Calculate reefer unit fuel consumption in gallons from burn rate and run hours, estimate diesel cost, and find how long a full tank of fuel will last.
- All Automotive Calculators
- Idling Fuel Consumption Calculator
- Fuel Price Calculator
- Cargo Securement Tie-Down Calculator
Reefer Unit Fuel Consumption Formula
The calculator works in two directions. To find the diesel a reefer unit burns on a trip, it multiplies the burn rate by the number of hours the unit runs:
F = GPH * H
If you add pre-cool fuel or a diesel price, it extends the same result:
Total Fuel = (GPH * H) + Precool Cost = Total Fuel * Price
To find how long a tank of fuel will last, it divides the usable fuel by the burn rate:
Runtime = Tank / GPH
Variables:
- F is the diesel the reefer unit consumes, in gallons
- GPH is the burn rate of the unit in gallons per engine hour
- H is the number of hours the unit runs, including pre-cool and transit
- Precool is the extra diesel used to pull an empty trailer down to setpoint
- Tank is the usable fuel in the reefer belly tank, in gallons
- Price is the diesel price per gallon
The burn rate drives every result, so the calculator lets you handle it two ways. You can type it in if you already track it, or you can let the tool estimate it from three inputs: the operating mode, the setpoint, and the outside temperature. Continuous mode runs the engine without stopping and burns the most fuel. Cycle-Sentry, or start-stop, shuts the engine off once the box reaches setpoint and restarts when the temperature drifts, which lowers burn by roughly 15 to 25 percent. Colder setpoints and hotter outside air both push the rate up, because the unit has to pull out more heat. The estimate takes a base rate for the setpoint and multiplies it by a factor for the mode and a factor for the ambient temperature. Switching the top selector to the runtime mode uses the same burn rate to answer the reverse question of how many hours a given tank will last.
Reefer Diesel Burn Rates by Setpoint and Weather
These are typical burn rates in gallons per hour for a modern trailer unit such as a Carrier X4 or Thermo King Precedent running in continuous mode. Read across from your setpoint to the column that matches the outside temperature. Cycle-Sentry running comes in about 20 percent below the continuous numbers shown, and a multi-temp unit with separate zones runs higher.
| Setpoint | Mild (below 70F) | Moderate (70 to 90F) | Hot (above 90F) |
|---|---|---|---|
| Fresh produce or dairy (34F) | 0.55 | 0.65 | 0.88 |
| Fresh meat or chilled (28F) | 0.64 | 0.75 | 1.01 |
| Frozen (0F) | 0.77 | 0.90 | 1.22 |
| Deep frozen (-10F) | 0.85 | 1.00 | 1.35 |
Once you know the burn rate, this table shows how many hours different amounts of usable fuel will last. It answers the reverse question the cost tables on other sites skip: given the fuel in the tank, how many hours of cooling you have left before a refuel.
| Burn rate | 30 gal | 50 gal | 75 gal | 100 gal |
|---|---|---|---|---|
| 0.5 gal/hr | 60 hr | 100 hr | 150 hr | 200 hr |
| 0.7 gal/hr | 43 hr | 71 hr | 107 hr | 143 hr |
| 0.9 gal/hr | 33 hr | 56 hr | 83 hr | 111 hr |
| 1.1 gal/hr | 27 hr | 45 hr | 68 hr | 91 hr |
| 1.3 gal/hr | 23 hr | 38 hr | 58 hr | 77 hr |
Reefer Unit Fuel Consumption Example Problems
Example 1: Fuel used and cost on a frozen load.
You haul a frozen load with the unit set to 0F, running continuous in moderate weather, so the burn rate is about 0.90 gal/hr. The unit runs 18 hours total, which already includes a 2 hour pre-cool. Multiply the burn rate by the hours:
F = 0.90 * 18 = 16.2 gallons. At a diesel price of $3.90 per gallon, that is 16.2 * 3.90 = $63.18 in reefer fuel for the trip.
Example 2: How long a tank will last.
You have 50 gallons of usable fuel and the unit burns about 0.8 gal/hr in cycle mode on a frozen load. Divide the fuel by the burn rate:
Runtime = 50 / 0.8 = 62.5 hours, which is about 2.6 days if the unit runs 24 hours a day.
Frequently Asked Questions
How much fuel does a reefer unit use per hour?
Most modern trailer units burn between 0.4 and 1.5 gallons of diesel per engine hour. Around 0.5 to 0.9 gal/hr is typical at produce temperatures in moderate weather, while a deep frozen load in hot weather can reach 1.2 to 1.5 gal/hr. Running in cycle mode instead of continuous lowers the figure by roughly 15 to 25 percent, and an older unit burns more than a new one at the same setting.
Does the reefer run off the truck's fuel tank?
No. The reefer unit has its own diesel engine and its own belly tank, separate from the tractor. That tank usually holds about 50 gallons, though some trailers carry 75 or 100 for longer runs. You fuel it in a separate transaction at the pump, and you should watch its gauge as closely as the truck tank, because running it dry stops the cooling and can put the load at risk.
How can you lower reefer fuel consumption?
Run cycle mode when the freight can tolerate it, since frozen and solidly chilled loads usually can. Pre-cool the trailer on shore power at the dock so the engine is not burning diesel to pull the box down before loading. Keep the door seals and J-strip in good shape, since a leaky trailer can burn 30 to 40 percent more fuel. Keep the condenser coil clean and stay on the service schedule, because a fouled coil or a tired fuel pump quietly raises the burn rate over time.
