Calculate Energy Consumption

A/C Sizing Calculator

It's very important that you select the right sized unit for your home. An undersized unit will not have the ability to effectively handle the heat in your room, causing the unit to overwork and not perform optimally. On the other hand, an oversized unit can cool a room quickly, but can create a "cold and clammy" feel due to the humidity levels that aren't lowered properly.  We have provided a quick and easy guide to estimating a proper-sized air conditioner to fit your needs.

1. Compute the Area of the Room: Assumes an 8-foot ceiling.

(Use Tab key to advance to the next field)

square ft

2. Select your Air Conditioning Needs:

In what environment will you be using your air conditioner?

  • Low Heat or Night Time Only - windows/exterior walls mostly shaded from direct sunlight, well-insulated construction. Good figure for bedrooms or apartments in well-constructed high-rise buildings.
  • Normal Conditions - windows/exterior walls moderately (50-70%) exposed to direct sunlight, ceiling with attic space above.
  • High Heat or Direct Sunlight - large window and wall area exposed to direct sunlight, heavy afternoon sun, and open beam ceilings.

(Use your mouse to select the appropriate choice)

Note: Add 4,000 BTUs if the area includes a kitchen

3. Compute the Monthly Usage Hours:

How much will this unit cost to operate?

The Energy Efficiency Ratio, or EER rating, tells you how efficient the appliance is in energy consumption. The higher the number rating, the more energy-efficient it is. Here is an example of how much it would cost to run your selected unit if it had an 8, 10, or 11 EER rating:

Estimate length the A/C will be on:


4. Select Service Area for Monthly Energy Cost by EER:

Energy Efficiency Ratings

Your Energy Cost should be between:



B. 10.0 EER


C. 11.0 EER


* EER value for box A can be changed to illustrate costs of Air Conditioners with other EER ratings.

** Default cost per kWh is based on the average 2017 residential rates for customers on Oahu and Maui Island.

Sizing of a room air conditioner depends on many factors, such as area of room, ceiling height, number of occupants, insulation and type of construction. We recommend you consult with the sales person at the showroom you visit to be sure that the size selected will meet your individual requirements.