Do you need a chiller at all?
If the plunge is part of what guests pay for, yes. Ice works for a private setup or an occasional event, but it does not scale commercially: you are buying, storing and adding ice every day, the temperature swings wildly between top-ups, and you have no way to hold a consistent 4–8°C across a full day of bookings.
A chiller turns the plunge from a daily chore into a managed system — set a target temperature and the equipment holds it. The question is not whether to chill, but how much chilling capacity the pool actually needs.
What size chiller does a cold plunge need?
Sizing depends on three things: water volume, bather load, and ambient conditions. A 500-litre plunge in a shaded indoor space with a handful of users a day needs far less capacity than a 1,000-litre outdoor pool running back-to-back sessions through a warm Saturday.
Every person who enters adds heat, and every degree of ambient warmth adds more. The practical mistake is sizing for the water volume alone — the chiller must not just cool the pool down once, it must recover temperature continuously while people are using it. An undersized chiller is the single most common cause of the warm-drift problem: the unit runs flat out all day and the water still climbs.
- Small private tubs (under ~500 litres, light use): compact chillers in the 1/4–1/2 HP class are typically adequate.
- Commercial plunge pools with regular daily sessions: expect to need 1 HP or more, sized against peak bather load, not just litres.
- Outdoor or sun-exposed pools in summer: allow meaningful headroom — solar gain on dark surrounds adds load all day.
- When in doubt, size up: an oversized chiller reaches temperature faster and cycles less; an undersized one runs constantly and still fails.
Do cold plunge chillers run 24/7?
In a commercial setting, effectively yes — and that is the right way to run them. Water holds temperature well, so a chiller holding 5°C overnight is only topping up losses, which is cheap. The expensive pattern is letting the pool warm up and pulling it back down from scratch each morning, which takes hours of full-power running and risks the pool not being ready for the first booking.
Continuous running also keeps water circulating through the filtration loop, which matters as much for water quality as for temperature. The realistic concern is not whether the chiller runs overnight, but whether it is recovering fully overnight — a pool that is still at 9°C at 6am after a busy evening is telling you the chiller is undersized or struggling.
Noise, placement and ventilation
Chillers are refrigeration units: they have a compressor and a fan, and they make noise comparable to a domestic heat pump or air-conditioning unit. Indoors, that hum can carry through a quiet wellness space; outdoors, it is rarely an issue but weather protection becomes one.
Two placement rules prevent most problems. First, the unit needs clear airflow around its condenser — a chiller boxed into a tight cabinet recirculates its own hot exhaust and loses capacity exactly when it works hardest. Second, keep pipe runs short and insulated: every metre of warm air around an uninsulated pipe is heat you pay to remove twice.
What does a chiller cost to run?
Running cost scales with the temperature gap between the water and its surroundings, the bather load, and how well the system is maintained. A well-insulated, covered plunge holding 5°C in a cool indoor space costs modestly to hold; the same pool uncovered in a warm room works far harder.
The biggest lever is a cover. Evaporation and surface heat gain are the largest continuous loads on the system, and an insulated cover during closed hours cuts both. The second lever is the filter: a clogged filter restricts flow, the chiller's heat exchange drops, and electricity consumption climbs while cooling falls. Operators often discover this through a rising electricity bill weeks after the water quality started declining.
The maintenance that actually matters
Chillers fail slowly before they fail completely, and the early signs are all visible in the temperature and recovery behaviour long before the unit stops.
- Filters: clean or replace on a schedule, not when flow visibly drops — restricted flow quietly cripples cooling capacity first.
- Condenser fins: dust and debris on the outdoor coil reduce heat rejection; a seasonal clean is cheap insurance.
- Recovery time: if the pool takes noticeably longer to return to 5°C than it did last month, something has changed — filter, refrigerant, or fouling.
- Water chemistry: unbalanced water corrodes heat exchangers; the chiller is usually the most expensive casualty of poor chemistry.
How do you know the chiller is doing its job?
The chiller's own display reads water at the intake — the coldest point in the system. It can show 5°C while the bathing zone sits at 8°C, and it cannot tell you how long recovery took after the lunchtime rush or whether the pool ever reached target overnight.
Operators get the honest answer from a separate temperature log in the pool itself: minute-by-minute readings that show the target band, the drift under load, and the recovery curve. That record turns 'the chiller seems fine' into a number you can check from your phone — and proof when a guest questions what they were served.