A question we get asked often is whether you should keep your chiller running or power off between cold plunge sessions? The answer is almost always "keep it on" and here's why.
Water Flow and Filtration
One of the most overlooked aspects of cold plunging is water flow. The benefit of owning a chiller is the constant circulation and filtration of water. This circulation, combined with proper sanitation methods (UV, Ozone, Hydrogen Peroxide) prevents bacteria, algae and biofilm from forming.
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When chiller is turned on: Water is consistently filtered and kept in motion, making it easier to maintain cleaner, sanitary water with fewer water changes.
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When chiller is turned off: Water becomes stagnant and is a breeding ground for bacteria. This increases the need for frequent water changes, stronger chemical treatments, and a higher risk of cloudy or foul-smelling water.
When owning a chiller, if water cleanliness and convenience are priorities, keeping your chiller running is the best option.
Energy Usage and Plunge Frequency
The other side of the debate is energy cost, think roughly $.50 to $1/day. Running a chiller around the clock isn’t free, and how often you plunge can make a small difference.
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Frequent plungers (daily or every other day): Keeping the chiller running nonstop makes sense. The water is always ready at your target temperature, and you avoid long cool-down periods.
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Occasional plungers (once per week): For those who cold plunge once per week, the logistical overhead of maintaining a chiller may outweigh the convenience. Only utilizing a chiller once a week involves several operational considerations that can impact both water hygiene and time efficiency. We strongly advise against leaving water in an inactive unit for an extended period of time. If the chiller is powered down for a week, the lack of circulation and filtration will lead to biofilms and organic impurities. At once a week, buying ice maybe more practical. However, if you prefer a chiller, we still recommend keeping the unit turned on.
Understanding Compressor Cycles
One of the most efficient aspects of modern chillers is the cycling of the compressor. When the chiller is on, although the pump runs 24/7, the compressor should not be setup to do the same. Instead, once the water hits your desired temperature (say 50°F), the compressor unit powers down (even with your chiller on) and only kicks back on when the water drifts a few degrees above your set range (say 55°F).
This means:
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The chiller isn’t constantly drawing full power.
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Energy use is more balanced, and your unit is protected from unnecessary wear.
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You can fine-tune the temperature swing (± degrees) to optimize efficiency. For example, allowing a 5–10°F buffer reduces how often the compressor cycles, extending compressor life and reducing utility costs.
In many cases, this balance, keeping your chiller running with a smart temperature buffer, is the best solution overall. Check with your manufacturer on how to adjust this setting as the longevity of your chiller can be dramatically influenced by this setting.
The Bottom Line
It almost always make sense just to keep the chiller turned on:
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Plunge daily or several times a week: Keep it running. Your water stays cleaner, colder, and always plunge ready.
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Plunge once per week: Keep it running unless you are willing to "fill, chill and drain" with every cold plunge session. We do not recommend letting water sit stagnant for long periods of time developing impurities and clogging up your chiller components.
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Best long-term practice: Allow your chiller to cycle the compressor with a reasonable temperature buffer. This ensures clean water, lower maintenance, reduced compressor wear and a manageable energy bill.
In short, convenience and water quality favor keeping it running, while rare users may choose to shut it down between plunges.
