Cool boxes typically employ one of the following technologies:
Thermo-electric: The easiest, most affordable, and most energy efficient option. Here, the temperature inside the box is controlled in accordance with the temperature outside the box, and as such, it can only lower the temperature by a certain amount. This also means they don’t cool anything, but rather just keep it cold. So you need to pre-cool the contents before putting them in the box. Thermo-electric boxes have a tendency to generate a fair amount of noise when they cool, and unfortunately, they’re not that fast either.
Absorption: These cool boxes use the same type of technology found in older refrigerators, i.e., they cool the contents inside the box based on the temperature outside the box. They are typically very silent.
Compressor: These boxes employ a much more powerful cooling; so powerful in fact that they’re capable of freezing contents completely. Unfortunately, the compressor itself tends to make some noise, and it might be an issue if a user is particularly sensitive to noise.