AC size for a 800 sq ft room
16,000 BTU
for a 800 sq ft room (1.3 tons) · about 1,333 W at EER 12
Adjust for the room
| Condition | BTU/h |
|---|---|
| Normal room | 16,000 |
| Very sunny (+10%) | 17,600 |
| Shaded (−10%) | 14,400 |
| Kitchen (+4,000) | 20,000 |
| Each extra person over 2 (+600) | +600 |
Rule of thumb: 20 BTU per sq ft with 8 ft ceilings (ENERGY STAR sizing guidance).
Monthly running cost at $0.17/kWh
| Use | Energy | Cost |
|---|---|---|
| 4 h/day | 160 kWh | $27 |
| 8 h/day | 320 kWh | $54 |
| 12 h/day | 480 kWh | $82 |
FAQ
What size AC for 800 square feet?
About 16,000 BTU (1.3 tons); add 10% for a sunny room and 4,000 BTU for a kitchen.
How much does it cost to run a 16,000 BTU AC?
At roughly 1,333 W, 8 hours a day for a month uses 320 kWh, about $54 at $0.17/kWh.