A genset (generator set) is a portable diesel generator that clips onto a refrigerated container or its chassis to keep the reefer unit running while the box travels over the road. At sea and in the terminal, a reefer plugs into ship or yard power; on a truck, there is no outlet — the genset is what keeps the cargo at temperature between the port and the warehouse. For perishables moving through PortMiami and Port Everglades, genset availability is a make-or-break detail of reefer drayage.
How gensets work
A genset is a self-contained diesel engine and generator producing 460V three-phase power, the standard for reefer units. It bolts or clips onto the container in one of two configurations:
Clip-on vs. underslung
A clip-on genset mounts on the front wall of the container, above the chassis neck. An underslung genset mounts beneath the chassis frame. Clip-ons are faster to install and swap; underslungs keep the center of gravity lower and are common on dedicated reefer chassis. Both run 12-24+ hours on a fuel tank, more than enough for local Miami drayage runs.
When you need one
Any time a loaded reefer container moves by truck for more than a short hop, or sits at a facility without reefer plugs, it needs a genset. Typical cases: port-to-warehouse moves for produce, seafood, and frozen goods; pharma cold chain shipments that cannot tolerate temperature excursions; and transloads where the box waits at a dock. If the receiving warehouse has reefer outlets, the genset comes off at delivery; if not, it stays on the box, and you pay for the extra days.
What a genset costs
In South Florida, expect roughly $100-$200 per day for genset rental plus fuel, billed as an accessorial on top of the base drayage rate. Fuel burn is typically around 3-4 liters per hour depending on the reefer’s setpoint and ambient heat — and Miami ambient heat is no joke. Carriers that own gensets, rather than renting them per move, can quote more predictable rates. That is one of several accessorials explained in our guide to accessorial charges in freight.
Genset tips for Miami importers
Book the genset when you book the drayage, not after the box discharges — supply tightens during produce season. Confirm the reefer’s temperature setpoint and continuous vs. cycle-sentinel mode in writing. Ask whether your carrier owns gensets and reefer-capable chassis or depends on third-party rentals. And verify the receiving facility’s power situation in advance so you are not paying for genset days you do not need. For more on the equipment side, see our explainer on reefer containers.
Frequently asked questions
Does every reefer container move need a genset?
No. A reefer needs a genset only while it is off ship or yard power with cargo that must stay at temperature. Short repositioning moves of empty reefers, or moves where the box is immediately plugged in at destination, may not require one.
How long can a genset run on one tank?
Most gensets run 12 to 24 hours or more on a full diesel tank, depending on tank size, the reefer setpoint, and ambient temperature. That comfortably covers local South Florida drayage, but long-haul moves need refueling plans.
Who supplies the genset, the ocean carrier or the trucker?
Usually the drayage carrier arranges the genset, either from its own fleet or a rental pool, and bills it as an accessorial. Some ocean carriers offer genset programs, but availability is limited, so most importers rely on their trucker.
Go Freight moves temperature-controlled containers daily at PortMiami and Port Everglades with owned trucks and chassis. Get a reefer drayage quote or call (786) 445-0150.