A second engine, running
The refrigeration unit has its own diesel motor and its own tank, and on a frozen load it runs for the length of the trip whether the truck is moving or parked overnight. That fuel is burned on your load and billed to it.
Temperature-controlled truckload
Reefer shipping: what the temperature column actually buys
A reefer is a dry van with a second diesel engine bolted to the nose and a set of legal duties attached to the load inside it. This page covers where the premium over a dry van comes from, why the unit's operating mode changes what arrives, and what a temperature claim has to contain to survive. Rules cited are from the Code of Federal Regulations and the unit manufacturer's own manual, read 2026-07-28.
CFR duties by partyMode wording quotedClaim deadlines cited
Priced by a person
Truckload work is quoted against a lane, a season and a commodity. No rate on this page, and none worth inventing.
What SMKlog does with a reefer request
Plain scope first. SMKlog sells US domestic parcel labels straight from the site with no account, and it takes temperature-controlled truckload requests through a review where a person prices the move. We do not own trailers or reefer units, we do not sell the coolant, and our own checkout will not label perishable or temperature-controlled goods. Anything below that describes what a carrier does is describing the carrier.
That also settles the pricing question honestly. A reefer rate is a function of lane balance, produce season, commodity and the fuel the unit burns while it sits, and none of those live in a published table. What follows is the part that is knowable in advance: the duties, the mode, and the paperwork.
Where the premium over a dry van comes from
Nobody charges extra for the paint. The gap between a reefer rate and a dry van rate on the same lane is built out of four specific things, and each of them is either fuel, labor or time that the dry van never spends.
Pre-cool before the first pallet
Federal rule requires the carrier to bring the compartment down to the shipper's number before offering the trailer. That is dead time at the yard, and it is time nobody drives during.
Washouts between commodities
A trailer that carried raw protein cannot take produce next without being cleaned, and the carrier has to hold written procedures covering how it cleans and inspects. Every washout is an unpaid stop.
A thinner trailer pool
Reefers are a minority of the national trailer fleet and they chase seasonal harvest lanes. When a region is in season, the equipment leaves the other lanes and the price on those lanes follows.
Which of the four dominates changes by month. Fuel is the steady part; equipment scarcity is the part that produces the sharp weeks. Both are lane-specific enough that a percentage over dry van quoted in advance would be a guess dressed up as a figure.
Continuous or cycle: the setting that changes your product
Every reefer unit runs in one of two modes, and the difference is not a detail for the driver to sort out. Thermo King describes both in the operator manual for its Precedent single-temperature trailer units (TK 56218-2-OP-EN, Revision B June 2021, published at thermoking.com and read 2026-07-28).
| Mode | What the manual says it does | What that does to a load |
|---|---|---|
| Cycle Marketed as a start-stop fuel saving system | The unit “will start and stop automatically to maintain setpoint, keep the engine warm, and the battery charged.” | Between cycles the fans stop with the engine. Air stops moving through the load, warm air pools at the doors and near the roof, and the box temperature swings around the setpoint rather than sitting on it. |
| Continuous The default when the cycle icon is absent from the display | The unit “starts automatically and runs continuously to maintain setpoint and provide constant airflow.” | Air keeps circulating whether the unit is calling for cooling or not, so the pallet in the nose and the pallet at the doors see something close to the same conditions. |
Constant airflow is the whole argument. Frozen product is a thermal mass and tolerates a stopped fan for a while. Fresh produce respires and gives off its own heat, chilled protein needs the air moving to hold an even temperature across the deck, and anything with a validated storage range gets judged on the warmest carton rather than the average. For those, cycle mode saves fuel the carrier pays for and costs product you pay for.
The fix is administrative rather than mechanical. Name the mode on the bill of lading next to the setpoint, in the same line of text, so it is part of the instruction rather than a conversation at the gate. A driver following a written setpoint with no mode named will run whatever the unit was left in.
Who owes what, in writing
For food that needs temperature control for safety, the duties are split across four parties by 21 CFR part 1 subpart O, the Food and Drug Administration's sanitary transportation rule. The section text below was read at govinfo.gov on 2026-07-28. Reading it once saves the argument later, because it tells you exactly whose signature is missing when something arrives warm.
| Party | Duty | Cite |
|---|---|---|
| Shipper | Specify an operating temperature to the carrier in writing, including the pre-cooling phase where necessary. One notification covers the relationship until something changes, and then a fresh written notice goes out before the next shipment. | 1.908(b)(2) |
| Loader | Verify before loading that each mechanically refrigerated compartment is prepared, including that it has been properly pre-cooled if that was called for. | 1.908(c)(2) |
| Carrier | Pre-cool each refrigerated compartment as the shipper specified, before offering the equipment for the load. | 1.908(e)(3) |
| Carrier | After the run, on request, supply the operating temperature the shipper specified and demonstrate that it was held. The rule accepts ambient readings at loading and unloading, or time and temperature data taken during the shipment. | 1.908(e)(2) |
| Receiver | On arrival, assess whether the food was subjected to significant temperature abuse, by means such as taking the product temperature, reading the vehicle's ambient temperature and its setting, and a sensory check for off odors. | 1.908(d) |
| Anybody in the chain | On becoming aware of a possible material failure of temperature control, hold the food back from sale or distribution until a qualified individual determines the deviation did not render it unsafe. | 1.908(a)(6) |
Two practical consequences fall out of that table. The first is that a shipper who never put a number in writing has no standard to measure the carrier against, which quietly ends most temperature disputes before they start. The second is that the receiver's inspection is a duty rather than a courtesy, so a consignee who signs clean and opens the pallets on Monday has handed the carrier its defense.
Records under 21 CFR 1.912 are kept for 12 months beyond the life of the agreement or procedure, must be produced promptly on request, and where they are stored offsite they have to be retrievable within 24 hours. The exception is the carrier's written cleaning and inspection procedure, which stays onsite for as long as it is in use.
What a temperature claim has to contain
Cargo claims against a motor carrier run on 49 CFR part 370, read at ecfr.gov on 2026-07-28. The rules are short, and almost every rejected claim fails on one of the first two.
- It has to be in writing, and it has to name a number. The minimum filing requirements are a written communication that contains facts sufficient to identify the shipment, asserts liability for the loss or damage, and makes claim for payment of a specified or determinable amount of money. An email that says the load arrived warm and asks what the carrier intends to do is not a claim.
- A note on the delivery receipt is not a claim either. The rule says so directly: bad order reports, appraisal reports, notations of shortage or damage on freight bills or delivery receipts, and carrier inspection reports do not on their own meet the filing requirement, whether or not they carry a dollar figure. Write the exception on the receipt anyway, then file the claim separately.
- Support it with the documents the rule expects. Investigation is built on the bill of lading, evidence of the freight charges, and the invoice or a certified extract of it establishing value. For a temperature case, add the setpoint instruction you issued in writing and whatever the carrier produced under 21 CFR 1.908(e)(2).
- Then watch two clocks that belong to the carrier. Acknowledgement of a properly filed claim is due in writing within 30 days. Disposition follows: the carrier must pay, decline, or make a firm compromise settlement offer within 120 days, and if it cannot, it owes you a written status update at that point and at the end of every 60-day period after it.
- And two that belong to you. Federal law bars a carrier from providing a period shorter than 9 months for filing a claim, or shorter than 2 years for bringing a civil action, counted from written notice that part of the claim was disallowed. An offer of compromise is not a disallowance unless the carrier says so in writing with reasons.
The sequencing matters more than the paperwork. Product temperature taken at the dock, photographed with the trailer's display in the same frame, is worth more than a laboratory report a week later, because the carrier's defense is almost always that the load left the shipper warm.
Reefer questions
How much more does a reefer cost than a dry van?
More, on every lane, and by an amount nobody can publish honestly as a single number. The gap is built from a second diesel engine burning fuel for the whole run, pre-cool time before loading, washouts between commodities, and a smaller pool of trailers competing for the same freight. Season and direction move it as much as mileage does, which is why a person prices the lane rather than a table.
What is the difference between continuous and cycle mode?
Thermo King's operator manual puts it in two sentences: in cycle mode the unit starts and stops automatically to maintain setpoint, keep the engine warm and the battery charged, while in continuous mode it runs without stopping to maintain setpoint and provide constant airflow. The airflow is the part that decides your load.
Who is responsible for setting the temperature?
The shipper. Under 21 CFR 1.908(b)(2) a shipper of food needing temperature control must specify an operating temperature to the carrier in writing, including the pre-cooling phase where that is necessary. A carrier holding a trailer at whatever the last customer asked for is doing exactly what the paperwork told it to.
What temperature records can I ask a carrier for?
Once the run is finished, 21 CFR 1.908(e)(2) lets a shipper or receiver ask the carrier to demonstrate that it held the temperature the shipper specified. The rule names ambient measurements at loading and unloading, or time and temperature data taken during the shipment, as acceptable ways to do it.
How long do I have to file a temperature claim?
Check the bill of lading, because that is where the period lives, but it cannot be short. Federal law bars a carrier from allowing less than 9 months to file a claim and less than 2 years to bring a civil action after written disallowance. Waiting out either window is the most common way a valid claim dies.