A reefer truck is a refrigerated truck or trailer equipped with a built-in cooling system that maintains a controlled temperature during transit. The name “reefer” is simply industry shorthand for “refrigerated.” These vehicles haul everything from frozen meat and fresh produce to pharmaceuticals, keeping cargo at precise temperatures from the warehouse to the delivery point.
How the Refrigeration Unit Works
The cooling system on a reefer trailer operates on the same basic cycle as your home refrigerator, just scaled up significantly. A chemical refrigerant circulates through three main components in a continuous loop.
The cycle starts at the compressor, which squeezes refrigerant gas until its pressure and temperature rise. That hot, high-pressure gas flows into the condenser, a set of coils mounted on the outside of the trailer. As outside air passes over the coils, the gas releases its heat and cools down enough to condense into a liquid. The liquid refrigerant then moves through an expansion valve, which drops its pressure sharply. Finally, the cold, low-pressure refrigerant enters the evaporator inside the trailer. There, it absorbs heat from the cargo space, evaporating back into a gas in the process. That gas returns to the compressor, and the loop starts again.
The result is a trailer interior that can be held at a specific temperature, whether that’s well below zero or just above freezing, for the entire duration of a trip.
Temperature Ranges by Cargo Type
Different products require very different settings, and even a few degrees of drift can ruin a load. Frozen freight typically needs temperatures between 0°F and negative 10°F. Some products, like ice cream, require even colder settings. Fresh and refrigerated goods like produce, dairy, and deli items sit in a much narrower band, usually 32°F to 36°F. Pharmaceuticals and certain chemicals also travel in reefer trailers, though their required ranges vary by product.
Drivers or dispatchers set the target temperature on the unit’s digital controller before loading. Sensors inside the trailer monitor conditions continuously, and many modern units transmit real-time temperature data back to the carrier and the shipper. If the temperature drifts outside the acceptable window, the system can trigger alerts so the driver can respond before the cargo is compromised.
Fuel and Operating Costs
One detail that surprises people outside the trucking industry: a reefer unit has its own separate diesel engine and its own fuel tank, independent of the truck’s main engine. This means the refrigeration keeps running even when the truck is parked, turned off, or waiting at a loading dock.
That dedicated engine burns fuel constantly while the unit is operating. Older reefer units consume roughly 1 to 3 gallons of diesel per hour, depending on the load and how hard the system is working. Newer units are considerably more efficient, using between 0.4 and 1.1 gallons per hour. Over a multi-day cross-country haul, fuel for the reefer unit alone can add up to hundreds of dollars on top of the truck’s normal fuel costs.
This is a major reason refrigerated freight costs more to ship than dry goods. The shipper pays not only for the truck and driver but also for the continuous fuel burn of the cooling system, along with the higher maintenance costs that come with a second engine and all its components.
Standard Trailer Dimensions
The most common reefer trailer on American highways is 53 feet long and 8.5 feet wide, the same exterior footprint as a standard dry van trailer. However, the interior cargo space is slightly smaller because the insulated walls and the evaporator unit eat into the usable volume. Wall insulation is typically 2 to 3 inches thick on each side, and the evaporator assembly takes up space near the front of the trailer.
That reduced interior space means you can’t always fit as many pallets in a reefer as you can in a dry van of the same exterior length. Carriers and shippers account for this when planning loads, and it’s another factor in the higher per-unit shipping cost of refrigerated freight.
Who Uses Reefer Trucks
Grocery chains and food distributors are the most obvious customers, but the range of industries that depend on refrigerated transport is broader than most people realize. Restaurants, meal kit companies, floral distributors, pharmaceutical manufacturers, and even cosmetics companies all ship temperature-sensitive products in reefer trailers. Seasonal demand spikes are common: produce harvests in summer and fall, frozen turkeys before Thanksgiving, and vaccine distribution campaigns all put pressure on reefer capacity and rates.
For truck drivers, hauling reefer loads generally pays more per mile than pulling a dry van, reflecting the added complexity of maintaining temperature compliance and the higher cost of equipment. Many carriers specialize exclusively in refrigerated freight because of the expertise, equipment investment, and food safety certifications involved.
The Shift Toward Zero-Emission Units
Traditional reefer units run on diesel, which means they produce emissions independent of the truck itself. Regulators are pushing the industry toward cleaner alternatives. Zero-emission transport refrigeration units use battery-powered compressors, fans, and controls instead of a diesel engine. To qualify as truly zero-emission, the batteries cannot be recharged by the truck’s own engine, axle, or any other vehicle-powered mechanism. They’re charged from the electrical grid, either at a depot or through shore power connections at warehouses.
Adoption is still in the early stages, but fleet operators buying new equipment are increasingly weighing electric reefer units against traditional diesel ones, factoring in both regulatory timelines and the long-term fuel savings that come with eliminating that 0.4-to-3-gallon-per-hour diesel burn.