What an ice bath chiller does, and how it differs from ice
A chiller works on the same closed-loop refrigeration cycle as a fridge or a heat pump: a compressor, a condenser, an expansion valve and a heat exchanger, with a pump pushing your tub water through the exchanger and a thermostat cycling the compressor to hold the temperature you set, usually to within about 1 to 2°C of target. In plain terms, it is the "set a temperature, skip the ice" alternative to filling a tub with cold water and bags of ice.
The difference from ice is convenience and consistency. Instead of buying and hauling ice for every session, you dial in a temperature and the chiller holds it. Paired with integrated filtration, that keeps the same water usable for weeks rather than draining and refilling constantly.
There are two ways to buy. A standalone chiller connects by hose to a compatible tub, so you match it to a cold plunge tub you already own or buy separately. An all-in-one chiller tub has the chiller built in, which removes any compatibility guesswork at a higher price. If you are not ready for either, a portable ice bath filled with cold water and ice is the cheaper way to start, and you can add a chiller later.
The specs that matter
Cooling capacity: how cold it holds, and how fast. Small plug-in chillers are rated by compressor size, from about 1/4 HP up to 1 HP; larger heat-pump units quote a cooling output in kW instead. Bigger cooling power pulls a tub down faster and holds it better against heat creeping back in. Note that HP and cooling kW describe cooling power, which is not the same as the unit's electrical draw (see running cost, below). Practical low temperatures for UK home units sit around 2 to 5°C, and the coldest claims are best-case, well-insulated figures rather than guarantees.
As orientation, the table below maps compressor size to tub volume. These figures come from US sizing guides converted to metric, so sense-check them against each unit's own UK spec, and remember that ambient temperature matters: a chiller loses roughly 15 to 25% of its cooling as the air warms, so it works harder and holds less cold in a hot summer or a warm room.
| Compressor | Suits water volume | Rough cool-down (about a 17°C drop) |
|---|---|---|
| 1/4 HP | about 190 to 285 L | 3 to 4 hours |
| 1/2 HP | about 285 to 450 L | 2 to 3 hours |
| 3/4 HP | about 450 to 660 L | 1.5 to 2 hours |
| 1 HP | about 660 to 950 L | 1 to 1.5 hours |
Does it also heat? This is the biggest feature split. Heat-capable units double for a warm soak and, more usefully, for the hot side of contrast therapy, so one tub can run both halves of the hot-then-cold ritual. Cooling-only units are cheaper but cold only. If you want contrast therapy from a single tub, prioritise a model that heats.
Filtration and sanitisation. Ozone (O3), UV and micron filters keep the water clean so you are not draining and refilling every few days. A filter-and-chiller combination is a common want, and better units pair ozone with a particle filter and a hair filter.
Flow rate and pump. The circulation pump moves water through the heat exchanger. Some standalone chillers include the pump; others are sold without one, so you buy it separately. Published flow-rate figures are patchy in this category, so check the spec and treat a missing figure as a question to ask the seller.
Power draw (kW) and efficiency. Electrical draw is separate from cooling power. A compact standalone chiller might draw around 0.45 kW when running. Inverter heat-pump units draw more at full tilt but are far more efficient and cycle less, so a bigger, better unit is not automatically dearer to run. Draw and duty cycle drive the running cost.
Noise and siting. Compressors make noise and are best sited outdoors, in a garage, or well away from a bedroom wall. Look for a dB figure and check the distance it is measured at; some units publish one, some do not.
Tub compatibility. Standalone chillers connect by hose, often with cam-lock fittings, to a tub with an inlet and outlet, or with hoses dropped into an open tub. All-in-one tubs remove the compatibility question entirely.
What a chiller costs to buy
As a guide, standalone home chillers broadly span roughly £700 to £1,600 depending on capacity, whether they heat, and filtration. Cooling-only compact units sit at the lower end; heat-and-cool heat-pump units sit higher. All-in-one chiller tubs start nearer £4,000 and rise from there, because you are also paying for the tub, integrated heating and built-in filtration. At the very bottom of the ladder, a portable tub with no chiller can be had from the low hundreds, so the choice is really about how much hassle you want to remove.
What a chiller costs to run
Running cost comes down to three things: the chiller's electrical draw in kilowatts (kW), how many hours it actually runs, and your electricity unit rate in pence per kWh. The sum is simple: kWh used = power draw (kW) x hours run, and cost = kWh x unit rate.
Take a compact standalone chiller that draws about 0.45 kW when the compressor is working, at 26.32p per kWh, the Ofgem price cap average for 1 October to 31 December 2026:
On demand (cool the tub before a session, then switch off): roughly 1.5 hours to bring the water down is about 0.45 kW x 1.5 h = 0.68 kWh, or around 18p a session. Used daily, that is roughly £1.25 a week.
Always on (holding temperature around the clock in a well-insulated, covered tub): a thermostatic chiller does not run flat out, so assume it runs about a third of the time. That is about 0.45 kW x 24 h x 0.33 = roughly 3.6 kWh a day, or about 94p a day, roughly £6 a week and £25 to £30 a month.
These are estimates to show the method, not a promise. Real cost swings with insulation and a good cover, the ambient temperature, your target temperature, and whether you run on demand or always on. Plug your own unit's kW and hours into the formula to get a figure you can trust.
Guide prices, correct as of July 2026, with running costs based on 26.32p per kWh (Ofgem cap, 1 October to 31 December 2026). The energy price cap changes quarterly, so check current rates before budgeting. Guide prices are typical UK costs, not live prices.
Building a DIY chiller: honest, with a safety warning
The cheaper DIY routes are a general aquarium or water chiller plumbed to a stock tank, an IBC tote or a home-made tub, and a chest-freezer conversion. They can cost noticeably less, which is why they are popular. Be clear-eyed about the trade-offs: aquarium chillers are not designed for continuous cold-plunge duty and can struggle to hold the lowest temperatures, support and warranty are weaker, and both routes raise real water-and-electricity safety issues that a purpose-built, IP-rated unit is engineered around.
A chest-freezer conversion is the cheapest and the riskiest, because you are putting water in an appliance never intended to hold it. If you go the DIY route at all, treat the electrics as a job for a qualified electrician, insist on RCD protection, and never improvise with an indoor extension lead outdoors.
The electrics and safety you must get right
A chiller is mains electrical equipment running next to a tub of water, often outdoors, so the supply matters as much as the unit. Part P of the Building Regulations covers electrical work in dwellings and in gardens supplied from the dwelling, and installing a new circuit is notifiable work. That means it must be carried out by an electrician registered with a self-certification scheme, or signed off by a registered third party, or notified to local-authority building control. Use a qualified electrician for any fixed outdoor supply.
The supply should be RCD protected and use weatherproof, correctly rated sockets and connectors. Buy IP-rated units. The base needs to be level and drained, and it needs to take the weight: an all-in-one tub can be well over 500 kg once filled, so the ground under it has to cope. If you would rather have the tub and its electrical supply designed and fitted for you, that is exactly the kind of enquiry the installation service is built to route to a vetted local installer.