What is a reefer truck? How the unit works, what it hauls and how reefer trucking pays

What "reefer" means in trucking

In trucking, a reefer is a refrigerated trailer. The word gets used loosely: drivers say "reefer truck," "reefer van," "reefer trailer" or just "reefer," and they all mean the same thing on a load board: a 48 or 53 ft enclosed trailer with insulated walls and a refrigeration unit mounted on the front wall.

A reefer truck is the whole rig, a semi tractor pulling that trailer. The tractor is an ordinary tractor. What makes it a reefer operation is the trailer and what it lets you haul: freight that has to stay cold, frozen or sometimes warm.

You'll also see smaller straight trucks with refrigerated boxes, used for local delivery. They work on the same principle, but this guide, and our dispatch service, is about tractors pulling 48 and 53 ft reefer trailers.

The reefer truck, piece by piece

A refrigerated trailer looks like a dry van from a distance. Up close, three things set it apart.

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The refrigeration unit. The box on the nose of the trailer is a self-contained refrigeration system with its own small diesel engine, compressor, fans and controller. Thermo King's Precedent S-610DE, a common trailer unit, lists a system weight of 1,919 lb and a 30 or 50 gallon fuel tank mounted under the trailer.

Insulated walls, floor and roof. Foam insulation sits between the outer skin and the inner liner. Hyundai Translead's ThermoTech reefer, for example, lists 2 in of insulation in the sides, floor and roof, 3 in in the rear door and 4 in in the front wall. That insulation is why a reefer is narrower inside than a dry van and weighs more empty.

A floor that moves air. Most reefer floors are grooved or ducted aluminum (often called a T-floor or duct floor) so cold air can travel under the pallets and back up through the load. Load it wrong and the air short-circuits, which is how loads end up warm in the middle. Our guide to reefer trailer dimensions has the inside measurements and pallet counts.

How a reefer unit works

A trailer unit uses the same cycle as a home refrigerator, just bigger and tougher. The unit's diesel engine drives a compressor. Refrigerant is compressed, gives off heat through the condenser coil on the outside of the unit, passes through an expansion valve and turns cold, then absorbs heat in the evaporator coil inside the trailer. A fan blows trailer air across that cold coil and back into the box.

Two sensors tell the controller what's happening. Return air is the temperature of air coming back from the load to the unit. Discharge air (or supply air) is the air leaving the unit into the trailer. The controller compares them with the setpoint, the temperature the shipper wants, and decides whether to cool, heat or idle.

Yes, heat. Reefers keep produce from freezing in winter the same way they keep it from warming in summer, and the same S-610DE sheet lists 39,000 BTU per hour of heating capacity next to its cooling figures.

Continuous vs cycle mode

Units run in one of two modes. In continuous mode the engine runs the whole time and air keeps moving through the load, which produce shippers usually want. In cycle mode (Thermo King calls it Cycle-Sentry, Carrier calls it start-stop) the unit shuts off when the box reaches setpoint and restarts when it drifts, which saves fuel and suits many frozen loads. The shipper's instructions on the bill of lading and rate confirmation decide which mode you run, not the driver. More on settings, pre-cooling and run time is in our guide to reefer temperature settings.

Reefer fuel

Because the unit has its own engine and tank, reefer operators buy fuel twice: tractor fuel and reefer fuel. Reefer fuel is often dyed diesel sold without on-road tax, since the IRS treats fuel burned in a separate motor that runs a refrigeration unit as an off-highway use. It never goes in the tractor. The tax rules, penalties and record keeping are in what is reefer fuel?.

What reefers haul

Anything that has to stay within a temperature range in transit. In practice, most reefer freight falls into a few groups:

• Produce: fruit and vegetables, usually chilled and often in continuous mode. The biggest seasonal swing in reefer freight.
• Frozen food: meat, poultry, seafood, ice cream, frozen vegetables and prepared meals.
• Dairy: milk, cheese, yogurt, butter. Steady volume, lots of multi-stop deliveries to grocery distribution centers.
• Fresh meat and poultry: chilled, often with strict sanitation and seal requirements.
• Beverages and confectionery: chocolate, candy, beer and wine that can't take summer heat or winter freezing.
• Pharmaceuticals and healthcare products: only for carriers whose equipment, monitoring and records meet the shipper's requirements.
• Flowers and plants: chilled and handled carefully.

Some reefer loads aren't temperature-sensitive at all. When dry van freight is tight, reefers often haul dry freight with the unit off, which is one reason reefer owners rarely sit for long.

For food, there's a federal layer on top of the shipper's instructions. The FDA's sanitary transportation rule (21 CFR 1.908) makes a carrier who has agreed to be responsible for temperature control meet the shipper's specifications, pre-cool the trailer as specified, and show the temperature was held if asked. Our guide to refrigerated freight walks through those duties.

Reefer trucking and reefer transportation, from the carrier's side

Reefer transportation is the part of the cold chain that happens on the road: a shipper with a cooled dock loads product into a pre-cooled trailer, the carrier holds the temperature, and the receiver checks it on arrival. For an owner-operator running reefer trucking under their own authority, a typical load goes like this:

1. Find and book the load. Most spot reefer freight is posted by brokers on load boards or offered directly to carriers they know. The rate confirmation lists the setpoint, mode, appointments and any lumper or detention terms. Where those loads come from is covered on our reefer loads page.
2. Pre-cool. If the shipper asks, run the empty trailer down to setpoint before the doors open.
3. Load and record. Check the setpoint on the bill of lading, take pulp temperatures of the product if asked, note the seal number.
4. Haul. Keep the unit fueled, watch the controller for alarms, and give the broker check calls.
5. Deliver. The receiver may check temperatures before unloading. If anything is questioned, the unit's temperature download is the record that matters.

On pay: reefer usually pays more per mile than dry van because the equipment costs more and the work has more risk. In DAT's figures for October 10-16, 2026, the national average reefer spot rate was $3.66 per mile and dry van was $3.09, both including fuel surcharge. Rates move every week, so check the current numbers in our reefer rates guide, and run any load through the reefer rate per mile calculator before you take it.

What a reefer driver does differently

Driving the truck is the same. The extra work is all about the box:

• Confirming the setpoint and mode on the paperwork match each other, and setting the unit to match.
• Pre-cooling when asked, and not opening doors longer than needed at the dock.
• Taking and recording pulp temperatures with a probe thermometer when the shipper or broker asks.
• Keeping the reefer tank fueled, and planning fuel stops around both tanks.
• Watching for unit alarms and reporting problems right away, with times and readings.
• Keeping the trailer clean and odor-free. Food shippers will turn away a dirty box.

A good reefer driver is also a good record-keeper. When a receiver rejects a load for temperature, the photos, readings and downloads decide who pays.

Pros and cons of reefer trucking

Whether it pays for you comes down to running the reefer side well: keeping the trailer loaded, keeping deadhead down and charging enough to cover the unit's fuel. If you're weighing the switch, start with our side-by-side of reefer vs dry van.