How to use
- Multiply the floor length by width, or enter an already measured floor area.
- Select the exposure that describes the room and enter its regular number of occupants.
- Mark kitchen use when applicable. Calculate to see the chart capacity and each added load separately.
How the estimate is calculated
The first ENERGY STAR chart row whose upper area limit covers your room sets the base capacity. Heavy shade multiplies it by 0.9, while strong sun multiplies it by 1.1. Add 600 BTU/h for each regular occupant beyond two and 4,000 BTU/h for kitchen use. The result is a cooling rate in BTU per hour.
Example: a 300 sq ft room with normal exposure, two regular occupants, and no kitchen uses the chart's 7,000 BTU/h base. No adjustment applies, so its estimated capacity is 7,000 BTU/h.
ENERGY STAR room capacity chart
| Area upper limit (sq ft) | Base capacity (BTU/h) |
|---|---|
| 150 | 5,000 |
| 250 | 6,000 |
| 300 | 7,000 |
| 350 | 8,000 |
| 400 | 9,000 |
| 450 | 10,000 |
| 550 | 12,000 |
| 700 | 14,000 |
| 1,000 | 18,000 |
| 1,200 | 21,000 |
| 1,400 | 23,000 |
| 1,500 | 24,000 |
| 2,000 | 30,000 |
| 2,500 | 34,000 |
Source: ENERGY STAR Room Air Conditioners. The published chart starts at 100–150 sq ft and assumes 8 ft ceilings. This tool selects 5,000 BTU/h below the chart's first band as a planning floor, without claiming a tested recommendation for such a small room. Areas beyond 2,500 sq ft are rejected rather than extrapolated.
Adjustments from the same guide
- Heavy shade: reduce chart capacity by 10%.
- Very sunny exposure: increase chart capacity by 10%.
- More than two regular occupants: add 600 BTU/h for each extra person.
- Kitchen installation: increase capacity by 4,000 BTU/h.
For instance, the 500 sq ft sunny-room case with four occupants is 12,000 × 1.1 + 1,200 = 14,400 BTU/h. These adjustments are applied in that order, rather than increasing the occupant and kitchen additions by the sunlight percentage.
A room estimate has limits
Ceiling height, air leakage, large windows, and connected spaces can make the chart a poor fit. It does not estimate whole-house heating or cooling loads and does not replace Manual J sizing. A taller ceiling does not get an invented multiplier here. Discuss rooms outside the chart assumptions with the installer.
Common mistakes
- Using the whole home's area for a unit intended to cool one room.
- Treating BTU/h as electricity consumption instead of cooling capacity.
- Adding a person allowance for the first two occupants.
- Assuming that the largest unit available will necessarily control humidity well.
Sources
ENERGY STAR Room Air Conditioners: floor-area capacity table, 8 ft ceiling assumption, and the four heat adjustments, as reviewed for this estimate. Metric floor area is converted to square feet before chart selection.
Related calculators
- Insulation Calculator — attic R-value planning
- Square Footage Calculator — find the room floor area
Frequently asked questions
Is this for central air conditioning?
It is intended for room air conditioners. A whole-house system needs a load calculation that accounts for the building and its individual rooms.
What if my ceiling is taller than 8 feet?
The source chart assumes 8 ft ceilings. Have the actual room evaluated rather than treating this estimate as a final capacity selection.
Does the result give electrical watts?
The output is BTU per hour of cooling capacity. Electrical input depends on the efficiency and operating conditions of the particular appliance.
How is sunlight applied?
The shade or sun factor changes the chart base first. Occupant and kitchen loads are added afterward.
Why is an area over 2,500 square feet rejected?
That is the upper end of the ENERGY STAR room air conditioner sizing chart. The tool does not extend the table beyond its source.