number. A 2,500 BTU difference in what actually reaches the room. If you sized a room from the box, you would think you were choosing between two equivalent machines.

A portable air conditioner has a problem a window unit does not. A window unit sits in the wall of the room: cold side in, hot side out, and the heat it rejects lands outside. A portable sits inside the room and pushes its waste heat out through a duct. Two things follow, and the DOE test procedure is built to capture both.

First, the duct is hot and it is in your room. A flexible hose full of exhaust air runs across the floor, radiating heat back into the space the machine is trying to cool. Some of the cooling is spent on the duct.

Second, and much worse for single-hose units: air leaves the room and something has to replace it. A single-hose portable draws the air it needs to cool its condenser from the room, then blows that air outside. The room is now at slightly negative pressure, so outside air — the hot air you are trying to escape — infiltrates through gaps around doors, windows and floors to make up the difference. You are, in effect, paying to pull the outdoors in.

The DOE test procedure at 10 CFR part 430, subpart B, appendix CC subtracts both effects from the measured cooling capacity to give adjusted cooling capacity (ACC), then takes a weighted average of ACC measured at two representative operating conditions to give SACC. That procedure has been in force since 1 June 2016.

The number on the box, by contrast, typically comes from ASHRAE Standard 128, which measures cooling capacity without accounting for duct losses or infiltration at all. Whynter labels its two figures exactly that way on its own page: “14,000 BTU (ASHRAE-128 Standard)” and “9,500 BTU (DOE 2017 Standard)”.

A note on what we are not telling you. The precise weighting factors and test temperatures inside that weighted average are specified in appendix CC, and we could not confirm them against the primary regulation text when writing this page — two secondary sources gave conflicting figures. So we have described the mechanism and cited the standard, and we are publishing no weighting number. You do not need it to make the decision below, and a number we cannot verify is worth less than an honest gap.

This is the part almost nobody publishes: the haircut is not a fixed ratio. It depends on how the machine is built. Both rows below are the manufacturer’s own published pair of numbers, not our estimate.

Two units, same headline capacity, and one delivers 26% more cooling than the other by their own published figures. If a reviewer ranks “14,000 BTU portables” and never mentions SACC, they have put two materially different machines in the same bucket.

And note that both of those are dual-hose units — the better configuration. Single-hose units carry the full infiltration penalty on top of duct losses.

SACC. Always SACC. Run the ENERGY STAR sizing table against the SACC figure, not the box figure:

Do the substitution for the ARC-14S. Its SACC is 9,500 BTU, which sits between the table’s 9,000 BTU row (350–400 sq ft) and its 10,000 BTU row (400–450 sq ft). So it is honestly a roughly 400 square foot machine.

Whynter’s own product page claims coverage of 500 sq ft.

Those two published numbers do not agree, and the gap between them is exactly the SACC haircut being quietly left out of the coverage claim. We are not accusing anyone of lying: 14,000 BTU under ASHRAE-128 would indeed serve about 550 sq ft on that table. But 14,000 BTU is not what arrives in your room, and the same page says so 20 lines further down.

For window air conditioners you can sidestep marketing entirely and read the certified data: ENERGY STAR publishes tested CEER and modeled annual kWh for every certified unit, and our window AC rankings are built on it.

No such program exists for portable air conditioners. The ENERGY STAR certified room air conditioner dataset returns window and through-the-wall units only; a portable AC cannot carry an ENERGY STAR label because there is no specification for it to meet. Portables are covered by the DOE test procedure — which is what gives you SACC — but there is no efficiency certification on top.

That absence is itself a buying signal, and it is one reason a window unit beats a portable whenever a window unit will physically fit.

1. Look for two capacity numbers. If a listing shows only one, it is almost certainly the ASHRAE figure. Find the spec sheet or the EnergyGuide label.
2. Count the hoses. One hose means the infiltration penalty applies in full. Two means the condenser draws its air from outside and the penalty is much smaller.
3. Take the SACC figure to the sizing table and read off the room area it honestly serves.
4. Compare that with the coverage claim in the listing. If the listing claims meaningfully more, you now know why.
5. Then check what it costs to run — the ARC-14S draws 1,300 W, and we work that through to a monthly figure here.

If, having done that, the honest SACC figure is too small for your room, the answer is not a bigger portable. It is a window unit, where the capacity on the label is the capacity in the room.