Today · post, October 19

SemiAnalysis sees 50GW added; leases back only part of it

SemiAnalysis forecasts about 50GW of data-center capacity added worldwide in 2027; this year's roughly US$1 trillion of signed leases covers about 20 to 33GW (our calculation), one basis among several

Concept illustration: a large pale-grey table lettered SEMIANALYSIS near its front edge, next to a small orange-and-blue octagonal emblem with circuit-like lines. In front, on a pale pink patch, three white box-shaped buildings with round fans on their roofs and small doors each sit on a stack of three thick brick-red binders held by dark straps with metal buckles, while five more such buildings stand directly on the table further back.

Why it matters: By our calculation, signed leases cover about 20 to 33GW of SemiAnalysis's 50GW, one basis among several, spread over 2027 and 2028. For the 50GW to hold, the rest has to come from hyperscaler self-builds and construction outside the US. The free post gives no detail on either.

SemiAnalysis forecasts about 50GW of data-center capacity added worldwide in 2027, based in part on this year's roughly US$1 trillion of non-cancellable leases at US$30 billion to US$50 billion of total contract value per GW (SemiAnalysis, 2026-10-19). Altimeter's Brad Gerstner says the amount actually built will be closer to 25GW (All-In transcript, 2026-09-17). SecondSource's arithmetic: those leases cover only about 20 to 33GW, spread across 2027 and 2028.

Not proven yet: the self-build construction detail is in the paid section, which hasn't been reviewed How we checked →

Judgment update: Our read: signed leases buy only about 20 to 33GW across two years, and less for 2027 alone, so they are one basis for the 50GW and cannot rebut it; the other bases' detail is in the paid section, which we did not read. For 50GW to hold, the rest has to come from the post's two other bases. One is self-build starts by the big US cloud providers. The post says two of these providers drive most of those starts. It names them only in the paid section. The other is construction outside the US, which the post says will clearly accelerate in 2027. Gerstner's 25GW is a single spoken line with no method given. It is his estimate of what actually gets built, and the show's context points to 2027. Neither he nor SemiAnalysis says whether the two figures cover the same scope. So it is unclear whether the 25GW can be set directly against the 50GW. The lease math could also understate. If the actual contract value per GW is below US$30 billion, the same US$1 trillion buys more GW. Leases would then carry a larger share. The next thing to watch is the 2027 capex guidance and self-build disclosures on the four big cloud providers' third-quarter earnings calls at the end of October. If the 2027 completed capacity they disclose, added to the 24GW or more of late-stage construction SemiAnalysis lists (most delivering in 2027, per the post), is still well below 50GW, that is a direct rebuttal. A slower rise in capex guidance is not enough on its own. If none of the four discloses comparable capacity figures, this call settles as "cannot be determined" and we will not substitute capex numbers.

Correction and addendum, October 21, 2026. This issue set the 20 to 33GW lease conversion against SemiAnalysis's 50GW and wrote that leases "can't carry" it, then judged whether 50GW stands by the growth in capex guidance. Leases are one of SemiAnalysis's bases; self-builds and construction outside the US are the others, with detail in the paid section we did not read, so the comparison cannot rebut 50GW. A growth rate in spending also does not translate into a level of capacity. The judgment update and the rebuttal condition above are rewritten accordingly.

Source and checks

This item ran in the brief of Oct 20, 2026, alongside 11 other items. How we checked it, the quote checks and what was still missing that day are on that issue's How we checked page.

Cite this item

SecondSource (2026). "SemiAnalysis sees 50GW added; leases back only part of it." https://secondsource.io/en/news/2026-10-20-1/. Accessed access date.