What size air conditioner for 200 square feet?
Around 7,000 BTU, with caveats that can move the number.
A 200 sq ft room with an 8 ft ceiling needs roughly 6,000 to 8,000 BTU/h. The right commercial unit is usually a 6,000 or 8,000 BTU model, not a 12,000.
The calculation, step by step
For a 200 sq ft room with an 8 ft ceiling, average insulation, two people and 20 sq ft of west-facing glazing with blinds:
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| Item | Watts | Where it comes from |
|---|---|---|
| Envelope and ventilation | 1,858 | 46.5 m³ x 40 W/m³ |
| Occupants | 240 | 2 people x 120 W |
| Solar gain | 195 | 1.86 m² x 150 W/m² x 0.7 (blinds) |
| Subtotal | 2,293 | |
| 10 % margin | 229 | |
| Total | 2,522 W | = 8,607 BTU/h = 0.72 tons |
How it shifts with your situation
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| Scenario | BTU/h | Unit |
|---|---|---|
| Well insulated, north facing, no direct sun | 6,300 | 6,000 BTU |
| Standard (the example above) | 8,600 | 8,000-9,000 BTU |
| Large unshaded west window | 9,600 | 9,000-10,000 BTU |
| Top floor, poor insulation, hot climate | 12,300 | 12,000 BTU |
If the room is a bedroom
A 200 sq ft bedroom usually needs less than a living room of the same size: fewer people, fewer appliances running, and it is used at night when there is no direct solar gain. A 6,000 BTU unit is often plenty, and it will run more continuously and quietly.
What it will cost to run
An 8,000 BTU unit of average efficiency draws about 700-800 W. At 8 hours a day and $0.17/kWh, that is roughly $1 a day, around $30 a month of heavy summer use.
Sources and methodology
Conversions use exact constants: 1 BTU/h = 0.29307107 W and 1 frigorie/h = 1 kcal/h = 1.163 W. The component sizing model (load per volume by insulation level, 120 W per person, solar gain by glazed area) is set out in full on the air conditioner size calculator. It is a guideline estimate: a professional heat-load calculation considers considerably more variables.
Frequently asked questions
How many BTU do I need for a 200 sq ft room?
Between 6,000 and 8,000 BTU/h under normal conditions. With poor orientation or insulation it can rise to 10,000-12,000.
Is a 12,000 BTU unit too big for 200 square feet?
Usually yes, unless it is a top-floor room with heavy sun or poor insulation. An oversized unit short-cycles and dehumidifies badly.
What size AC for a 200 sq ft bedroom?
6,000 BTU is typically enough: fewer occupants, fewer appliances and night-time use with no solar gain.
How much does it cost to run?
An 8,000 BTU unit draws roughly 700-800 W, so about $0.13 per hour at $0.17/kWh, or around $30 a month at 8 hours a day.
Does the same unit suit a living room and a bedroom?
Not necessarily. A 200 sq ft living room usually has more occupants, more appliances and more sun than a bedroom of the same size.