The Cooling Numbers
This is Chill Factor Lab's normalized reference dataset for home cooling — the honest BTU-per-room-size math, the 2017 DOE rule that split portable-AC ratings into ASHRAE (bigger, less real) and SACC (smaller, real-world), the CEER/SEER/EER decoder, single-vs-dual-hose efficiency, fan CFM/dB classes, and the humidity ceiling on evaporative cooling. It is a reference dataset, not a buying guide — pair it with a specific product's published spec sheet before you buy.
The one thing to know: Since a 2017 DOE rule, portable air conditioners must also list a SACC (Seasonally Adjusted Cooling Capacity) rating alongside the older ASHRAE BTU number — and SACC is typically 25–45% lower for the same unit, because it's tested closer to real operating conditions (83°F/95°F) instead of ASHRAE's ideal 80°F lab test. A portable AC box printed '14,000 BTU' is very often a genuinely smaller ~8,000–9,000 SACC-rated machine. Always size a portable AC off the SACC number, never the bigger ASHRAE number on the front of the box.
BTU-per-room-size table
| Room size | Baseline BTU | Typical room |
|---|---|---|
| 100–150 sq ft | 5,000–6,000 | Small bedroom, dorm, home office |
| 150–250 sq ft | 6,000–7,000 | Standard bedroom |
| 250–350 sq ft | 7,000–8,500 | Large bedroom, small living room |
| 350–450 sq ft | 8,500–10,000 | Mid-size living room |
| 450–550 sq ft | 10,000–12,000 | Large living room, open studio |
| 550–700 sq ft | 12,000–14,000 | Small open-concept apartment |
| 700–1,000 sq ft | 14,000–18,000 | Large open floor, small house zone |
Baseline assumes 8-ft ceilings, average insulation, average sun exposure, two occupants. Adjust using the table below.
Sizing adjustments
| Condition | Adjustment |
|---|---|
| Kitchen adjoins or is part of the room | +4,000 BTU |
| Room gets heavy direct sun most of the day | +10% of base BTU |
| Room is heavily shaded all day | −10% of base BTU |
| Each occupant beyond the first two | +600 BTU per person |
| Ceiling height above 8 feet | +1,000 BTU per additional foot |
SACC vs ASHRAE: the 2017 DOE portable-AC rating gap
Since October 1, 2017, the DOE has required portable air conditioners to disclose a SACC (Seasonally Adjusted Cooling Capacity) rating, tested at 83°F and 95°F, alongside the older ASHRAE rating tested at an ideal 80°F. SACC also factors in real installation losses. The result: SACC typically runs 25–45% below the ASHRAE number for the same physical unit, and single-hose units see the larger gap within that range. Manufacturers are required to disclose SACC, but the bigger ASHRAE figure is still what's printed largest on the box.
| ASHRAE BTU (box number) | Typical SACC (real-world) | Effective class |
|---|---|---|
| 8,000 BTU (ASHRAE) | ≈4,500–5,500 SACC | Small-room class once corrected |
| 10,000 BTU (ASHRAE) | ≈5,500–6,500 SACC | Common single-hose 'bedroom' unit |
| 12,000 BTU (ASHRAE) | ≈7,000–8,000 SACC | Popular mid-size portable class |
| 14,000 BTU (ASHRAE) | ≈8,000–9,500 SACC | The most-marketed 'big number' size |
Always size a portable AC off the SACC figure, and compare SACC-to-SACC across models — comparing one model's ASHRAE number to another's SACC number is an apples-to-oranges mistake.
Single-hose vs dual-hose efficiency
| Configuration | Pressure effect | Real-world loss | Setup |
|---|---|---|---|
| Single-hose | Negative (room air exhausted out) | ≈15–30% effective cooling loss vs rated capacity | One hose, one window-kit panel |
| Dual-hose | Neutral (intake drawn from outside) | Minimal — closest to rated capacity | Two hoses or a wider two-port window kit |
CEER / SEER / EER decoder
| Rating | Covers | How it's measured | Note |
|---|---|---|---|
| EER | Room/window AC (older DOE standard, pre-2014) | BTU output ÷ watts input, single test point | Mostly superseded by CEER for window units |
| CEER | Window & portable AC (current DOE standard since 2014) | Like EER but also counts standby power draw | Roughly 8–15 for current units; higher = more efficient |
| SEER / SEER2 | Central & split-system (mini-split) AC | Seasonal cooling output ÷ seasonal energy input | NOT used for window/portable units at all |
Fan CFM & dB classes
Fans have no "cooling capacity" rating — CFM (airflow) and dB (noise) are the only meaningful specs, since a fan cools people via wind-chill, not the room's air temperature.
| Fan type | Typical CFM (high) | Typical dB (high) | Best fit |
|---|---|---|---|
| Box fan | ≈2,000–3,000+ on high | ≈55–70 dB on high | Best CFM per dollar; loud on high |
| Tower fan | ≈400–700 | ≈45–58 dB | Slim footprint, quieter, less raw airflow |
| Pedestal fan | ≈1,000–1,500 | ≈50–62 dB | Adjustable height, aims airflow at head level |
| High-velocity floor fan | ≈3,000+ | ≈65–70 dB | Garage/workshop class, not for bedrooms |
Evaporative cooler effectiveness by humidity
| Relative humidity | Typical temp drop | Verdict |
|---|---|---|
| Under 30% RH | ≈20–30°F | Excellent — evaporative cooling's ideal zone |
| 30–50% RH | ≈10–20°F | Still meaningfully effective |
| 50–60% RH | ≈5–10°F | Marginal — barely worth running |
| Above 60% RH | Little to none | Not effective — adds humidity for no real cooling |
Caveats — read before citing a number
- BTU sizing is a starting estimate, not an engineering calculation — a room with unusual insulation, altitude, or airflow will vary from the table.
- SACC ranges are typical, not universal — always check the specific model's disclosed SACC rating rather than assuming the midpoint of our range.
- CFM and dB figures for fans are manufacturer-published ranges for representative models in each format, not a physical law — individual models vary.
- Evaporative-cooler temperature drops are climate figures, not guarantees — actual performance depends on outdoor temperature, airflow, and unit condition too, not humidity alone.
- This page reports appliance specs and DOE rating rules, not a safety determination for any specific heat event — see a doctor's or public-health guidance for heat-illness concerns.
Methodology & versioning
Version 1.0 — published July 30, 2026. Facts are drawn from the DOE's 2017 portable-AC labeling rule and SACC/ASHRAE test-condition documentation, DOE CEER/EER rulemaking for room air conditioners, manufacturer-published spec sheets for representative fan and evaporative-cooler models, and public HVAC-industry reference material on evaporative-cooling humidity performance, cross-checked against our existing guides. We do not lab-test appliances ourselves; this is a specifications-facts reference, not a lab result. Corrections: if a rating rule or typical range changes, this page and the CSV below are updated in place and the version/date bumped — see How We Evaluate for our full editorial policy.
Machine-readable download: the full table is available as CSV at /cooling-numbers.csv, and a condensed digest is maintained in /llms-full.txt.
This page is general reference information about appliance specifications and DOE rating rules, not a safety determination for your specific room, climate, or health situation.
Frequently Asked Questions
Chill Factor Lab's normalized reference dataset for home cooling — BTU-per-room-size sizing, the SACC-vs-ASHRAE BTU gap on portable ACs, the CEER/SEER/EER rating distinction, single-vs-dual-hose efficiency loss, fan CFM/dB classes by format, and the evaporative-cooler humidity ceiling — all in one versioned, citable table.
ASHRAE tests at an ideal 80°F; the DOE's 2017-mandated SACC rating tests at 83°F and 95°F, closer to real summer conditions, and factors in duct/hose losses. The result is a rating that's typically 25–45% lower for the same physical unit. Manufacturers still print the larger ASHRAE number more prominently because it's the bigger number, not because it's the more useful one for sizing.
No. Window and portable units are rated in CEER by the DOE; SEER is a seasonal rating used for central and split-system AC and does not apply to window/portable units at all, regardless of how a listing describes it.
It means more airflow, which increases the wind-chill effect on skin — but a fan never changes the room's actual air temperature. A very high-CFM fan in an empty room does nothing; the airflow only helps a body that's present to feel the evaporative cooling effect.
Effectiveness declines steadily above roughly 50–60% relative humidity, and above that it mostly just adds moisture to the air rather than cooling it meaningfully. Below 30% RH, the same technology can drop room temperature 20–30°F — the difference is entirely climate, not the unit's build quality.