Cold plunge chillers explained: how they work and how to size one
How cold plunge chillers work, how to size one for your tub (1/3 HP to 1.5 HP), what to check before buying, and typical UK prices.
Published , updated .
The tub is the cheap part. The chiller decides whether the water is 4C in July, whether it stays clean between changes, and what the whole setup costs to run. The chiller catalogue lists every unit sold in the UK.
What a chiller does
A cold plunge chiller is a small water-cooled refrigeration unit. A pump draws water from the tub, passes it through a filter and a cooling coil, and returns it. Many units sold in the UK also include UV or ozone sanitisation, and more of them heat as well as cool than a year ago. Set the target temperature once and the chiller cycles on and off to hold it.
Sizing
Home chillers sold in the UK run from 1/3 HP to 1.5 HP. The right size depends on tub volume, insulation, whether the tub is covered, where it lives (garage, garden, indoors), and your target temperature.
| Chiller rating | Suits | UK price in our catalogue |
|---|---|---|
| 1/3 HP (about 280 W draw) | Small portable tubs to about 350 L, indoors or shaded, covered | £499 (Pod Chiller) to £549.99 (Polar Recovery Cube) |
| 1/2 HP (about 1,200 W of cooling) | 300-500 L insulated tubs, outdoors with a cover, 3-8C all year | £599 (Kove Core) to £675 (Keico Classic) |
| 0.8 to 1.5 HP (2,300-3,500 W of cooling) | Large or uninsulated tubs, two people, heavy daily use, fast pull-down; most also heat | £1,185 to £1,950 |
Heat pumps (Poolex and Wedge, sold by Urban Ice Tribe) are rated in kW of heating rather than horsepower and cost £645 to £2,880. For your own tub, the chiller sizing calculator works it out from volume, insulation and where the tub lives.
Undersized chillers run continuously, cost more in electricity, and never reach target in warm weather. Oversizing costs more up front and little in running costs. When in doubt, go one size up.
What to check before buying
- Minimum temperature. Some unbranded imports stop at 5 to 8C; look for 3C or lower.
- Filtration and sanitisation. A filter cartridge plus UV or ozone means fewer water changes.
- Noise. Fewer than half the chillers we list state a figure; most of those that do sit between 38 and 55 dB at one metre. Where it sits matters if it runs at night.
- Heating. Dual-mode units (cool and heat) cost more but cover contrast therapy.
- Fittings. Check hose diameters and whether the tub has proper in and out ports.
- Warranty and UK support. Chillers are the component that fails. A UK-based warranty is worth paying for.