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Data center cooling, explained simply

Cooling carries the heat out. You pay once to build it, then every month in power, and sometimes in water.

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The cheap build and the cheap month are often different machines. Ranges are directional. Ask a vendor before a number goes into a model.

Ten-second cheat sheet

Upfront is the build. The monthly bill is mostly electricity. Dense AI means racks from about 40 kW up, including a GB200-class rack near 120 kW.
Setup Upfront Bill each month Water Fits dense AI?
Air Lowest Highest power Medium to high if the tower is wet No
Liquid, closed loop, dry coolers Medium to high Lower power Very low Yes
Liquid plus evaporative Medium Lower power High Yes
Immersion, dry rejection Highest Often the lowest power Very low Yes

Three builds

Air

Room air through the servers. A wet tower outside can spend water.

Upfront
$2 to $4 million per MW
Each month
Highest power
Water
High if the tower is wet

Direct-to-chip liquid

A plate on the chip, a CDU between loops, then a cooler outside. The CDU box alone is often cited at $0.10 to $0.20 per watt.

Upfront
$3 to $6 million per MW
Each month
Lower power
Water
Almost none if dry

Immersion

Tanks, fluid, and servers built for the bath.

Upfront
Highest
Each month
Often lowest power
Water
Almost none if dry

Upfront

Longer bar, more money before the hall turns on. The bars are a shape, not a price list.

Each month

PUE is building power divided by power that reaches the computers. Air spends the most electricity. A wet tower spends the most water.

When air stops

Under about 15 to 20 kW per rack, air is enough. From 30 to 40 kW it is a stretch. A GB200-class rack near 120 kW ships with cold plates.

Where the heat goes

Dry coolers. More metal, more fan power on a hot afternoon, almost no water, less salt on the metal.

Wet towers. Less electricity on hot days. A water bill, and corrosion if the coast is salty.

Brazil’s Redata benefit asks for 0.05 L/kWh or less, measured yearly. A dry cooler can meet that. A wet tower spends the water the statute counts. On a hot coast, that is the choice.

How the studies drew the box

Each study measures a different box. Read them as separate scopes.

  • Schneider WP282, a whole 2 MW building in 2019. At 10 kW per rack, air and immersion were about $7.02 and $6.98 per watt. At 40 kW, immersion was about $6.02, mostly because the building got smaller.
  • Data Center Scope reads Turner & Townsend 2025 to 2026 as a 7 to 10 percent construction premium for a liquid hall, and cites Uptime for a 5 to 10 percent direct-liquid add.
  • Adam Silva, 16 racks, 2026: advanced air about $1,800 to $3,200 per kW, direct-to-chip $3,500 to $5,000, single-phase immersion $4,300 to $6,500.
  • A secondary summary of IDTechEx, December 2025, put one GB200-class rack’s cooling hardware near $55,000, of which the CDU was near $23,000. Pipe and yard gear sit on top. AI Tool Discovery.
  • TechTarget on Schneider WP220: liquid supply from 32°C to 45°C cut water about 66 percent in a Dallas case and about 82 percent in Paris. PUE moved under 1 percent.
  • Uptime, April 2026: a dry cooler can match evaporative PUE in many climates. Evaporative PUE is bought with water.
  • NVIDIA puts a DGX GB200 rack near 120 kW, with manifolds and cold plates. Schneider’s liquid infrastructure is cited up to 132 kW per rack.

Field notes, not cost sources. @omijagun on 5 October 2026 put GB200 racks up to about 140 kW against halls built for 10 to 15 kW. @AliLenjani a day earlier pointed at galvanic corrosion in the CDU and the cold plates.

Names on the package

Cold plates and CDUs
CoolIT , Motivair , nVent , Boyd , Asetek , Vertiv , and Schneider
Outdoor coolers
Munters , STULZ , Vertiv , and Schneider
Immersion tanks
GRC , Submer , and LiquidStack

Full list on the glossary player list.

Have a site where this choice is live?

We originate renewable power for halls in the 100 MW to 3 GW range. Cooling decides whether the site can take the workload.

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Questions

What does data center cooling do?

It carries heat out of the building. Almost every watt the chips use becomes a watt of heat. Cooling is the fans, cold plates, tanks, pumps, and outdoor boxes that move that heat outside.

How much does data center cooling cost to build?

As a planning range, air cooling is often about $2 to $4 million per megawatt of IT. Direct-to-chip liquid is often about $3 to $6 million per megawatt, or about 1.5 to 2 times the air cooling kit. Immersion usually costs more to install than cold plates. These are directional ranges, not a bid.

When is air cooling enough for a data center?

Below about 15 to 20 kW per rack, air is usually enough and it is the cheapest install. Above about 30 to 40 kW per rack, air cannot carry the heat. Current AI racks, including NVIDIA GB200-class racks around 120 kW, are built for liquid cooling.

Does liquid cooling use water?

The loop on the chip can be closed, so it does not consume water. Water use depends on how you reject the heat outside. Dry coolers use almost none. Evaporative towers and adiabatic assist use water on purpose, to cut electricity on hot days.

What is a CDU?

A coolant distribution unit. It sits between the cold plates and the building loop, moves heat off the rack, and keeps the IT fluid separate from the outdoor loop. The box alone is often cited around $0.10 to $0.20 per watt, before pipe, coolers, and install.

What is the difference between cold plates and immersion?

A cold plate bolts liquid onto the hottest chips. Immersion puts the whole server in a tank of fluid that does not conduct electricity. Cold plates are the common path for current AI racks. Immersion usually costs more to install and often uses less electricity to run.

What cooling choice matters for a dense AI hall?

Liquid is already required, so air versus liquid is the wrong comparison. Compare closed-loop dry coolers with evaporative heat rejection, and compare cold plates with immersion. Dry costs more in fans or metal and uses very little water. Evaporative saves electricity on hot days and spends water.

Sources

Checked 6 October 2026. Machine-readable copy at /cooling.md.