To choose a home cold plunge, start with how cold you need the water and how hard the chiller will have to work to get it there in your space. Then check filtration, insulation, size, weather rating, power supply and after-sales support. A well-matched plunge holds a steady temperature with very little effort from you, while a poorly matched one means slow cool-downs, cloudy water and a tub you stop using.
For the wider picture, including setup and costs, see our cold plunge buying guide.
Start with how you will actually use it
Before comparing specifications, decide where it will live (garden, garage or indoors), who will use it, how often, and whether you want warm water too. A tall adult needs more internal length and depth. Daily use makes temperature holding and long-lasting water quality more important. Heating is useful if you want a warm soak or to alternate hot and cold.
Chiller power: the engine of the plunge
The chiller decides how quickly the water gets cold and how well it stays cold on a warm day. Manufacturers describe chillers in two different ways, which causes a lot of confusion. Horsepower (HP) usually describes the size of the compressor motor, while cooling capacity in kilowatts (kW) describes how much heat the chiller can remove from the water. Cooling capacity is the more useful figure when you are comparing performance.
Look for a quoted cool-down time with the conditions stated: the volume of water, the start and finish temperatures and the room or outdoor (ambient) temperature. A figure without those details is hard to compare. Our guide to cold plunge chillers explains HP, kW and ambient temperature in more depth.
Lowest temperature: think headroom, not bragging rights
You will usually use a plunge warmer than its minimum, especially when starting out. The lowest rated temperature still matters because it shows how much headroom the chiller has to hold your chosen temperature on a hot afternoon or in a warm garage.
Filtration and sanitation
Unlike a bath, a cold plunge is meant to stay filled for weeks, so the water needs to be kept clean while you are not using it. Check three things:
- Filter fineness. Filters are rated in microns. A lower number catches finer particles such as hair, skin flakes and dust.
- Stages and sanitation. Some systems use more than one stage of filtration and add ozone, which is used alongside filtration to help keep water fresher between changes.
- Running costs of upkeep. Find out how often cartridges need replacing and what they cost, and how easy the filter housing is to reach.
Filtration does not replace basic care such as showering first, using the cover and changing the water regularly. Our water maintenance page covers the routine.
Insulation and cover
Any heat the water gains from the air, ground or sun is heat the chiller must remove. Insulated walls and a well-fitting insulated cover reduce that gain, keep debris out and help keep running costs down. If a cover is sold separately, add it to the price before you compare models.
Size, capacity and weight
You want enough internal length to sit with your legs out or slightly bent, and enough depth for the water to reach your shoulders when seated. Allow room to step in and out, reach the chiller and get the delivery in. Larger volumes take longer to cool and use more water at each change. Weight matters too, because a litre of water weighs about a kilogram. A 700 litre tub holds roughly 700kg of water before you add the tub and a person. On a ground floor slab that is rarely a problem, but for an upper floor or a raised deck, ask a structural engineer before you buy.
Indoor or outdoor: understand the IP rating
An IP (ingress protection) rating tells you how well an electrical enclosure resists water. Under the international IP code, IPX4 means water splashed from any direction should have no harmful effect, and IPX5 means water projected from a nozzle from any direction should have no harmful effect. The X simply means the dust rating is not specified. Outdoors, you also need a level base, shade where possible, drainage for water changes and a plan for frost.
Power supply
A standard UK 13A socket can supply roughly 3kW, so check the rated power of the chiller and any heater against your supply. Many plunges ask for a dedicated socket that is not shared with other high-power appliances. Electrical Safety First advises using residual current device (RCD) protection with outdoor electrical equipment and using only weather-resistant, outdoor-rated leads outside. If you need a new outdoor socket or circuit, use a registered electrician. Our article on cold plunge running costs shows how rated power translates into electricity bills.
Warranty, returns and support
A cold plunge combines water, refrigeration and electronics, so check the warranty length and cover, the availability of filters and parts, the returns window and how you reach support.
Every ThermoX plunge comes with a 1-year warranty, free UK delivery and a 30-day returns window for unused items in their original condition. Our UK-based team is at hello@thermoxrecovery.com.
How the ThermoX range compares
If you are weighing up options, here is a brief summary of our cold plunges and our bath chiller:
| Model | Type | Lowest temperature | Heating | Cooling | Filtration | Water rating | Price |
|---|---|---|---|---|---|---|---|
| ThermoX Core | Compact tub with chiller | 5°C | No | 0.3HP chiller | 20 micron | IPX4 | £1,495 |
| ThermoX Pro | 700L tub with external chiller | 3°C | Yes, to 40°C | 1HP chiller | Dual-stage 20 micron plus ozone | IPX5 | £3,495 |
| ThermoX Elite | All-in-one with integrated chiller | Holds as low as 3°C | Yes, to 40°C | 3kW cooling | Dual-stage 20 micron plus ozone | IPX5 | £4,995 |
| ThermoX Drop | Chiller for the bath you own | 3°C | Range 3 to 25°C | 3.5kW cooling | 20 micron plus ozone | Not specified | £1,995 |
The Core, Pro and Elite are suitable for indoor or outdoor use. If you are deciding between tub constructions more generally, read inflatable vs rigid cold plunge tubs.
A quick safety note
Cold water puts real stress on the body. The RNLI describes cold water shock, an involuntary gasp and rapid breathing that can follow sudden immersion in water below 15°C, and the British Heart Foundation notes that cold immersion can raise heart rate and blood pressure. Speak to your GP first if you have a heart condition, high or low blood pressure, are pregnant or have any other medical condition. Never plunge after drinking alcohol, avoid plunging alone, and start warmer and shorter than you think you need. Our beginner guide covers your first sessions.
Frequently asked questions
What is the most important feature in a home cold plunge?
The chiller, because it decides how quickly the water cools and how well it holds temperature in warm weather. Compare cooling capacity in kW and cool-down times quoted with the water volume and ambient temperature stated.
Do I need a cold plunge that heats as well as cools?
Not necessarily. Heating is useful if you want a warm soak or plan to alternate hot and cold in one tub, but if you only want cold water a cooling-only unit can be simpler and cheaper.
Can I put a cold plunge outdoors in the UK?
Yes, if the unit is rated for outdoor use. Check its IP water rating, use a level base and an RCD-protected outdoor supply, keep the cover on, and plan for frost and drainage.
How big should a cold plunge be?
Big enough to sit with your legs out or slightly bent and the water at shoulder height. Remember that larger tubs take longer to cool, use more water at each change and weigh more when full.