A cold plunge tub is simple in principle: an insulated tub of cold water. The differences between models are in how cold they get, how cleanly they keep the water, how much they weigh when full and what they cost to run. This guide covers each in turn.
1. Chiller or no chiller
| With a chiller | Without a chiller | |
|---|---|---|
| How it gets cold | A chiller unit cools and usually filters the water | Cold tap water, plus ice if you want it colder |
| Temperature | Holds a set temperature; the lowest it reaches depends on the model and the weather | UK tap water varies with the season: cold in winter, often 15°C or more in late summer |
| Water care | Circulation and filtration help keep water clean for longer | Water needs changing more often |
| Running cost | Electricity, typically about £25–£50 a month (see the running-cost guide) | The cost of water and ice |
| Best for | Regular, year-round use at a steady temperature | Occasional use, or winter-only use outdoors |
Some chillers can also heat the water, which is useful if you want a year-round tub. Our chiller guide explains the specifications, water care and noise.
2. Tub types
- Insulated hard tubs (fibreglass, acrylic or composite): rigid, good insulation, a tidy finish and usually a fitted lid. Most chiller packages use this type.
- Stainless steel: very durable and easy to clean. Often a premium option.
- Timber barrel tubs: traditional Nordic look, sitting well beside a barrel sauna. Check the insulation and the lid if you plan to use a chiller.
- Inflatable or soft tubs: cheap and portable, but they insulate less well, so a chiller works harder. Better for trying cold plunging than for daily use.
3. Size and weight
- Fit: check the internal length and depth against the tallest user. You want to sit with water to your shoulders.
- Weight: water weighs about 1 kg per litre, so a 500-litre tub holds about half a tonne of water before the tub and the person. Stand it on a firm, level base that can take the full load, such as a concrete slab or suitable paving. Check the load rating before putting a filled tub on decking, a balcony or an upper floor. Our base guide shows the weight maths.
- Space around the chiller: chillers need airflow, so leave the gap the manufacturer specifies.
4. Power
Most chillers run from a standard 13A socket, but check the product page. Outdoor sockets must be weatherproof and RCD-protected. Any new outdoor supply should be installed by a qualified electrician, and is notifiable under Part P in England and Wales. Keep plugs and extension leads away from the water. Our electrics guide has the detail.
5. Water care
Follow the manufacturer's routine. It usually means cleaning the filter regularly, using a suitable sanitiser and changing the water from time to time. Keep the lid on when you're not using the tub. It keeps the water clean, cuts running costs and keeps children and animals out. Rinsing off before you get in keeps the water fresher for longer.
6. Pairing with a sauna
Many people alternate hot and cold: a sauna session, then a plunge, repeated. If you're buying both, place them close together on firm bases with a safe, non-slip path between. Check that your power supply can handle the sauna heater and the chiller at the same time; your electrician can confirm this. Our sauna and plunge pairs are listed together, so you can see what goes with what.
Using a cold plunge safely
- Cold water can cause cold water shock: a gasp reflex and fast breathing in the first minute. Get in slowly, keep early sessions short, and don't plunge alone when you're new to it.
- Get out if you feel numb, confused or unwell.
- If you're pregnant, or have a heart condition, high blood pressure, Raynaud's or any other medical condition, ask your GP first.
- Always supervise children, and secure the lid when the tub isn't in use.
General guidance, not medical advice.
FAQs
How cold should a cold plunge be?
It's personal, and there's no single right answer. Many people start at a milder temperature and shorter sessions, then adjust. A chiller lets you set a temperature and keep it there. Each product page gives the lowest temperature the manufacturer states for that model.
Can I leave a cold plunge outside all year?
Most insulated tubs with chillers are designed for outdoor use. Check the product page for the operating temperature range. Protect the chiller and pipework from frost as the manufacturer instructs.
Do I need an electrician?
Not usually, if you have a suitable weatherproof, RCD-protected socket nearby and the chiller runs from a 13A plug. If you need a new outdoor socket or circuit, use a qualified electrician.
How much does a cold plunge cost to run?
Typically about £25–£50 a month for a chiller, depending on the model, the weather and your target temperature. The running-cost guide shows the maths.
Sources
- UK Government, Approved Document P (electrical safety): https://www.gov.uk/government/publications/electrical-safety-approved-document-p
- Ofgem, price cap from 1 October to 31 December 2026: https://www.ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026