It may come as a surprise to learn that passive coolboxes have made a comeback, when powered coolboxes are now more affordable and more widely available than they have ever been. But perhaps when you realise how far passive coolbox technology has come and the fact that they often keep items cooler than powered products, and that they can be used off-grid, they’re definitely accessories worth considering for your caravan holidays. Once you unplug a powered coolbox, the temperature inside can rise quite quickly – not ideal for a picnic on a hot, summer’s day. And as they do not have ventilation grilles (as you will find on fridges or powered coolboxes), you can store passive coolboxes wherever is most convenient, although not in direct sunlight.

All of which explains why the Practical Caravan review team conducted a passive coolbox group test. Every product went through the same series of tests to ensure they were assessed fairly and on the same terms. Their thermal capabilities are of course very important, so they were all opened and left until they reached an ambient temperature of 25˚C. The coolboxes were then loaded with ice chilled to -12˚C (each box received ice totalling 5% of its capacity), closed and put in a room kept at 27˚C for eight hours, their internal temperatures checked frequently during this time. A pretty rigorous test.

What other factors did we take into account? Price, value for money and build quality are important, as is the coolbox’s depth and ability to store bottles upright. Premium brands often fit proper seals to prevent warm air from displacing cool air inside the box. Large feet are also useful as they leave a gap for cool air to pass between the base of the box and the warm ground on which it is sitting. Some coolboxes have padlocks, so alcoholic beverages can be kept away from kids and some have drainage bungs, which let you remove water without exposing the box’s interior to warm air.

In this instance we were reviewing the 26-litre Igloo Island Breeze rolling cooler, which retails at an affordable £48. This is the standard Island Breeze with wheels, a long retractable handle and a higher price. But, arguably, it’s worth the extra cash. A 26-litre box full of food or drink is not light, so the wheels and handle make moving this a doddle. In addition, two grabhandles are moulded into the body, so the box can be carried if the terrain gets rough, which is a thoughtful touch. The finish and build quality are also impressive, while we easily got our two-litre bottle in this passive coolbox and shut the lid.

This pull-along coolbox received a three-star rating from the expert Practical Caravan review team, while another item from the same manufacturer, the 28-litre Sportsman, scored four out of five. The considerably more pricey, 45-litre Techniice Signature was also awarded four stars in the same product group test, as was the £100 Icey-Tek Cube Box. However the Editor’s choice was the Waeco Cool-Ice, which will set you back £115 and got a five-star rating. The product from Argos received a one-star rating.