It is very important to come up with an accurate BTUs needed number. An air conditioner that is overworked will run constantly and quickly add a significant amount to your energy bill. An air conditioner that is too powerful will cycle on and off frequently, wasting energy, and will not extract humidity from the air well, either. The end result will be a cold, damp room, and that moisture can damage any number of items in the space that you are cooling (old papers? photos? paintings? etc.)
You can read a handy table on size and BTU here, but you should also keep in mind that several factors can slightly alter this standardized table’s numbers.
Here are some conditions that will alter your BTUs-needed calculation.
- If the room/space that you are cooling gets a lot of shade during the day, you can reduce your BTU need by 10%.
- Conversely, if the room/space that you are cooling gets a lot of sun during the day, you should increase your BTU need by 10%.
- If the room/space that you are cooling has more than two people in it on a consistent basis, add 600 BTUs for each person. For instance, if you are seeking to cool an office space that is used all day by four people, increase your BTU need by 2400. Human beings produce a lot of heat in a room.
- If your room/space is part of a larger structure that does not have good insulation and/or is drafty, you should increase your BTU need by 30-50%.
- If your ceilings are higher than 8’, increase the number of BTUs needed.
- If you are placing an air conditioner in a kitchen, add 4,000 BTUs to your total.