How Much Ice Do You Need for a Cold Plunge?

For every 10°F you want to drop the temperature of 100 gallons of water, you need roughly 20-25 lbs of ice. That's the baseline. So if your tap water comes out at 65°F and you want to plunge at 45°F (a 20-degree drop), you need 40-50 lbs of ice for a 100-gallon tub.

These numbers assume regular store-bought ice bags (typically 10 lbs each). Larger ice blocks melt slower and are slightly more efficient, so you might need 10-15% less with block ice compared to cubed ice.

The Cold Pod holds about 85 gallons. Figure 35-50 lbs of ice depending on season. At $3-5 per 20-lb bag, that's roughly $6-12 per fill.

The Ice Barrel holds 105 gallons but the upright barrel design means less surface area exposed to warm air, so ice lasts longer. 30-40 lbs typically gets you to the 40-45°F range.

Larger horizontal tubs (120-150 gallons) like the Arctic Warriors need 50-75 lbs of ice without the chiller running. This is one reason chiller-equipped tubs make sense at larger sizes — the ice math gets expensive fast.

In winter in a northern state, your tap water might come out at 45-50°F. You may not need any ice at all. That's free cold plunging.

In Phoenix in July, tap water can hit 85-90°F. You're looking at 70-100 lbs of ice to reach 45°F, plus the ice melts faster in the ambient heat. This is where a chiller goes from luxury to necessity — the ice cost in hot climates can hit $25-40 per session.

Shoulder seasons (spring/fall) are the sweet spot for ice-based plunging. Tap water around 55-65°F means manageable ice quantities and reasonable costs.

Reusable ice molds are the biggest money saver. A 4-pack of large ice block molds costs about $30 and produces roughly 38 lbs of ice per freeze cycle. If you have a chest freezer, you can produce all the ice you need for free (just electricity).

Other tricks: keep your tub covered when not in use to retain cold, plunge in the morning when water is coldest, drain and refill with cold tap water between sessions rather than trying to re-cool warm water, and add a reflective tub cover or emergency blanket over the lid to reflect heat.

Some users report adding salt to lower the freezing point, but this corrodes metal components and is hard on your skin. We don't recommend it.

If you're spending more than $40/month on ice, a chiller pays for itself within 2-3 years. If you live in a hot climate and plunge year-round, the breakeven is even faster. The Therafrost Pro at $1,899 is the cheapest chiller option — at $40/month in ice savings, it pays for itself in under 4 years. The convenience factor accelerates the decision for most people.

The real cost of ice isn't just money — it's friction. Driving to get ice, hauling bags, waiting for it to melt enough to reach target temp. That friction is why 60% of people who buy non-chiller cold plunges use them less than once a week after the first month. A chiller removes that friction entirely.