You will have to pay more to shiploads that require refrigeration, compared to regular dry van loads. Reefer units require additional fuel to operate and keep the temperature, which is what affects the rate. The cooling units also make the trailer heavier.

In the case of refrigerated trucks, the cargo compartment is sealed to prevent heat from entering, and a refrigeration system is used to prevent the temperature from dropping when the doors are opened. The cargo compartment is sealed and insulated against heat by way of a sort of polymer form, which allows temperatures to stay fairly stable even before the use of a refrigeration system. If the reefer system is not running, it will take a while before the temperature inside the cargo compartment drops to a problematic level.