We tested four coolers from four different manufacturers. Prices ranged from $99 to $120. All can hold about a six pack and a grocery bag full of food. Clockwise from top right: Koolatron P-65, the Coleman Power Chill 5640B, the Igloo KoolMate 3392, and the Adler/Barbour Tropicool Classic TC-32.

The last time we tested thermoelectric coolers, back in December of 1996, we spent a fair amount of space describing the history and science of the Peltier Effect, the process by which these coolers work. (In a nutshell, when you send an electrical current through the joint between two dissimilar metals, heat will pass from one metal to the other. This was discovered by M. Peltier in 1834.)

Making an icebox work is not about adding cold air to the space, but by continually removing heat from it. A Peltier Effect cooler removes heat from its insulated space by driving an electric current through those dissimilar metal partnerships (called thermocouples) set…