ENERGY STAR + ACCA Manual J
What Size Air Conditioner Do I Need?
For a single room, match the square footage to the ENERGY STAR table. For a whole house, size by climate. Here is both, the adjustments that change the answer, and a calculator.
Room AC Size by Square Footage (ENERGY STAR)
| Room Size (sq ft) | Capacity (BTU/hr) | Tons |
|---|---|---|
| 100 - 150 | 5,000 | 0.42 |
| 150 - 250 | 6,000 | 0.50 |
| 250 - 300 | 7,000 | 0.58 |
| 300 - 350 | 8,000 | 0.67 |
| 350 - 400 | 9,000 | 0.75 |
| 400 - 450 | 10,000 | 0.83 |
| 450 - 550 | 12,000 | 1.00 |
| 550 - 700 | 14,000 | 1.17 |
| 700 - 1000 | 18,000 | 1.50 |
| 1000 - 1200 | 21,000 | 1.75 |
| 1200 - 1400 | 23,000 | 1.92 |
| 1400 - 1500 | 24,000 | 2.00 |
| 1500 - 2000 | 30,000 | 2.50 |
| 2000 - 2500 | 34,000 | 2.83 |
Adjustments (ENERGY STAR): heavily shaded room, reduce 10%; sunny room, add 10%; kitchen, add 4,000 BTU. This table sizes a single room for a window, portable, or single-zone mini split.
By Room Size
200 sq ft
6,000 BTU (0.50 ton): a 5,000-6,000 BTU window or portable unit.
300 sq ft
7,000 BTU (0.58 ton): a 7,000 BTU window unit or a small mini split.
400 sq ft
9,000 BTU (0.75 ton): a 9,000 BTU (0.75 ton) window unit or mini split.
500 sq ft
12,000 BTU (1.00 ton): a 12,000 BTU (1 ton) mini split or large window unit.
600 sq ft
14,000 BTU (1.17 ton): a 14,000 BTU mini split or through-the-wall unit.
By House Size
1,000 sq ft
~20,000 BTU (2 ton typical): a 1.5-2 ton mini split or central system.
1,200 sq ft
~24,000 BTU (2 ton typical): a 2-2.5 ton central AC or multi-zone mini split.
1,500 sq ft
~30,000 BTU (2.5 ton typical): a 2.5-3 ton central air conditioner.
2,000 sq ft
~40,000 BTU (3.5 ton typical): a 3-4 ton central air conditioner.
2,500 sq ft
~50,000 BTU (5 ton typical): a 4-5 ton central air conditioner.
Size a Whole House by Climate
A house's load depends on climate, insulation, and windows, not just floor area. Enter your details for a Manual-J-style estimate and tonnage.
Frequently Asked Questions
What size air conditioner do I need for my room?
Match the room's square footage to the ENERGY STAR sizing table. A 100-150 sq ft room needs 5,000 BTU, 250 sq ft needs 6,000, 500 sq ft needs 12,000 (1 ton), and 1,000 sq ft needs 18,000. Then adjust: add 10% if the room is very sunny, subtract 10% if it is heavily shaded, and add 4,000 BTU if it is a kitchen. This table is for a single room served by a window, portable, or mini split unit; a whole house is sized differently.
How many BTU do I need per square foot?
For a single room, the ENERGY STAR table works out to roughly 20-30 BTU per square foot on smaller rooms and closer to 18-20 on larger ones. For a whole house, plan on about 18-20 BTU per square foot in a moderate climate, 22-25 in a hot climate, and 12-16 in a cold climate, because a house's load is driven by climate far more than a single room's is. A 1,500 sq ft house in a warm climate is about 30,000 BTU (2.5 tons).
Is it bad to oversize an air conditioner?
Yes. An oversized AC cools the air quickly but shuts off before it removes enough humidity, leaving the room cold and clammy and short-cycling the compressor, which wastes energy and shortens its life. ENERGY STAR specifically warns that bigger is not better. Size to the load, not above it, which is why a Manual J calculation matters for a whole-house system.
How many square feet does a 12,000 BTU (1 ton) AC cool?
About 450-550 square feet as a single room, per the ENERGY STAR table. One ton equals 12,000 BTU per hour. As a rough whole-house figure in a moderate climate (20 BTU per sq ft), 12,000 BTU covers roughly 600 square feet, but climate, insulation, windows, and ceiling height all shift that, so use a load calculation for a house.
What size AC for a 2,000 square foot house?
Roughly 3 to 4 tons (36,000-48,000 BTU), depending on climate. In a hot climate a 2,000 sq ft house can need close to 4 tons; in a cold climate it can be under 3. The exact size comes from a Manual J load calculation that accounts for your insulation, windows, orientation, and design temperature, not a flat rule. Use the calculator on this page to estimate by climate zone.
Related
BTU Calculator
Full climate-zone load sizing by insulation, windows, and duct location.
BTU Per Square Foot Chart
BTU/sq ft by climate zone and the tons-to-square-feet conversion.
Tonnage From Model Number
Decode the tonnage of an existing condenser from its model number.
Superheat & Subcooling
Once it is installed, verify the charge with a PT-based diagnostic.