9,000 BTU is where ductless mini-splits start. Nearly every brand sells a 9,000 BTU (three-quarter ton) single-zone head, and it is the usual bedroom head on multi-zone systems. In an average room it cools up to about 450 sq ft, with a best fit of 400 to 450 sq ft for a fixed-speed unit. Mini-splits are inverter driven and can throttle down well below their rating, so a 9,000 BTU head also works in rooms much smaller than 400 sq ft, which a window unit of the same size would short-cycle in.
Conditions move the ceiling. A shaded, well insulated room stretches to about 550 sq ft; a sunny, poorly insulated one stops around 350; a 10 ft ceiling brings it to 360.
Mini-splits are heat pumps, so the heating number matters as much. 9,000 BTU of heat covers about 220 sq ft in a moderate climate, 300 in a hot one, and 160 in a cold one. Heat pump output also falls as it gets colder outside: a standard model may deliver only 60 to 70 percent of its rating at 17°F. In a cold climate, compare the rated capacity at 5°F or 17°F, not the nameplate number.
9,000 BTU/hr is 2.64 kW, which is why the same unit is sold as a 2.6 kW split system outside the US. That kW figure is the heat the unit moves, not the power it uses. A 9,000 BTU mini-split draws roughly 600 to 800 W at full output, and a window unit of the same size about 820 W.
How many square feet a 9,000 BTU air conditioner cools
Largest room the unit keeps up with, rounded down to the nearest 10 sq ft. Two occupants, 8 ft ceiling and moderate climate unless the row says otherwise.
| Room | Cools up to |
|---|---|
| Shaded, good insulation | 550 sq ft |
| Average room (baseline) | 450 sq ft |
| Very sunny, poor insulation | 350 sq ft |
| Hot climate, very sunny | 370 sq ft |
| 10 ft ceiling | 360 sq ft |
| 4 people instead of 2 | 390 sq ft |
| Kitchen in the space | 250 sq ft |
How many square feet 9,000 BTU of heat covers
By climate and insulation. For a gas heater, use its output rating (input × efficiency).
| Climate | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| hot | 250 sq ft | 300 sq ft | 350 sq ft |
| moderate | 180 sq ft | 220 sq ft | 260 sq ft |
| cold | 130 sq ft | 160 sq ft | 190 sq ft |
9,000 BTU in kW, watts and tons
| Kilowatts | 2.64 kW |
| Watts | 2,638 W |
| Tons of cooling | 0.75 tons |
| Power an AC this size draws (EER 11) | about 818 W, 7.1 A at 115 V |
| Power an electric heater needs for this output | 2,638 W, 11.0 A at 240 V |
kW and watts here are heat output, the number on the box. An air conditioner moves that much heat while drawing far less electricity; an electric heater draws exactly as much as it puts out.
9,000 BTU questions
What is 9,000 BTU in kW?
2.64 kW. Divide BTU/hr by 3,412. That is cooling output; the unit itself draws much less electricity, around 600 to 800 W for a mini-split at full speed.
How many square feet does a 9,000 BTU mini-split cool?
About 450 sq ft in an average room, up to about 550 if the room is shaded and well insulated, and about 350 if it is sunny and poorly insulated. Because it is inverter driven, it also runs well in smaller rooms.
Is a 9,000 BTU mini-split big enough for a bedroom?
For almost any bedroom, yes. A 12 × 14 bedroom (168 sq ft) needs about 3,400 BTU/hr, and an inverter head throttles down to match. It is only too small if the bedroom is over about 450 sq ft or very sunny.