The best cold plunge chillers for a bathtub

The submersible pump is what makes this the bathtub answer. A chiller normally needs a tub with inlet and outlet ports; a bathtub has neither. Dropping a pump into the water and running two hoses over the rim is inelegant and it works, and it is the cheapest route to a cold plunge for anyone who cannot give up floor space for a tub at all.

Six hundred watts is eleven cents an hour at full draw, comfortably mid-range here. The 79-gallon rating is a good match for a standard bathtub, which holds somewhere between 40 and 80 gallons at plunge depth.

The reusable metal mesh filter rather than disposable cartridges is a genuine running-cost detail that gets ignored because it is not electricity. Cartridge filters are a recurring purchase; a rinsable metal screen is not, and over a year that difference is larger than the difference in power draw between two chillers.

Six of eight checklist items published, including the supply voltage at 110 V, which puts this among the best-documented listings in the category. Six hundred watts is eleven cents an hour at full draw.

The specification is close to identical to the AS ColdPlunge unit elsewhere in this roundup - same 600 W, same 79-gallon rating, same 42 F floor, same 11.8 by 14.9 by 12.6 inch case - which again suggests a shared production line and a different label. Where two listings publish the same numbers, buy on price and on which kit is more complete.

The metal mesh filter is the same argument as before and it is a good one: no cartridges to replace, rinse it and put it back. Over three years that is a larger sum than most people expect.

The genuinely useful thing here is that the external filter pump arrives already connected. Anyone who has assembled a chiller loop from a box of fittings knows that this is where the leaks come from and where an afternoon goes.

Almost nothing else is published. No wattage, no dimensions, no weight, no warranty term - two of eight checklist items, the lowest count in this category, and both computed cost components score zero as a result. This is a chiller you are buying on the kit rather than on the specification, and the score says so.

The published range of 42 to 59 F is wide enough to be more of a working envelope than a floor. For most plunge protocols that envelope is fine; if you are chasing sub-40 water it is not the unit.

Direct-in-water cooling removes the entire plumbing problem: no ports, no hoses, no pump priming, no leak points. For a renter, that also removes the part of a cold plunge setup most likely to put water on a floor you do not own.

It costs you in power. At 1,200 W this is twenty-two cents an hour at full draw and, in the theoretical case of running continuously for a month, about a hundred and sixty dollars. It will not run continuously - it cycles to hold a setpoint like any refrigeration - but among the chillers here it is at the expensive end and the 280 W Pod Company unit is at the other.

The 150-gallon rating and the 39 F floor are both genuine capability. If you have a large tub and you want it properly cold rather than merely cool, this is a reasonable pairing, and the WiFi scheduling means you can have it chill overnight on a cheaper tariff if your utility has one.