A 12V cool box is the budget alternative to a compressor fridge. It costs a fraction of the price (£30-100 vs £250-800), uses more power, and keeps things cool rather than cold. For weekenders and budget builds, it's a legitimate option.
This guide covers the best 12V cool boxes available in the UK, their power consumption, and when a cool box makes more sense than a fridge.
Cool Box vs Compressor Fridge
| Feature | 12V Cool Box (Peltier) | Compressor Fridge |
|---|---|---|
| Price | £30-100 | £250-800 |
| Temperature | 15-20°C below ambient | -18°C to +10°C (you choose) |
| Power use (continuous) | 40-60W | 5-15W (average) |
| Power use (daily) | 40-60Ah (runs 100%) | 8-25Ah (cycles 25-40%) |
| Cools below freezing | No | Yes |
| Battery-friendly | No (high draw, continuous) | Yes (cycles, low average draw) |
| Lifespan | 2-4 years | 10-15 years |
| Cooling speed | 30-60 min | 10-20 min |
The key difference: A compressor fridge cycles — it runs, cools, rests, runs again. A Peltier cool box runs continuously. This makes the cool box a power hog (40-60Ah/day vs a compressor's 8-25Ah/day).
How a Peltier Cool Box Works
Peltier cool boxes use the Peltier effect — passing electricity through two different conductors creates a temperature difference. One side gets cold, the other gets hot. The hot side needs to be ventilated, which is why cool boxes have a fan.
The limitation: The temperature difference between the cold side and the hot side is limited to 15-20°C. If it's 25°C inside your van, the cool box will get to 5-10°C. If it's 35°C inside your van (summer, parked in the sun), the cool box will only get to 15-20°C — not cold enough to keep milk safe.
Best 12V Cool Boxes (UK)
WAECO CoolFun 12V Cool Box (CF-30)
- Price: £70-100
- Capacity: 30L
- Power: 48W
- Features: 12V/240V dual, carry handle, reversible lid
- UK supplier: Amazon UK, Go Outdoors
Best for: Quality-conscious buyers who want a proper cool box. WAECO is the same company that makes Dometic fridges — their Peltier cool boxes are better built than the cheap alternatives. The dual-voltage (12V car + 240V mains) is useful for cooling at home before a trip.
Issues: The fan is noisy (audible inside the van at night). The 12V cable has a cigarette lighter plug that gets hot with sustained use.
Alpicool 12V Portable Cool Box (P20)
- Price: £40-60
- Capacity: 20L
- Power: 42W
- Features: 12V only, low-noise fan, cup holder lid
- UK supplier: Amazon UK
Best for: Budget buyers. Alpicool's Peltier cool box is the cheapest option from a decent brand. The 20L capacity is enough for a weekend's food for one person. The low-noise fan is quieter than most.
Issues: The 20L capacity is small — you'll outgrow it if you van life for more than a weekend. The cooling element stops working if the cool box is tilted more than 30° while running (the Peltier element needs to be horizontal).
Mobicool M30
- Price: £50-80
- Capacity: 30L
- Power: 45W
- Features: 12V/240V, bottle opener, can dispenser
- UK supplier: Amazon UK, Halfords
Best for: General use. The Mobicool M30 is the standard mid-range cool box. It's the one you see at Halfords. The 30L capacity holds a 2L milk carton, a pack of cheese, some vegetables, and a few drinks. The bottle opener on the front is an ice-breaker at campsites.
Issues: The thermoelectric element burns out after 2-3 years of regular use (common with all Peltier cool boxes — they have a limited lifespan). Not as well insulated as the WAECO.
Arctic 12V Cool Box (35L)
- Price: £60-90
- Capacity: 35L
- Power: 50W
- Features: 12V/240V, removable shelf, cup holders
- UK supplier: Amazon UK
Best for: Larger capacity. The 35L holds enough for 2 people for a long weekend. The removable shelf lets you separate food from drinks.
Issues: It's large for a Peltier cool box — a larger volume means the Peltier element has to work harder and the internal temperature is less consistent (25°C at the top, 12°C at the bottom, 5°C next to the cooling plate). Heavy when full (8-10kg).
Power Reality
A Peltier cool box running continuously draws about 40-60W = 3.3-5A.
What this means for your battery:
| Battery | Capacity | Max Run Time | Realistic Run Time (with other uses) |
|---|---|---|---|
| 75Ah lead-acid (usable: 37Ah) | 37Ah / 4A = 9.25h | Not enough — your battery is dead in 9 hours | |
| 100Ah lead-acid (usable: 50Ah) | 50Ah / 4A = 12.5h | 8-10h (you need the battery for lights etc) | |
| 100Ah LiFePO4 (usable: 80Ah) | 80Ah / 4A = 20h | 14-16h (must recharge daily) | |
| 200Ah LiFePO4 (usable: 160Ah) | 160Ah / 4A = 40h | 30-36h (can do 2 nights) |
The problem: A Peltier cool box is a 24-hour device. It doesn't cycle. It runs all day and all night. Even a 100Ah LiFePO4 can only run it for 14-16 hours before the battery is below 50%.
With solar:
- 200W solar on a summer day: generates 50-70Ah
- Cool box uses 40-60Ah
- You have 10-30Ah surplus for other uses
In winter:
- 200W solar generates 10-20Ah
- Cool box uses 40-60Ah
- You have a 20-50Ah deficit every day
Verdict: A Peltier cool box is workable in summer with 200W+ solar. In winter, it will drain your battery overnight unless you run your engine for 2-3 hours a day.
Making a Cool Box Work
Pre-Cool
The most effective way to reduce power use is to have everything cold before it goes in the cool box. Pre-cool the cool box at home on mains power (run it for 3-4 hours before you pack). Pre-chill all food and drinks in your home fridge. A cool box full of cold items uses less power than one full of warm items (the Peltier element doesn't have to work as hard).
Use Ice Packs
Add 2-3 reusable ice packs (the blue gel type, £3-5 each) to the cool box. They absorb heat from the contents during the day and reduce the temperature variation when the cool box is opened. They also reduce the load on the Peltier element.
The ice pack trick: Freeze them at home and swap them out every 2-3 days when you're at a campsite/hook-up.
Insulate
Add a layer of closed-cell foam (Reflectix from Screwfix, £5-8) around the outside of the cool box. This reduces heat gain and lowers the cool box's duty cycle. Wrap it like a pizza delivery bag — the Lidl/Thermal Cool Bag (£3.99) cut to shape works well.
Use a Timer
Connect the cool box via a 12V timer switch (Amazon, £10). Run it for 30 minutes on, 30 minutes off. This extends battery life by 40-50%. The temperature inside will fluctuate by 3-5°C but most food is fine with that.
When to Upgrade from Cool Box to Fridge
A cool box is a temporary solution. You'll know it's time to upgrade when:
- You can't keep milk fresh for more than 1 day in summer
- Your battery is below 50% every morning
- You're tired of buying ice packs every week
- You find yourself avoiding buying fresh food because you can't store it
A good upgrade path: use a cool box for the first 3-6 months of van life, save the budget for a proper compressor fridge, and move the cool box to backup duty.
