Reefer Fuel Consumption

A refrigeration unit's job is to remove heat leaking into the trailer from outside, and the rate of that heat leak scales with how much hotter the outside air is than the target cargo temperature -- not with the setpoint alone. A trailer set to 35°F on a 90°F day works harder than one set to 35°F on a 50°F day, even though the setpoint is identical, because the unit has to fight a much bigger temperature gap in the first case.

A multi-temperature unit divides the trailer into separate compartments held at different temperatures, which means running multiple refrigeration circuits (or a more complex single circuit serving multiple evaporators) simultaneously rather than cooling one uniform space. That added mechanical complexity and the need to maintain multiple temperature zones independently is why this calculator applies a higher fuel-consumption adjustment for multi-temperature units.

A denser, fuller load has more thermal mass that needs to be actively cooled and held at temperature, and a fully packed trailer often has less air gap around the cargo for cold air to circulate efficiently, both of which increase the refrigeration unit's workload compared to a lightly loaded (LTL) trailer with more open space and less mass to cool.

Treat it as a general planning estimate rather than a model-specific figure -- actual fuel consumption varies with the transport refrigeration unit's specific model, age, maintenance condition, and even ambient humidity, none of which this calculator's simplified adjustment factors capture individually. If your fleet tracks actual fuel-per-hour data for your reefer units, that real data will be more accurate than this general estimate.