In order to correctly determine the right enclosure for a particular application, the total heat load to which the control panel will be subjected will need to be calculated. The total heat load in Btu (British Thermal Units) is a combination of (1) the amount of heat dissipated within the enclosure itself and (2) the amount of heat transferred from outside the enclosure to inside the enclosure. Follow the below steps to calculate Btu per hour:

- First, determine the approximate watts of heat generated within the enclosure:
- (Amount of heat in watts) x 3.41 = (Amount of heat in Btu/hr)

- Second, calculate the outside heat transfer as follows:
- Determine the surface area of the enclosure (in square feet ) exposed to the air, ignoring the top of the cabinet.
- Determine the temperature differential (in degrees Farenheit) between maximum surrounding temperature and desired internal temperature. Using the below Temperature Conversion Table, determine the Btu/hr/ft^2 for that differential. Multiplying the cabinet surface area times Btu/hr/ft^2 provides external heat transfer in Btu/hr.

- Add the internal and external heat loads together to determine the total heat load.