Immersion vs hydro vs air cooling: choosing how to cool bitcoin miners

No method wins everywhere. The machines settle most of it: a standard machine can be air-cooled or immersed, while a hydro model needs a coolant loop. After that, the site and the climate decide.

Pick hydro if

• You are buying new machines and a hydro model, such as the Antminer S21+ Hyd., fits your plans.
• You want dense racks at a site with three-phase power and room for a coolant loop and an outdoor cooler.
• You want no fans at the rack and no fluid around the electronics: the coolant stays inside the cold plates and pipes.

Pick air or immersion if

• You already own air-cooled machines: run them on air, or immerse them once their fans are removed.
• The site is mild and clean, with power and room to move large volumes of air, and you want the simplest, lowest up-front build: choose air.
• The site is dusty or noise-limited and you want to keep standard machines: immersion shields the boards from dust and runs much quieter than air.

Every bitcoin miner turns almost all the power it draws into heat. The three ASIC cooling methods differ in what carries that heat away from the chips:

• Air: fans built into the miner pull air across heat sinks on the hashboards and blow it out the back. The building's job is to supply cool air and get rid of hot air.
• Immersion: the whole miner sits in a tank of dielectric, meaning non-conductive, fluid. The fans are removed, heat passes from the chips into the fluid, and the fluid is pumped through a heat exchanger and back.
• Hydro: coolant flows through cold plates clamped over the chips inside a machine designed for it. The machine has no fans, and coolant leaves through ports on the case to a loop that carries the heat outside.

So air and immersion can cool the same standard machine, while hydro needs a hydro model from the factory. That one difference settles many decisions before efficiency comes up at all.

Air cooling is the simplest of the three. There is no fluid to buy or manage, no tank or manifold, and every standard miner is built for it. Even an immersion operator noted in 2023 that most operators relied on air-cooled setups.

It makes sense when you already own air-cooled machines, the site has power and room for large volumes of air, the climate is mild enough for most of the year, and you want the lowest up-front build. Its costs show up elsewhere: fan noise, dust carried through the machines, and hot days when the air coming in is too warm to cool them fully. The building also has to move a great deal of air, which shapes how densely machines can be packed.

Air-cooled machines are not what Proton hosts. If you run them at home, home mining vs hosted mining covers the circuit, noise and heat questions.

Immersion's strongest case is converting machines you already have. Because a standard air-cooled miner can be immersed once its fans are removed, a site can move an existing fleet to liquid cooling without buying hydro models.

Its other strengths, as an immersion operator describes them: the fluid shields machines from dust and debris, the setup is much quieter than air cooling, machines can be run harder through overclocking, and the warm fluid can be put to other uses such as heating greenhouses.

What it asks of the site: tanks, dielectric fluid, pumps and a heat exchanger; a plan for leaks, since a leak in a single-loop system can lose some or all of the coolant; and slower, messier maintenance, because every machine comes out of the tank dripping. Before removing the fans, check the manufacturer's warranty terms. Two-phase immersion, where the fluid boils off the chips, exists but is described by an immersion operator as still experimental, more expensive and needing more frequent maintenance than single-phase.

Hydro makes sense when you are buying new machines and want them densely racked at a site built around a loop. The machine is designed for liquid from the factory, so there is no conversion, no tank, and no fluid around the electronics: coolant stays inside the cold plates and pipes.

Take the Antminer S21+ Hyd. as an example. Bitmain's manual rates the 395 TH/s version at 5,925 W and 15 J/TH, with coolant entering the machine at 35 °C, and lists an operating range for incoming coolant of 20 to 50 °C. It connects through OD10 coolant ports, needs a flow of 8.0 to 10.0 litres a minute, and runs on a three-phase 380 to 415 V supply.

What it asks of the site: three-phase power, pumps and manifolds that deliver that flow to every machine, a heat exchanger, a cooler outside, and coolant kept within its specification. Hydro cooling bitcoin mining explains the two loops part by part, and hydro miner hosting covers what a hydro machine needs from a host.

There is no single answer, and be wary of anyone who gives one. Published comparisons of immersion and hydro cooling disagree, and an overhead percentage depends on who measured it, on which system and in which climate.

Two things are worth separating. The machine's own efficiency, in joules per terahash, is set by its chips, how it is tuned and the temperature it runs at. The site's overhead, meaning the power spent on fans, pumps and coolers on top of the miners, depends on the design and the climate as much as on the method.

If a host or vendor quotes an efficiency or overhead figure, ask where it was measured, over what period, and in what climate.

For the S21+ Hyd., Bitmain's own curve shows the effect of coolant temperature: efficiency holds at 15 J/TH in the lower part of the inlet range and slips to between 16.8 and 17.3 J/TH, depending on the coolant, with coolant entering at 50 °C.

Work through three questions in order. Most decisions are made by the first.

1. Which machines? If you already own air-cooled machines, the choice is air or immersion. If you are buying new, hydro models open the third option.
2. Which site? Dust, noise limits, floor space, three-phase power, and whether the site can take tanks or a coolant loop narrow the field quickly.
3. Which climate? Hot summers are where air cooling struggles, since the incoming air is what cools the machine; a liquid loop still needs a cooler sized for the hottest days. A mild, clean site may never need more than air.

Then cost the whole build, not just the cooling: tanks or manifolds, fluid, pumps, coolers, the labour to maintain them, and the machines themselves. If you would rather not build or run a loop at all, a host that runs one is the alternative; how to choose a bitcoin mining host covers what to ask.

Proton's planned containers are hydro-cooled on a closed water loop, with no air crossing your machines, and the coolant temperature range is confirmed per site, in writing. Hosting is for hydro-capable machines bought through Proton. Capacity, timing, rate and terms are confirmed per site and set out in writing before anything ships.

A good fit if

• You have chosen hydro and are buying machines such as the S21+ Hyd. from the Proton catalogue.
• You want the loop and the cooler run by the host, with coolant inlet and outlet temperatures monitored per machine.
• You want power metered at the PDU and your hashrate on your own pool.

Not a fit if

• Your machines are air-cooled, or you want them immersed: hosting is for hydro-capable models only.
• Your machines were bought elsewhere: hosting is only for machines bought through Proton.
• You need a hosting start date now: proposed locations have no confirmed start date.