Ratings decoder
The Two BTU Numbers on One Portable AC Box
The number in the product name and the number in the specifications describe the same machine. They can differ by a third or more.
The same thing, read twice — DREO 515S Portable AC, 12,000 BTU ASHRAE
What the ASHRAE figure says
12,000 BTU. That is the headline number, it appears in the product name, and it comes from a test method that does not account for everything a portable unit does in a real room.
What the DOE / SACC figure says
8,000 BTU. Same machine, measured by the Department of Energy procedure, which accounts for heat the unit brings back into the room and averages across specified conditions.
Both readings come from the listing for DREO 515S Portable AC, 12,000 BTU ASHRAE, which states: listing states 8,000 BTU DOE, drainage-free cooling, fan and dehumidifier modes, app and voice control.
What is actually going on
A portable air conditioner is the only appliance in this catalog that is routinely sold under two different capacity numbers at the same time, on the same box, both of them accurate to their own test method.
The larger figure comes from an ASHRAE test procedure and is the one that ends up in the product name, because it is the bigger of the two. The smaller figure is the Seasonally Adjusted Cooling Capacity, produced under the Department of Energy test procedure. SACC accounts for things the older method does not, including the heat a single-hose unit pulls back into the room by drawing indoor air through the machine and pushing it out of the window.
The spread is not small. Across the five vented units in this catalog the SACC figure runs between roughly 59 and 86 percent of the ASHRAE figure, depending on the machine. One of them is listed as 9,000 BTU with a stated SACC of 5,300. Another is listed as 8,500 with a stated SACC of 5,000.
Which one sizes a room? The SACC figure. It is the one produced by the procedure written for this appliance category, and it is the one that will not flatter a machine into a room it cannot handle. Where a listing also states a square footage, treat it as a seller figure about the product rather than a calculation about your room — none of them know your ceiling height, your insulation, how many people are in the room, or what the sun does to the west wall in the afternoon.
One consequence worth stating plainly: a machine whose two numbers sit close together is being described more conservatively than one where they are far apart. That is a fact about the listing, not a verdict on the hardware, but it is the kind of thing worth noticing while comparing boxes.
Lined up against each other
| Unit in this catalog | ASHRAE and SACC as stated | SACC as a share of the headline figure |
|---|---|---|
| Midea Duo Portable AC | 14,000 BTU headline, 12,000 BTU SACC stated. | About 86 percent — the narrowest gap in this catalog. |
| DREO 515S Portable AC | 12,000 BTU ASHRAE, 8,000 BTU DOE stated. | About 67 percent, with both figures stated in the listing. |
| Shinco Portable AC | 12,000 BTU headline, 7,500 BTU SACC stated. | About 63 percent, from the same headline figure as the DREO. |
| BLACK+DECKER Portable AC | 9,000 BTU headline, 5,300 BTU SACC stated. | About 59 percent — the widest gap here. |
| Midea Portable AC 8,500 | 8,500 BTU ASHRAE, 5,000 BTU SACC stated. | About 59 percent, on the smallest vented unit in the catalog. |
What this scale does not tell you
- Anything about your particular room. Ceiling height, insulation, sun exposure, occupancy and equipment heat are all outside both figures.
- Whether a window in the room can take the exhaust hose, which decides whether a portable unit is viable at all.
- How an evaporative cooler compares, because that machine publishes no BTU figure and is not doing the same job.
- How the unit performs at conditions outside the test procedure, which is what a seasonal average smooths over.