Sizing an air conditioner for 500 square feet seems simple enough. It’s not all that difficult to figure out how many BTUs do you need to cool 500 sq ft of living space.
Nonetheless, many people get the BTUs wrong. That’s why we will explain how you go about figuring out how many BTUs air conditioners you need to cool 500 sq ft. We need to account for sun exposure, insulation, and ceiling height to get an adequate estimation.
Note: At the end, you can also check recommendations for 500 sq ft AC units.
Let’s start with an example to see where most people make a mistake when choosing a 500 sq ft air conditioner size.
‘How many BTUs for 500 sq ft for adequate cooling?’
Simple answer: 10,000 BTU to 12,000 BTU. We get 10,000 BTU by using the AC rule of thumb sizing method (’20 BTU per sq ft of living space’; hence 20×500 sq ft = 10,000 BTU). 12,000 BTU is an Energy Star recommended size of AC for 450-550 sq ft areas.
Air conditioner size for 500 sq ft is between 10,000 BTU to 12,000 BTU. The key here is to understand that you have to adjust this number a bit. Increasing or decreasing this number will provide for a more adequate 500 sq ft AC sizing for your situation.
3 Key Factors That Increase/Reduce BTU Requirement For 500 Sq Ft
2 factors – sun exposure and insulation – play a major role here. They need to be taken into account if you want to correctly figure out how many BTUs do you need for 500 sq ft.
Namely, you have to:
- Add 1,000 BTU if the 500 sq ft area is very sunny (several windows, above-average sun exposure).
- Reduce by 1,000 BTU if the 500 sq ft area is heavily shaded (1 or 2 windows, below-average sun exposure).
- Add 2,000 BTU if your insulation is very subpar (very low R insulation values; generally, older buildings).
- Reduce by 2,000 BTU if your insulation is very good (high R insulation values; generally, newer buildings).
Another important factor you have to account for is the ceiling height. Most estimates for how many BTUs you need for 500 sq ft are made for 8 ft ceilings. What happens if you have a 10 ft ceiling, or a 12 ft ceiling?
The BTU requirements to cool a 500 sq ft room with higher ceilings increase, obviously. The question is by how much.
Here’s the simplest rule:
Add 1,250 BTU for every additional foot over an 8 ft ceiling.
Example: 10,000 BTU air conditioner will probably be enough to cool a 500 sq ft 8 ft ceiling area. What if this space has a 10 ft ceiling instead of an 8 ft ceiling?
You add 2×1,250 BTU = 2,500 BTU to 10,000 BTU. That means that instead of 10,000 BTU AC, you would do better with a 12,500 BTU unit.
To help you out, we have calculated 500 sq ft BTU requirements for cooling a space with higher ceilings:
| Ceiling Height (Ft): | BTUs For 500 Sq Ft: |
| 6 ft ceiling | 7,500 BTU |
| 7 ft ceiling | 8,750 BTU |
| 8 ft ceiling | 10,000 BTU |
| 9 ft ceiling | 11,250 BTU |
| 10 ft ceiling | 12,500 BTU |
| 11 ft ceiling | 13,750 BTU |
| 12 ft ceiling | 15,000 BTU |
| 13 ft ceiling | 16,250 BTU |
| 14 ft ceiling | 17,500 BTU |
| 15 ft ceiling | 18,750 BTU |
| 16 ft ceiling | 20,000 BTU |
As you can see, if you have a 16 ft ceiling, you will have to install a 20,000 BTU AC to adequately cool a 500 sq ft area. This is because you’re cooling the volume of air, and the volume of air increases with the increasing ceiling height.
In most cases, you will need either a 10,000 BTU or 12,000 BTU AC unit for 500 sq ft. We have summarized the recommendations for best AC units in two following lists/articles:
- Best 10,000 BTU air conditioners (for 300-500 sq ft).
- Best 12,000 BTU air conditioners (for 400-600 sq ft).
You can check both of these lists of window, portable, and mini-split ACs and choose one that best fits your specific sun exposure, ceiling height, insulation, and so on.
You can also check how to determine the cooling BTU requirements with this BTU calculator.