The two look almost identical from the outside: the same steel box, the same corner castings, often the same white paint. The difference sits behind the front wall. An insulated container is a well-lagged box with no cooling unit at all; a refrigerated container — a reefer — carries an active refrigeration unit that actually makes cold. Choosing between them comes down to a single question: do you need to hold a temperature, or simply slow one down?
What actually separates the two
An insulated container has thick insulated panels on its walls, floor and ceiling and well-sealed doors. It passively resists heat exchange, so it keeps contents cool and frost-free for a while — but with no machinery, the interior slowly drifts towards the outside temperature. No power, no plug, nothing to run.
A reefer has the same insulation plus a refrigeration unit — Carrier, Thermo King, Daikin or Star Cool — that draws three-phase power and holds a chosen setpoint, anywhere from -25°C to +25°C as standard. Because the reefer keeps cold while the insulated box only delays warming, an insulated unit costs 30-50% less than an equivalent working reefer.
When an insulated container is enough
An insulated box does the job when absolute temperature is not the point:
- Dry, temperature-sensitive storage — goods that must stay cool and dry, but not chilled to a number.
- Passive frost protection — keeping paint, liquids or produce above freezing through winter without running a chiller.
- Buffering ambient swings — a store where the enemy is the daily temperature swing rather than heat itself.
It is the wrong tool the moment you need a guaranteed chilled or frozen setpoint. Holding +2°C for perishables, or -18°C for frozen stock, needs a working reefer with power.
Insulated vs refrigerated at a glance
| Insulated container | Refrigerated container (reefer) | |
|---|---|---|
| Cooling unit | None | Active refrigeration unit |
| Holds a setpoint | No — drifts to ambient | Yes, -25°C to +25°C standard |
| Power needed | None | Three-phase 380/400 V, 32 A CEE |
| Running electricity | None | 70-170 kWh/day (UK, by format) |
| Typical used price, ex VAT | ~£2,250-5,250 | £4,500-7,500 |
| Best for | Dry sensitive storage, frost protection | Chilled or frozen storage and transport |
The insulated figure above simply applies the 30-50% discount to the UK used-reefer range — treat it as indicative rather than a quote.
Running costs and interior space
Running electricity is the biggest ongoing gap. A working reefer draws roughly 70-170 kWh a day depending on size; an insulated container draws nothing once it is sited. Over months of storage that difference dwarfs the price gap on the box itself.
Both types lose interior space to their insulation, and a refrigerated or insulated unit is noticeably smaller inside than a dry container of the same size, because the walls, floor and ceiling are thicker. A 40ft high-cube reefer gives about 2.55 m of interior height; a 20ft works out around 5.44 × 2.29 × 2.27 m inside. Insulated boxes carry the same insulation, so expect the same reduced internal dimensions — worth allowing for when you plan pallet layouts.
The “insulated only” reefer
A reefer whose unit has failed or been removed is, in practice, an insulated container — and it is often sold or hired as one. That is a legitimate, cheaper route if you only need passive insulation. Just be clear on what you are buying: labels such as “non-operational”, “unit removed” or “insulated only” mean there is no cooling and no setpoint, however smart the box looks. Ask before you commit rather than after.
One regulatory caveat
If goods move, note that ATP certification covers refrigerated transport, not a container standing still as a store — a static insulated or refrigerated unit used purely for storage is a separate question from ATP. Food-storage rules such as HACCP vary by country and even by local authority, so check the requirements with the relevant body before you commit to either option.
Which should you choose?
If you need to guarantee a chilled or frozen temperature, go for a working reefer: used units run £4,500-7,500 ex VAT, new one-trip boxes £18,995-22,500 ex VAT, and long-term hire starts around £12/day (a 90-day minimum is common, though some suppliers offer shorter terms). If you only need to keep goods cool, dry and frost-free, an insulated box does the same passive job for far less.
Compare current UK figures on our prices page, browse containers for sale, or read the rest of our reefer guides. When you know what you need, tell us about your project — we pass your enquiry to specialist reefer suppliers who get back to you directly if they can meet your needs.
Frequently asked questions
Is an insulated container the same as a refrigerated one?
No. An insulated container is a well-lagged steel box with no cooling unit — it slows heat exchange but drifts towards ambient temperature. A refrigerated container adds an active refrigeration unit that holds a setpoint, typically between -25°C and +25°C as standard. If you need a guaranteed chilled or frozen temperature you need the reefer; for passive protection the insulated box is enough.
How much cheaper is an insulated container?
An insulated, non-operational unit typically costs 30-50% less than an equivalent working reefer, because it carries no refrigeration machinery. In UK terms that puts a used insulated box broadly in the £2,250-5,250 ex VAT bracket, against £4,500-7,500 for a working used reefer. It also costs nothing to run, whereas a reefer draws electricity continuously.
What can I store in an insulated container without power?
An insulated container suits dry, temperature-sensitive goods and passive frost protection — keeping paint, liquids or produce above freezing in winter, or buffering contents against ambient swings. It cannot hold a chilled or frozen setpoint, so it is unsuitable for anything that must stay reliably cold. For that you need a powered reefer with a working refrigeration unit.
Can I use a non-operational reefer as an insulated box?
Yes. A reefer whose unit has failed or been removed works exactly as an insulated container, and is often sold or hired that way at a lower price. Just confirm the listing states non-operational, unit removed or insulated only, so you know there is no cooling and no setpoint, however new the box may look.