Window AC and Mini-Split BTU by Room, Adjusted for Climate
The chart on the box
Window units and mini-split heads are sold against the same 20 BTU per square foot assumption: 5,000 BTU for 150 sq ft, 8,000 for 350. That fits the middle of the country and misses both ends.
Climate-adjusted BTU per square foot
Dividing each city's whole-house load by floor area gives a per-square-foot figure for that climate. Across 3,206 cities the median is 15.7 BTU/hr per sq ft, ranging from 7.9 in San Francisco, CA to 30.4 in Bullhead City, AZ.
| City | 150 sq ft bedroom | 350 sq ft living room | 600 sq ft open plan kitchen and family room |
|---|---|---|---|
| San Francisco, CA | 1,200 | 2,800 | 4,700 |
| Lexington-Fayette urban county, KY | 2,400 | 5,500 | 9,400 |
| Bullhead City, AZ | 4,600 | 10,600 | 18,200 |
Adjust for the room
Add about 10% for a room with big west or south windows, and 600 BTU for each person beyond two who uses it regularly. Kitchens add about 4,000 BTU for the stove. Take 10% off for a shaded room. Then pick the next size up that is sold - window units come in 5,000, 6,000, 8,000, 10,000, 12,000 and 15,000 BTU.
Where to go next
See how far apart the answers run: Bullhead City, AZ, Houston, TX, San Francisco, CA.
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