Capex is a promise; the cooling bill is part of the fine print. The AI build-out is usually discussed in terms of chips, but a rack full of high-power accelerators produces heat that conventional air conditioning cannot economically remove. That is why the industry is moving to liquid cooling — and why cooling is a growing line inside the data-center spend hyperscalers report.
The published application US20250159845A1, "Combined refrigeration system for high-density data center based on air-cooled air conditioner and liquid cooling" (published 2025-05-15), is a concrete window into that shift. The very framing — combining air and liquid cooling for high density — is an admission that air alone no longer suffices at AI rack densities. The IP exists because the thermal problem is real and expensive.
Build every estimate from the filing, and the filing gives you the aggregate. Hyperscaler annual reports describe investment in "servers, network equipment, and data centers" (Alphabet Form 10-K, FY2025, filed 2026-02-05) and in "cloud computing and AI infrastructure and datacenters" (Microsoft Form 10-K, FY2024). Cooling is inside "data centers" — not broken out, but unavoidably part of the number. As rack density rises, the cooling share of each new facility rises with it.
The payback math has an uncomfortable term here. Cooling capex earns no revenue directly; it is pure cost of keeping the revenue-generating accelerators alive. Every watt spent cooling is a watt not spent computing, which is why power-usage effectiveness is an operational obsession. Liquid cooling improves that ratio at high density — that is its business case — but it is upfront capex against a future operating saving, the classic infrastructure trade.
Distinguish disclosed from inferred. Disclosed: large, growing data-center investment. Documented in the patent record: active engineering on high-density combined cooling, implying air-only designs are being superseded. Inferred, not provable from either: what fraction of AI data-center capex is now cooling. Anyone quoting a precise cooling percentage is estimating; the filings do not itemize it.
For a capex-watcher, the lesson is to read "data centers" as a bundle that is shifting internally toward thermal infrastructure. The cooling patents are the leading indicator: when the IP moves to combined liquid systems for high density, the capex mix is moving the same way, even though no 10-K will ever spell out the line.