Where things stand
Cooling is the second-largest capex line in a datacenter and the second-longest lead time. Turner & Townsend’s 2025 index puts mechanical including equipment at 22% of an air-cooled US build and 33% of a liquid-cooled one, with a 7 to 10% premium for liquid (Turner & Townsend); that is $2.2 million to $3.2 million per MW at the $9.8 per watt Phoenix and Columbus baseline. Water-cooled chillers over 1,000 tons are quoted at 50 to 70 weeks, air-cooled over 500 tons at 40 to 60, CDUs at 30 to 50 (Origin Partners, May 22 2026). Munters’ orders booked in December 2025 deliver into Q1 2028 (Munters). The buyer’s arithmetic is in Chillers Are the 60-Week Problem.
Adoption lags the headlines. Uptime’s 2025 survey still has 75% of operators on CRAH or CRAC with containment as the primary method (Uptime Institute, paywall), and the 2024 survey found direct liquid cooling at 22% of operators and typically 10% of racks or fewer where present (Network World). Liquid wins every new AI hall and almost none of the installed base. This roadmap covers both.
Air to direct-to-chip to 600 kW
| Technology | Practical ceiling per rack | Status in 2026 | Source |
|---|---|---|---|
| CRAH or CRAC with containment | about 20 to 30 kW | 75% of operators’ primary method | Uptime 2025 |
| Rear-door heat exchanger | 30 to 40 kW passive, over 50 kW with fans | retrofit bridge | SemiAnalysis |
| Single-phase direct-to-chip with CDU | 120 to 250 kW; 250 kW shown at 40 C inlet | “the vast majority of liquid-cooled capacity coming online” | Dell’Oro, January 2026; Introl |
| Two-phase direct-to-chip | marketed for 250 kW and above | small base; JCI led Accelsius’s $65M Series B, January 2026 | Accelsius |
| Single-phase immersion | 100 to 200 kW per tank | niche; hyperscalers chose cold plates for NVL72 | Dell’Oro |
| Two-phase immersion | high | fluid supply broke: 3M ended Novec at end-2025 | Schneider, May 2026 |
The load that forces the change: GB200 NVL72 at 132 kW thermal design power, 115 kW to liquid and 17 kW to air (Pantheon); Rubin Ultra NVL576 in the Kyber rack at about 600 kW in the second half of 2027 (DCD); GPU TDPs above 4,000 W by 2029 per Dell’Oro. Our forecast: single-phase cold plates carry every GPU generation through 2029; two-phase and immersion stay under 10% of liquid-cooled capacity in this horizon.
Inlet temperatures and the W-series
NVIDIA’s reference loop runs 45 C in and 65 C out (FinmoConf), which is an ASHRAE W45 facility-water class (CIBSE Journal, September 2025) and warm enough to skip chillers in most US climates with dry or adiabatic coolers; xAI’s Colossus 2 runs about 130 dry coolers and 135 adiabatic units (Measured AI, verify). Water-cooled chillers reach a COP near 7, air-cooled near 4, so a 2 MW air-cooled unit draws about 500 kW at 35 C ambient (SemiAnalysis). Fleet PUE tells the same story from two ends: Uptime’s survey average is 1.54, flat for six years (Uptime); Google’s fleet ran 1.09 in 2025 (Google).
What it strands. A chiller plant specified for a W27 loop in 2024 is oversized for a W45 hall in 2027. Write the W-class and the UQD fitting spec into the RFQ or you have single-sourced the loop; the standards list is in How to Write an RFQ for Capital Equipment.
CDU generations
In-rack CDUs (tens of kW) serve retrofits; in-row CDUs (a few hundred kW to about 1.3 MW) serve a row of NVL72; facility CDUs above 1 MW use liquid-to-liquid exchangers with redundant pumps (SemiAnalysis). Carrier planned a 2.5 to 2.6 MW CDU for Q3 2026 and a 5 MW unit by year-end (Carrier Q2 2026 slides via Investing.com). Taiwan makes the parts: AVC holds an estimated 40 to 50% of GB200 and GB300 cold plates (TVBS); Auras expects a few hundred CDUs in 2026 and 2,000 in 2027 (TVBS). No vendor publishes a CDU list price; trade estimates run $500 to $800 per kW installed (Energy Solutions, verify). The majors bought their way in at 22.5x (Eaton, Boyd Thermal, $9.5B) and 29x (Ecolab, CoolIT, $4.75B) forward EBITDA (Nasdaq; Ecolab). Our forecast: the CDU is bundled with switchgear and UPS in reference designs by 2028, and the standalone CDU quote disappears for hyperscale; colo and enterprise keep buying it as a line item.
Water
An evaporative tower loses about 1.8 gallons per ton-hour; at about 285 tons per MW that is roughly 6 million gallons of makeup a year per MW at four cycles (RPM Water, citing EPA WaterSense). Google’s datacenters consumed 10.9 billion gallons in 2025, up 34% (Axis Intelligence summarising Google’s 2026 report, verify); Microsoft’s fleet WUE fell to 0.27 L per kWh but its Phoenix sites exceed 2.0 (Microsoft, June 2026). Microsoft’s zero-water design pilots in Phoenix and Mount Pleasant come online in late 2027 (Microsoft). The trade is water for electricity: dry rejection needs warmer loops or more chiller hours, so WUE and PUE move against each other and the buyer picks one.
Refrigerants
| Date | Instrument | What it did | Source |
|---|---|---|---|
| January 1 2025 | AIM Act Technology Transitions rule compliance date | new comfort-cooling chillers and residential AC under 700 GWP; R-454B and R-32 become the volume products | 88 FR 73098 |
| March to September 2025 | R-454B cylinder shortage | lead times to 10 weeks, cylinders $700 to $2,000, demand 5 to 10x forecast | ACCA, June 2025 |
| October 3 2025 | EPA proposed reconsideration | compliance dates and limits reopened | 90 FR 47999 |
| May 26 2026 | Final reconsideration, effective July 27 2026 | install deadline removed for pre-2025 systems; IPR and semiconductor chiller dates to January 1 2030; comfort chiller limit unchanged | 91 FR 31284 |
| January 1 2029 | HFC allowance step | production and consumption cap falls from 60% to 30% of baseline | EPA |
For chillers the paths are R-1234ze (GWP 7, A2L) and R-513A (GWP 631, A1 drop-in). An A2L machine room means new ventilation, leak detection and technician certification that never appear in the equipment quote.
Chiller capacity: who has a 2027 slot
| OEM | Capacity evidence | Timing | Demand evidence | Read | Source |
|---|---|---|---|---|---|
| Trane | applied capacity 4x in three years, Grand Rapids | 2026 to 2027 | $6B of $12.1B backlog is for 2027 | best odds of a 2027 slot | Q2 2026 8-K |
| Carrier | Charlotte +50%; new plant doubles North American output | 2025 to 2026 | 2026 datacenter sales covered by backlog; orders +300% | 2026 sold, 2027 open | 8-K July 28 2026 |
| Johnson Controls (York) | no plant-level disclosure found | backlog $21.0B, +32% | demand slot dates in writing | 8-K July 29 2026 | |
| Munters | Virginia chiller plant live Q2 2026, ramping | 2026 ramp | orders deliver to Q1 2028 | chillers only, around the ramp | Munters |
| Modine (Airedale) | North American expansion online FY2027 | to March 2027 | $4B reserved by one buyer with a $165M deposit | 2027 largely pre-sold | Modine 10-K |
| Vertiv | no chiller plant disclosure found | $15.0B backlog ships in 12 to 18 months | slots follow the backlog | Vertiv 10-K |
Backlogs and book-to-bill for these six are tracked quarterly on the Book-to-Bill League Table; the deposit terms in The $60 Million Deposit. Our forecast: large water-cooled chiller lead times stay above 40 weeks through 2027 and fall toward 30 in 2028 as Trane, Carrier and Munters run at rate; CDU lead times fall first, in 2027, as Taiwanese volume arrives.
What would change this roadmap
- A hyperscaler standardising on W45 or warmer across a region. It removes the chiller from the new-build spec for that region and turns the 2028 chiller relief into a 2027 glut; the water bill falls and the electrical bill rises.
- A published Trane, Carrier or JCI lead time under 30 weeks for 1,000-ton water-cooled units before mid-2027. It would mean the capacity table above landed early and would move the 2028 date forward.
- EPA moving the comfort-cooling chiller GWP limit or the 2029 HFC step. The May 2026 reconsideration left both alone; a change would reopen the R-134a versus R-513A versus R-1234ze decision on every chiller RFQ in the horizon.