Setting and Understanding a Refrigerated Container's Temperature Range

A refrigerated container is not a single-temperature box. The standard machine works across a wide band — from deep-frozen storage to holding goods gently above freezing — and the temperature it holds is something you set, not something fixed at the factory. This guide explains the refrigerated container temperature range, how the set point works, the difference between chilled and frozen duty, defrost, and the fact that a reefer heats as well as cools. All UK hire and purchase figures below are ex VAT, with VAT charged at 20%.

The standard range: -25 °C to +25 °C

A standard reefer operates anywhere from -25 °C to +25 °C. One unit therefore covers three very different jobs — frozen storage, chilled storage, and holding a load above freezing — without changing the machine, only the setting. A small number of super-freezer units reach -60 to -70 °C for products such as tuna or certain pharmaceuticals; these are rare and cost more to buy and to hire, so specify them only if your product genuinely needs them.

Setting the temperature

You set a target temperature on the unit’s controller and the refrigeration plant — Carrier, Thermo King, Daikin or Star Cool — works to hold it: cooling when the inside is warmer than the target and, at the warm end of the range, heating when it is colder. How tightly a given machine holds that target depends on the unit and its condition, so the sensible rule is to match the set point to your product rather than to chase a number on the display. One habit saves money above all others: choose the warmest set point your goods allow. Running frozen duty for chilled produce simply buys a higher electricity bill.

Chilled versus frozen: what it costs

Frozen duty at -18 °C works the compressor harder than chilled duty at +2 °C, and the electricity meter shows it. The gap is modest on a 20ft unit and larger in absolute terms on a 40ft high cube, which uses roughly twice the power of a 20ft whatever the set point.

These are indicative figures for a unit in reasonable condition running around the clock. Because electricity can rival the hire rate over a long term, the set point is a running-cost decision as much as a product one — our guides cover consumption and power supply in detail.

Chill-down: load cold, not warm

A reefer is built to hold goods at temperature, not to pull a warm load down quickly. How long an empty unit takes to reach its set point depends on the machine, the target and the weather, so treat any single figure with caution. In practice, give the container time to reach temperature before loading, and load product that is already at or near its target. Warm product forces the machine to work at its limit for hours and pushes consumption above the normal range.

Defrost

On frozen and cold duty, moisture from the air and from the goods freezes onto the evaporator coil over time. Left unchecked, that frost would choke airflow and blunt performance, so the unit runs periodic defrost cycles to clear it — briefly warming the coil, then returning to its set point. On modern machines this is automatic and nothing you manage day to day; it is simply one reason a real unit’s consumption varies around the figures above.

Heating: the top of the range matters

Because the band runs up to +25 °C, a reefer is not only a cold store. Set a target above freezing and the unit will heat when the surrounding air is colder than that target — keeping produce, drinks or other freeze-sensitive goods above 0 °C through winter or in an unheated warehouse. The same machine that holds -18 °C in July can hold +2 °C in January. It is a genuinely dual-purpose store, which is part of why one unit can serve so many jobs.

Matching the machine to the job

The right set point is only useful if the unit and its supply can deliver it. Full-size reefers need a three-phase 380/400 V supply through a 32 A CEE plug, drawing 5 to 12 kW while running; some small formats run on 230 V single phase. If you are buying used — observed at £4,500 to £7,500 ex VAT in the UK, against £18,995 to £22,500 ex VAT for a new one-trip unit — ask for a PTI (Pre-Trip Inspection) test under three months old, the standard check that the refrigeration unit is working properly. On the hire side, indicative long-term rates start at around £12 a day ex VAT, with minimum terms of about 90 days common, though some suppliers offer short-term hire at a higher day rate; our prices page sets out the full picture.

When you know the temperature, size and duration you need, describe your requirement once and we pass it to specialist suppliers, who contact you directly if they can meet your need.