HVAC Calculators
SACC vs ASHRAE BTU: Why Portable AC Ratings Dropped
The ASHRAE (or "ASHRAE 128") number on a portable AC is its older, single-condition test capacity. SACC, the Seasonally Adjusted Cooling Capacity required by the US Department of Energy, subtracts heat that leaks back from the unit's own hose and case and warm air drawn in through gaps, so it is typically 30–50% lower. Compare and size portable units by SACC.
Two numbers on one box
Shop for a portable air conditioner and you will often see something like "14,000 BTU (ASHRAE) / 9,500 BTU (SACC)" on the same carton. Both numbers are measured in BTU per hour, and both come from standardized lab tests. They differ because they answer different questions:
- ASHRAE rating: how much heat the refrigeration system moves under one fixed test condition, with little allowance for what happens in a real room.
- SACC: how much useful cooling actually reaches the room over a typical season, after subtracting the unit's self-inflicted losses.
The US Department of Energy adopted a dedicated portable AC test procedure in the mid-2010s, and SACC became the figure manufacturers must use for federal ratings from 2017 onward. Many brands still print the older figure because it is bigger, sometimes labelled ASHRAE 128 or simply "BTU".
Where the lost capacity goes
A window air conditioner keeps its hot condenser outside, so nearly all the heat it pulls from the room leaves the building. A portable unit keeps everything indoors and relies on a hose to carry condenser heat out. That creates three losses that the old test largely ignored:
- Hot exhaust hose. The duct carrying condenser air can run well above 100 °F, and it radiates part of that heat back into the room.
- Warm cabinet. The compressor and condenser are inside the case, and some of their heat escapes through the casing.
- Infiltration (single-hose units). A single-hose unit blows room air outside to cool its condenser. That air is replaced by warm, humid outdoor air drawn in under doors, through windows and through leaks. On a hot day this can cancel a large share of the cooling.
The DOE test captures these effects and weights results across two outdoor conditions (a very hot 95 °F day and a more typical 83 °F day), producing the seasonally adjusted figure.
Typical ASHRAE vs SACC values
The gap varies by model and is larger for single-hose units. Typical pairings seen on the market:
| ASHRAE label | Typical SACC, single-hose | Typical SACC, dual-hose | Room it really suits |
|---|---|---|---|
| 8,000 BTU/h | 4,000–5,000 | 5,000–6,000 | Up to about 200 sq ft |
| 10,000 BTU/h | 5,000–6,500 | 6,000–7,000 | About 200–300 sq ft |
| 12,000 BTU/h | 6,000–8,000 | 7,500–9,000 | About 250–400 sq ft |
| 14,000 BTU/h | 7,500–10,000 | 9,000–10,500 | About 350–500 sq ft |
These ranges are approximate. Use the SACC on the specific model's spec sheet or EnergyGuide-style label.
The room-size claims printed on many boxes are based on the larger ASHRAE number. If a box says "cools up to 550 sq ft" next to a 14,000 BTU ASHRAE rating, size by the SACC instead and expect closer to 400 sq ft in average conditions.
How to size a portable AC with SACC
Use the same room-load method as for any air conditioner, then pick a portable unit whose SACC meets or exceeds the load:
Room load ≈ Area × 20 × Sun adjustment + 600 per person over two + 4,000 for a kitchen
Choose: SACC ≥ Room load
Example: a 300 sq ft bedroom with average sun and two people needs about 6,000 BTU/h. A unit labelled 10,000 BTU ASHRAE / 5,800 BTU SACC is borderline; one labelled 12,000 ASHRAE / 7,000 SACC is the safer choice. Run your own room through the room BTU calculator, and see the AC tonnage calculator if you are comparing against a central system.
Single-hose vs dual-hose
A dual-hose unit draws outdoor air through one hose to cool its condenser and sends it back out through the other. The room is not depressurized, so there is much less infiltration, and its SACC sits closer to its ASHRAE number. On very hot, humid days the difference in real comfort is noticeable.
- Insulate the exhaust hose with a fabric sleeve to reduce radiated heat.
- Keep the hose as short and straight as the instructions allow; every extra foot adds heat back to the room.
- Seal the window kit carefully with foam strips; gaps let hot air flow straight back in.
For installs without a standard sash window, see how to vent a portable AC without a window, and for condensate handling, how to drain a portable AC.
When a portable unit is the wrong tool
Even rated by SACC, a portable air conditioner is the least efficient common way to cool a room. If the window allows it, a window unit of the same nominal size delivers more cooling for less electricity, and a ductless mini-split delivers more again. Portables make sense for renters who cannot fit a window unit, for rooms with casement or sliding windows, and for temporary or seasonal needs. For a room larger than about 500 sq ft or one with heavy sun, a portable usually struggles whatever the number on the box; the mini-split sizing calculator is a better starting point there.
Efficiency labels: CEER and what to compare
The DOE also rates portable units by CEER (combined energy efficiency ratio), which uses SACC and includes standby power. Higher is better. A federal minimum efficiency standard for portable air conditioners took effect in 2025, so new units have to meet a floor based on their SACC. Window units are rated under a different procedure and a separate CEER standard, and their capacities are not reduced the same way because the hot side is already outdoors. That is one reason a window unit almost always out-cools a portable with the same label number. For running costs at your electricity rate, see the cost to run an air conditioner.
Frequently asked questions
Is SACC or ASHRAE more accurate?
SACC is the better guide to real cooling in a room, because it includes the heat and air leakage the unit causes. The ASHRAE figure overstates what a portable unit delivers.
Why is my 14,000 BTU portable AC not cooling the room?
If 14,000 is the ASHRAE figure, its real seasonal capacity may be closer to 8,000–10,000 BTU/h. Check the SACC on the spec sheet, insulate the hose, seal the window kit and consider a dual-hose or window unit for large or sunny rooms.
Do window air conditioners have a SACC rating?
No. SACC applies to portable units. Window and through-wall units have a single cooling capacity under their own DOE test, which already reflects the condenser being outside.
Last reviewed 2026-10-28