Air, hydro, or immersion cooling: choosing by your facility, not the hype

Scroll the catalog and the pattern is obvious: the hydro and immersion units post the biggest hashrate numbers. An S21 XP Immersion at 300 TH/s makes the air-cooled S21 at 200 TH/s look like the lesser machine. So immersion must be the upgrade, right?

Only if your facility is built for it. Cooling is the one ASIC decision where the highest-spec option is frequently the wrong buy, and choosing it for the headline number is how operators end up with expensive hardware they cannot properly run.

Air cooling: the default for a reason

Air-cooled units are self-contained. Power in, ethernet in, exhaust out. They need a room you can ventilate and keep within the unit's ambient temperature spec, and that is essentially it. No plumbing, no coolant, no dielectric fluid, no tank.

Choose air if: you are deploying anything from a single unit to a mid-sized fleet, you do not already have liquid-cooling infrastructure, and you want the simplest possible operation. For the large majority of buyers, including most of our scaling customers, air cooling is the correct answer. The S21, S21+, and S21 Pro live here.

Hydro cooling: more hashrate, but you bring the loop

Hydro units circulate liquid coolant through the miner and reject heat through an external loop, typically a dry cooler or a heat exchanger you provide. The payoff is real: removing the thermal ceiling lets the same silicon run much harder, which is why a hydro unit posts 400 to 500 TH/s where its air-cooled sibling posts 200.

Choose hydro if: you have, or are building, a facility with a coolant loop and heat-rejection infrastructure, you are deploying at enough scale to justify that infrastructure, and you want maximum hashrate density per rack slot. Hydro is a facility commitment, not a per-unit upgrade. The S21+ Hyd, S21 XP Hyd, and the Whatsminer M63 hydro series live here.

Immersion cooling: maximum density, maximum commitment

Immersion submerges the hardware in a dielectric fluid that carries heat away directly. It delivers the best thermal performance and the quietest, densest deployments, and it requires the most purpose-built facility: tanks, fluid, pumps, heat exchangers, and a build designed around the method from the start.

Choose immersion if: you are building a dedicated, large-scale facility around the method, you have the capital and the engineering to do it properly, and the density and longevity benefits justify the build. This is not a retrofit you bolt onto a spare room. The S21 XP Immersion and S23 Immersion live here.

The mistake to avoid

The classic error is buying a hydro or immersion unit for the hashrate number, then discovering the facility cannot support it. A hydro miner without a coolant loop is not a fast miner; it is an inert box. The cooling method has to match the building before the hashrate number means anything.

The reverse mistake is rarer but real: running air-cooled units in a space you cannot ventilate, then watching them throttle in summer because ambient temperature climbed past spec. Air cooling is simple, but it still needs a room that can stay within the unit's temperature range under load.

How to decide in one question

Ask: what does my facility already support? If the answer is "a ventilated room", buy air-cooled and do not overthink it. If the answer is "an existing coolant loop with heat rejection", hydro is on the table. If the answer is "a purpose-built immersion facility", you already know what you are doing. Let the building choose the cooling, not the spec sheet.

Not sure which your facility supports?

Describe your space, the power available, and the ambient conditions, and we will tell you honestly which cooling method fits and which units match it. We would rather sell you the air-cooled unit you can run than the immersion unit you cannot.

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