What Is a Reefer Container?
A reefer container is an insulated shipping container with an integrated electric refrigeration unit mounted on the front wall. It runs on the same vapour-compression cycle as a home refrigerator but built for maritime conditions, salt spray, heavy vibration, and weeks of continuous operation. Air is drawn through the T-floor grating, cooled over an evaporator coil, and pushed back through ducts along the floor and walls. Temperature sensors at the supply and return air points feed a microprocessor controller that keeps the setpoint within roughly +/-0.5C. It plugs into the vessel's 440V/460V three-phase power supply or shore power at terminals and depots.
Temperature Guide by Commodity
The single most important operational detail in reefer logistics: the temperature setpoint. "Colder is better" is wrong and can destroy cargo.
- Bananas: 13.3C (56F). The largest reefer commodity by volume. Below about 12.8C, bananas suffer chilling injury, the peel blackens, the flesh turns mealy, and the fruit will not ripen properly. The 13.3C setpoint is the industry's most tightly held temperature.
- Fresh produce (chilled): -1C to +4C (30-40F). Leafy greens, berries, and grapes at 0-1C. Apples and pears at 0-2C. Fresh meat and poultry at 0-2C. Fresh seafood just below freezing at -1 to +1C. Dairy at +1 to +4C.
- Pharmaceuticals: +2C to +8C (36-46F). Vaccines, insulin, biologics. Continuous data logging is mandatory, a temperature deviation can justify full rejection of the shipment.
- Frozen meat and seafood: -18C to -20C (0 to -4F). Standard frozen range. The compressor runs in continuous mode.
- Deep-frozen (shrimp, tuna): -25C to -30C (-13 to -22F). Shrimp is the world's most consumed seafood and demands the coldest standard reefer settings. Ice cream travels at -25 to -29C.
The operational reality: bananas, fresh produce, frozen meat, and pharmaceuticals need different temperatures, different ventilation, and different handling. A reefer booked for +2C produce should never carry -20C frozen goods, and vice versa. The setpoint is locked based on the cargo at booking.
How the Fleet Looks
The global reefer fleet is estimated at roughly 3.7 to 3.9 million TEU as of 2024. Production in 2024 hit approximately 357,000 TEU globally, with over 90% of manufacturing concentrated in China, CIMC alone produced about 40% of global output in the first half of 2024. Production in 2025 is projected to reach 350,000+ TEU, a near-record year driven by fleet renewal and strong demand. Much of the existing fleet is 11-14 years old, and retirements are accelerating. Despite high production, equipment availability has been tight in some trade corridors due to Red Sea diversions adding roughly 10 days per voyage, disrupting container repositioning schedules. The fleet is projected to exceed 4.1 million TEU by 2027.
IoT and Digital Monitoring
Over 80% of newly built reefers in 2024 were IoT-enabled, and more than half of the total reefer fleet is now smart-equipped, up from roughly one-third the previous year. The installed base of remote tracking units on refrigerated cargo units reached 3.1 million units at the end of 2024. Major carriers are all-in: Maersk's entire 360,000-unit reefer fleet has real-time tracking. Hapag-Lloyd has equipped its full reefer fleet and is retrofitting most of its dry fleet.
These IoT systems transmit temperature, humidity, door-open status, and GPS location via cellular or satellite. Cargo owners can watch individual reefer conditions on a dashboard and receive alerts if any parameter drifts outside the acceptable range. The practical result: IoT-enabled reefers experience measurably fewer cargo claims compared to non-connected units, and early unit-failure prediction from machine learning models allows preventative maintenance before cargo is lost.
Frequently Asked Questions
What temperature range can a reefer container maintain?
Standard reefers maintain roughly -30C to +25C. The setpoint depends entirely on the cargo. Bananas need a precise 13.3C; frozen meat travels at -18C to -20C; deep-frozen seafood at -25C to -30C; chilled produce and pharmaceuticals at +2C to +8C. Controlled atmosphere reefers add oxygen and CO2 regulation for fresh produce, extending shelf life by weeks.
How does a reefer container get power during sea transport?
Reefer containers plug into the vessel's electrical system via dedicated reefer sockets on deck or in purpose-built holds. Most container ships supply 440V/460V three-phase power. Each unit draws roughly 5-7 kW on average, varying with ambient temperature and setpoint. Terminals and depots provide shore-power plug-in stations for pre-cooling and monitoring before loading.