# Portable AC BTU: ASHRAE vs DOE Explained

_Last updated: 2026-09-26_

## Short answer

A portable AC has two BTU figures because they use different tests. ASHRAE is the older, higher number; DOE is measured under more realistic conditions and is usually much lower. Size with the DOE number, and never compare an ASHRAE figure to a DOE figure.

## What the two numbers mean

- ASHRAE 128: an older test that measured cooling capacity under ideal conditions, so it reads high.
- DOE (10 CFR 430): the current test introduced in 2017, which accounts for the heat a single-hose portable AC pulls back in, so it reads lower.
- Many listings still show both, which is why the same unit appears as, say, 11,000 BTU ASHRAE and 7,200 BTU DOE.

## How to size a room

- Use the DOE number and a rough 20 BTU per ft² for average conditions.
- Add capacity for a sunny room, a top-floor room, a kitchen, or more than two occupants.
- Reduce it if the room is shaded and well insulated.
- Match the exhaust setup: a leaking window kit wastes capacity no matter the rating.

## Worked examples

- A 250 ft² bedroom: about 5,000 DOE BTU for average conditions.
- A sunny 350 ft² living room: about 7,000–8,000 DOE BTU.
- A 150 ft² bedroom: about 3,000–4,000 DOE BTU.

## Common mistakes

- Comparing an ASHRAE rating to a DOE rating and picking the "bigger" unit.
- Buying by BTU alone while ignoring a leaking window kit.
- Expecting a portable AC to match a window or split unit of the same nominal capacity.
- Ignoring the noise rating, since bigger units are usually louder.

## Sources

U.S. Department of Energy, 10 CFR 430 test procedure for portable air conditioners; AHRI standards for the older ASHRAE-based rating.

## Frequently asked questions

**Q: Which BTU number should I use to compare portable ACs?**

A: Use the DOE number (sometimes shown as SACC). Compare DOE to DOE across models; the ASHRAE number will make any unit look larger than it performs.

**Q: Why is the DOE number so much lower?**

A: The DOE test reflects real use, including the warm air a single-hose unit draws back into the room, so the measured cooling is lower than the ideal-condition ASHRAE figure.

**Q: Is a dual-hose unit worth the extra cost?**

A: Usually for larger rooms. A dual-hose unit avoids pulling in already-cooled room air, so it uses its capacity more effectively than a single-hose unit of the same rating.

## Recommended options

These listings show DOE capacity. Match that number to your room size and seal the window kit to get the rated cooling.

- [DREO 543S Portable Air Conditioner](https://www.amazon.com/dp/B0H7BMR888?maas=maas_adg_api_585602613512925350_static_12_201&ref_=aa_maas&tag=maas&aa_campaignid=PBd80bd4ce4ece40f44bcc76fcc0c48425&aa_adgroupid=1709F0YoFvn8WQ063L58iFizKDKVpa2b3GHOYuFXiqmLN1RXz8YT3n9by2hV4_a1UOj3lhrTxeHQ0tffeqQbC&aa_creativeid=4c49c7_agox8Dnfln5YFpaffCTsBTExy8Meqw7K_aH3G3MyZo_c) — DREO, rating 4.2/5 (1334 reviews)
- [DREO 516S Portable Air Conditioner](https://www.amazon.com/dp/B0GQGJ6DML?maas=maas_adg_api_585602613512925350_static_12_201&ref_=aa_maas&tag=maas&aa_campaignid=PBd80bd4ce4ece40f44bcc76fcc0c48425&aa_adgroupid=4fb2VYJ6Pwk9zor9pIsuXQFhc0usX44qjhak8BA_a0_bCEu3kAnU_a6FSgwfcH0Hr_bCukAi2CeaMaSoi7gRCJFg&aa_creativeid=9893bt31K2W7fp7u8SAKOBcsuXVYwVj2pwaK5tGNu8S5MIQ_c) — DREO, rating 4.1/5 (746 reviews)

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