BTU is a term you'll hear everywhere when shopping for air conditioners. Understanding what it means is crucial for choosing the right AC.
What Does BTU Stand For?
BTU = British Thermal Unit
It's a unit of energy that measures heat. In air conditioning, BTU specifically measures the amount of heat an AC can remove from a room per hour.
BTU Definition in AC Context
1 BTU = the amount of heat needed to raise 1 pound of water by 1°F
In practical AC terms:
- A 10,000 BTU AC removes 10,000 units of heat per hour
- A 24,000 BTU AC removes 24,000 units of heat per hour
- Higher BTU = stronger cooling capacity
BTU vs Tonnage
BTU and tonnage are related:
- 1 ton = 12,000 BTU/hour
- 12,000 BTU = 1 ton
- 24,000 BTU = 2 tons
- 36,000 BTU = 3 tons
What Size BTU AC Do I Need?
Use this simple formula:
Room Size (sq ft) × 25 = Required BTU
Examples:
- 100 sq ft room: 100 × 25 = 2,500 BTU
- 200 sq ft room: 200 × 25 = 5,000 BTU
- 400 sq ft room: 400 × 25 = 10,000 BTU
- 500 sq ft room: 500 × 25 = 12,500 BTU
Factors That Increase BTU Needs
Climate
- Hot climate (35°C+): Add 10-20%
- Very hot climate (40°C+): Add 20-30%
Sun Exposure
- High sun exposure: Add 10%
- Moderate sun: Add 5%
- Shaded room: No addition needed
Ceiling Height
- 10 ft ceiling: Add 5%
- 12 ft ceiling: Add 15%
- Above 12 ft: Add 20-25%
Occupancy
- Each person generates ~600 BTU heat
- Add 600 BTU per person above 2 occupants
Kitchen/Heat Sources
- Kitchen or adjacent to kitchen: Add 4,000 BTU
- Computers/servers: Add 1,000-3,000 BTU
- Multiple appliances: Add accordingly
Factors That Decrease BTU Needs
- Excellent insulation: Subtract 10-15%
- Double-glazed windows: Subtract 5%
- Shaded location: Subtract 5-10%
- Basement or interior room: Subtract 5%
Window vs Portable vs Split AC BTU
The BTU rating is the same regardless of AC type:
- Window AC: 5,000-15,000 BTU
- Portable AC: 8,000-14,000 BTU
- Split AC (indoor): 9,000-48,000+ BTU
What If I Choose Wrong BTU?
Too Low (Undersized)
- AC runs constantly but doesn't reach set temp
- Higher electricity bills
- Shorter lifespan
- Poor humidity control
Too High (Oversized)
- Cools quickly but short-cycles
- Higher power bills despite quick cooling
- Poor dehumidification
- Temperature fluctuations
Quick BTU Reference Chart
- Up to 150 sq ft: 5,000 BTU (0.42 ton)
- 150-250 sq ft: 10,000 BTU (0.83 ton)
- 250-350 sq ft: 12,000 BTU (1 ton)
- 350-450 sq ft: 15,000 BTU (1.25 ton)
- 450-550 sq ft: 18,000 BTU (1.5 ton)
- 550-700 sq ft: 24,000 BTU (2 ton)
Conclusion
BTU is the measure of an AC's cooling power. Proper BTU sizing ensures your AC works efficiently without wasting energy. Use our free BTU calculator to determine the exact capacity your room needs.