What Is a Reefer Container? How Refrigerated Containers Work

A reefer container is a shipping container with a built-in refrigeration unit that holds the cargo at a set temperature from origin to destination. “Reefer” is maritime shorthand for refrigerated. The same box plugs into a ship, a terminal or a truck and keeps the load cold the whole way, which is why almost all frozen and chilled cargo moves inside one.

If you need to buy or rent a unit rather than read the theory, jump to our reefer containers page for stock, sizes and a quote.

How a reefer container works

A reefer is not just an insulated box. It runs an active refrigeration cycle, the same vapour-compression principle as a domestic fridge, only built for cargo:

1. The compressor pressurises the refrigerant gas.
2. The condenser releases heat and turns the gas to liquid.
3. An expansion valve drops the pressure and temperature.
4. The evaporator absorbs heat from inside the container.

Two design features make it work in practice. The walls are packed with 65 to 100 mm of polyurethane foam so outside heat stays out. And the floor is a T-bar aluminium grating: chilled air is pushed up from the floor, travels through and around the cargo, then returns to the unit. Loading to the floor and keeping the T-bar channels clear is what lets the air circulate evenly.

A reefer holds temperature, it does not cool warm cargo

This is the point most people get wrong. A reefer maintains the temperature you load at; it is not designed to pull warm goods down to freezing. Cargo has to be pre-cooled to its target temperature before it goes in. Load warm produce into a reefer set to +2 C and the unit will struggle for hours while the top of the load spoils. Pre-cooling is the single biggest factor in whether a shipment arrives in good condition.

(If you genuinely need to freeze warm product, that is a blast freezer container, a different unit.)

Temperature range and cargo

Standard reefers hold cargo-space temperatures from about -30 to +30 C, typically within half a degree of the set point. Specialised super freezer units reach -60 to -70 C for sashimi-grade tuna and medical samples. Common set points:

Cargo	Typical temperature
Ice cream, deep-frozen seafood	-25 to -18 C
Frozen meat and poultry	-18 C
Dairy (milk, cheese, yogurt)	0 to +4 C
Fresh produce (apples, lettuce)	0 to +13 C
Pharmaceuticals and vaccines	+2 to +8 C
Cut flowers	+2 to +4 C
Bananas and ripening fruit	+12 to +14 C

Humidity, ventilation and atmosphere control

Temperature is only part of the job. Modern reefers also manage the air around the cargo:

• Ventilation: fresh vents let out the CO2 and ethylene that fruit and vegetables give off as they respire. Frozen loads keep the vents closed.
• Humidity: most units hold 60 to 85 percent relative humidity, and some newer models go down to around 50 percent for drier cargo.
• Controlled atmosphere: higher-spec units adjust oxygen and CO2 levels to slow ripening, which can extend the shelf life of produce on long voyages.

Reefer container dimensions and specifications

Reefers have less internal space than dry boxes because the refrigeration unit and thick insulation take up room. Figures below are typical; confirm against the specific unit before loading.

Specification	20ft Reefer	40ft HC Reefer
ISO type code	22R1	45R1
External (L x W x H)	6.058 x 2.438 x 2.591 m	12.192 x 2.438 x 2.896 m
Internal volume	~28 m3	~67 m3
Tare weight	~3,050 kg	~4,600 kg
Max payload	~27,400 kg	~29,000 kg
Temperature range	-30 to +30 C	-30 to +30 C

Reefer vs dry container

Feature	Dry container	Reefer container
Temperature control	None	-30 to +30 C
Insulation	Minimal	Polyurethane 65 to 100 mm
Power	Not required	380 to 460 V, 3-phase
Flooring	Flat plywood	T-bar aluminium
Internal volume	Larger	About 20% less
Tare weight	Lighter	1,500 to 2,000 kg heavier
Cost	Lower	Higher

Types of reefer container

• Standard reefer: -30 to +30 C, the everyday unit.
• High Cube reefer: one foot taller, about 13 percent more volume, the most common 40ft type.
• Super freezer: -60 to -70 C using cascade refrigeration.
• Blast freezer: actively freezes warm cargo.
• Multi-zone / dual-temperature: a partition creates two set points in one box.
• Non-operating reefer (NOR): an insulated reefer run with the unit switched off, used as a normal dry box to reposition equipment cheaply. Handy when you want an insulated box but do not need cooling.

Power requirements

A standard reefer runs on three-phase power, 380 to 460 V, drawing roughly 4 to 8 kW at steady state. Super freezers pull more. Power comes from one of three sources:

• Vessel reefer plugs while at sea.
• Shore power racks at the terminal or on site.
• A clip-on or underslung diesel generator (genset) during road transport.

Monitoring and pre-trip inspection

Every unit logs the supply and return air temperatures, defrost cycles and set-point changes, which matters for food safety and audited pharma cold chains. Before each trip the reefer goes through a Pre-Trip Inspection (PTI): the technician checks the compressor, sensors, gaskets, defrost, refrigerant and data logger. Skipping the PTI is how a cold chain fails mid-voyage.

Using a reefer as cold storage

A reefer does not have to move to be useful. Plugged into a suitable power supply, it works as static cold storage for restaurants, supermarkets, hospitals, event caterers and food processors. It is a fast, portable way to add chilled or frozen capacity without building a cold room. This is one of the more common reasons Singapore businesses buy or rent a reefer outright.

Reefer container costs

Prices vary with size, condition, age of the refrigeration unit and the market, so treat these as a rough guide only:

Unit	New (approx)	Used (approx)
20ft reefer	USD 18,000 to 30,000	USD 8,000 to 15,000
40ft High Cube	USD 25,000 to 45,000	USD 12,000 to 22,000
Super freezer (40ft)	USD 50,000 to 80,000	USD 30,000 to 50,000

Rental runs roughly USD 100 to 250 a day for a 20ft and USD 150 to 350 for a 40ft HC, before PTI, plug-in, genset and fuel charges. For current Singapore pricing, ask us for a quote.

Advantages and trade-offs

Reefers give precise temperature control, run across ship, rail and road on the same box, log their own temperature data, and can extend shelf life with controlled atmosphere. The trade-offs are real too: they cost more than dry boxes, carry a freight surcharge, depend on continuous power, hold about 20 percent less cargo, and need a qualified technician to service. For most temperature-sensitive cargo, there is simply no substitute.

Buying or renting a reefer in Singapore

As a container supplier in Singapore, INFINEX supplies reefer containers for sale and rental:

• 20ft and 40ft High Cube units in new and quality used condition.
• Sale, short and long term rental, and one-way hire.
• Units pre-tripped and temperature-tested before release, with genset and shore-power guidance.
• Full range under one supplier, including ISO standard containers, special containers and used containers.

See the reefer containers page for specs and stock, or contact us for a quote.

Frequently asked questions

What does “reefer” mean in shipping?

It is maritime slang for refrigerated. A reefer container is any intermodal container with a built-in refrigeration unit for temperature-sensitive cargo.

Can a reefer container freeze warm cargo?

No. A standard reefer maintains the temperature you load at, so cargo must be pre-cooled first. Freezing warm product is a job for a blast freezer container.

How long can a reefer hold temperature without power?

A well-insulated, fully loaded frozen reefer typically holds a safe temperature for about 4 to 8 hours, depending on the ambient conditions. Chilled loads have less buffer.

Does a reefer need three-phase power?

Yes. It runs on 380 to 460 V three-phase power from shore, a vessel, or a clip-on diesel generator during road transport.

Can I use a reefer for stationary cold storage?

Yes. With a suitable power connection a reefer works as portable cold storage for food businesses, events and healthcare. It is a common alternative to building a cold room.

How long does a reefer container last?

Around 12 to 15 years in active shipping service. The refrigeration unit may need a major overhaul after 8 to 10 years, so check its age and compressor hours on a used unit.

Should I buy a new or used reefer?

New units suit long leases and sensitive cargo like pharma. Quality used reefers are cost-effective, especially for stationary cold storage. On any used unit, inspect the refrigeration age, insulation and door gaskets.