How to choose a cold plunge without falling for the coldest number

A cold plunge is a chiller wrapped in a tub. The number that sells it is the lowest temperature it can reach. The number that matters is the temperature it can hold, session after session, while people get in and out and the room warms and cools around it.¹

The coldest number is the easiest one to fake.

Any chiller can flash to an impressive figure on an empty tub in a cold garage. Put a person in the water, open the lid, run it twice a day for a year, and the real question changes. Not how cold can it go, but how tightly does it hold the temperature you actually set. A plunge that drifts by a few degrees between the first session and the tenth is giving each person a different session.

Four things that decide how a plunge feels.

• Held temperature. The set point it keeps, not the extreme it can touch. Ours hold within ±0.5°C of the number you set, anywhere from 2°C to 42°C.
• Recovery between users. How fast it returns to the set point after a session. From a fresh fill, a CryoLink pulls down to below 4°C in about six hours; once there, an insulated cover keeps it there and keeps the running cost down.
• Water care. Circulation, ozone disinfection and a paper-core filter keep the water clear without draining and refilling constantly. This is the difference between a plunge you use and a chore you avoid.
• The tub and the room. Filled, it weighs several hundred kilograms, so check the floor, especially above ground level. It runs off one dedicated, RCD-protected socket, not three-phase power.

The right question is not how cold it goes, but how closely it holds the number you set.

It is also a heater.

The same unit that chills to 2°C heats to 42°C. That is not a gimmick. It means the water sits ready at whatever you set rather than depending on the season, and a routine of warm then cold runs from one tub. It is a small thing that changes how often the plunge actually gets used.

What the coldest number does not tell you.

Colder is not automatically better. The evidence for cold is dose-dependent, and a steady temperature you can repeat matters more than an extreme you touch once. Some people do want the lowest setting: our ice-making option reaches 0°C, which athletes use for cold-tolerance work. Most people are better served by a temperature they can return to every day without flinching at the electricity bill. And be wary of buying on features that have not shipped yet. The daily control that matters is the one on the unit, in your hand.

Horizontal or upright.

The same chiller and the same hold come in two shapes. CryoLink H lies you back for full-body submersion, which most people find the more immersive way to plunge at home. CryoLink V stands upright and compact, a deeper seated immersion that suits a club or a room where floor space is tight. Neither is the lesser: they are two answers to where the plunge has to live.