When a reefer container leaves the terminal, it loses its shore power connection. The truck engine powers the refrigeration unit during transit — but once you drop that box at a yard, a warehouse dock, or a staging area without plugin access, you need another power source. That's what a genset does. For anyone moving temperature-sensitive cargo through South Florida, understanding genset containers is non-negotiable.
What a Genset Container Actually Is
A genset (short for generator set) is a diesel-powered generator mounted in a small frame that attaches to the front underside of a reefer container. It runs independently of the truck's engine and provides continuous 460-volt, 3-phase power to the container's refrigeration unit.
The genset slides into a bracket on the container chassis. Most are clip-on units made to fit standard 20-foot and 40-foot ISO containers. The major genset suppliers — Thermo King, Carrier Transicold, and Shur-Lok — all produce units that bolt to the same standard mounting points.
When You Need a Genset vs Shore Power
At PortMiami and Port Everglades, most reefer stacks have shore power pedestals. The container plugs in and holds temp without burning diesel. That's the cheap option — terminals charge a daily rate for the electricity, usually around $15–25/day, far less than running a genset.
The genset becomes necessary in four situations:
- The cargo is moving to a staging yard that doesn't have shore power pedestals
- Transit time between port and warehouse exceeds a few hours in Miami summer heat
- The receiver's dock doesn't have reefer plugin capability
- A pre-pull is needed — pulling the container from the port before the receiver is ready — and the yard has no power
Pre-pulls are common in Miami drayage, especially when free time at the terminal runs short. You pull the container to your yard to avoid demurrage, but now you need to keep it cold for another 24–48 hours. Without a genset, you're gambling with the cargo temperature log.
How Gensets Work in Miami Drayage
The genset is typically rented from the chassis pool operator or the steamship line. At PortMiami, DCLI, TRAC Intermodal, and Flexi-Van all manage genset inventory. You pick up the container with the genset already attached, or you pick up the container and genset separately and connect them in the terminal yard.
Connecting a genset takes about five minutes if you've done it before. You slide the frame into the chassis bracket, connect the power cable to the reefer unit, and start the generator. Most drivers check the fuel level before leaving the terminal — running a genset dry during transit is a cargo claim waiting to happen.
One practical detail that trips up newer drivers: the genset needs to keep running while you're at the receiver's dock waiting to unload. Don't shut it down when you back in — the receiver may not have shore power available at the dock door, and an hour of waiting at ambient temp in August can push a temperature-sensitive load out of spec.
Costs, Fees, and Who Pays
Genset rental fees come from the chassis provider and get passed through the drayage invoice. Standard rates at PortMiami run $35–60 per day. That's in addition to the chassis rental itself.
The drayage carrier also absorbs fuel costs for the genset. At current diesel prices around $3.80–4.20/gallon in South Florida, a 48-hour genset run costs $75–125 in fuel depending on setpoint and ambient conditions. Most carriers bundle this into a reefer surcharge — typically $150–300 for a standard reefer drayage move requiring genset use.
Shippers sometimes balk at the genset surcharge, especially if they're used to dry cargo rates. The honest answer: you either pay for the power or you risk the cargo. The temperature log doesn't lie, and a cargo claim on a 40-foot reefer load of pharmaceuticals or produce costs far more than a $200 surcharge.
Fuel, Runtime, and Maintenance
Drivers handling reefer moves need to check genset fuel at the terminal, after delivering, and any time the container sits more than 6–8 hours at a staging location. Terminals at PortMiami have diesel fill stations, but not every yard does. The driver's responsibility ends when the container is in the receiver's possession — until then, fuel is on you.
Genset maintenance is handled by the chassis pool operator. If a genset won't start at the terminal, you swap it for another unit — don't try to repair it yourself. If a genset fails in transit, call the steamship line's emergency line immediately. Most major lines have 24-hour support for reefer emergencies.
- Check fuel level before leaving the terminal — minimum 50% preferred for Miami-area moves
- Verify the reefer unit powers up and reaches setpoint before clearing the gate
- Keep the temperature log running continuously — don't reset it between legs
- Refuel at a truck stop or yard diesel if staging overnight away from the port
- Document any genset issues in writing to the chassis pool operator before returning
Shipper Checklist for Reefer Moves
If you're the importer or freight forwarder arranging a reefer drayage move in Miami, here's what to confirm with your carrier before the container hits the terminal:
- Does your staging yard have shore power, or will you need a genset?
- What's the temperature setpoint, and is the carrier confirming it with the steamship line?
- Does your receiving dock have a reefer plug, or does the carrier need to keep the genset running at delivery?
- Is the reefer surcharge included in the quoted rate, or listed separately?
- Who gets the temperature data log — you, the carrier, or the steamship line?
- What's the carrier's protocol if the reefer alarms during transit?
Miami's summer heat compresses the timeline on cold chain decisions. A container that arrives Friday afternoon at PortMiami and can't deliver until Monday morning needs 60+ hours of cold protection. Plan that out before it becomes a 10 PM phone call about a failing genset in a Hialeah yard.