A compressor cools below ambient; a thermoelectric box only below it a little · review

DOMETIC TropiCool TCX 21, 21 litres, cools 27 °C below ambient and heats to +65 °C review

A 21 litre box that both cools to 27 °C below ambient and heats to +65 °C, with battery protection against deep discharge and reverse polarity.

By Jean-Benoit Buisson

The bottom line The only box here that heats, and the only one honest enough to state its cooling relative to ambient rather than as an absolute. That honesty also reveals the limitation: on a hot day it is a cool box rather than a fridge.

A 21 litre box that works in both directions.

The phrase that tells you the technology

“Up to 27 °C below ambient temperature.” That is how a thermoelectric box is specified, because it cools by a fixed margin rather than to a set point. In a 20 °C car it reaches −7 °C; in a 35 °C car, 8 °C.

Every other box in this family quotes an absolute minimum, which is how a compressor works. This listing is describing something different and describing it correctly.

What it adds

Heating to +65 °C. Nothing else here heats. For a journey with food as well as drink, that is the whole argument.

The protection, named

Deep discharge protection for the vehicle battery, and reverse polarity protection. Named rather than implied — though the voltage thresholds that define the cut-off are not published, as on every box in this family that names one.

And the figure nobody publishes

Daily consumption.

Availability

German, French, Italian and Spanish Amazon stores quoted 179 € to 234 € when this page was compiled.

American and British Amazon stores returned nothing at all, so the buy button there runs a search instead of landing on an empty page.

These figures are what Keepa reported on the day this page was last updated. Availability and pricing move without notice.

Prices quoted in this text were read on 16 September 2026. The live price is at the top of the page.

What it gets right, and what it leaves out

Strengths

It heats as well as cools, to +65 °C, which nothing else in this family does
Battery protection is named, including reverse polarity
Three supply voltages — 12, 24 and 230 V

Compromises

Cooling is stated relative to ambient, so on a 35 °C day the box reaches only 8 °C
No thresholds for the battery protection it names
No daily consumption and no noise figure

Specifications

Temperature range	Cools up to 27 °C below ambient and heats to +65 °C, first bullet — expressed relative to ambient rather than absolutely
Daily consumption at stated conditions	Nowhere in the listing
Compressor type	Not a compressor — the cooling is expressed relative to ambient, which describes a thermoelectric system
Battery protection levels	Protection against deep discharge of the vehicle battery and reverse polarity, third bullet; no voltage thresholds are published
Insulation	Nowhere in the listing
Capacity	21 litres, from the title
Noise	Nowhere in the listing
Amazon reference	B07QR5QHRH (same reference on 4 Amazon marketplaces)
EAN	4015704271454

Questions owners ask about this one

Why does “27 °C below ambient” matter so much?

Because it is not an absolute temperature. In a 20 °C car the box reaches −7 °C; in a 35 °C car it reaches 8 °C. A compressor box holds its set point regardless of ambient. That is the fundamental difference between the two technologies and this listing states it correctly.

What does heating to +65 °C do?

Keeps food warm on a journey. No other box in this family offers it, and it is what distinguishes a cool-and-warm box from a cool box.