Published October 20, 2026 · Evidence reviewed October 21, 2026

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maincubes mainHub Berlin / Nauen (BER02)

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Power works reach a visible milestone

maincubes’ mainHub Berlin campus in Nauen has reached the topping-out stage for its substation structure. Contractor JSM reported the October 13 event on October 19. The milestone concerns the power infrastructure: it does not establish energized grid supply, completed data halls or operating AI capacity.

One campus, three different capacity measures

The operator reports a signed 200 MW grid-connection agreement with E.DIS. Its current technical factsheet gives a design-dependent campus range of 144–186 MW of IT capacity, while JSM calls the substation a 200 MVA installation. These are different measures and are neither additive nor interchangeable. BER02 is the first of up to six planned buildings; the campus is in Nauen, Brandenburg, rather than Berlin municipal territory.

Approvals and delivery

Nauen’s July 2, 2025 official notice establishes that the Rechenzentrum zoning plan took effect. That is not the individual building permit for the data halls. Local reporting says a hall/campus permit exists, but the underlying primary permit was not obtained for this review. The operator’s live English and German project pages list Q3 2028 for BER02, while its undated English factsheet still lists Q1 2028. The conflicting targets do not establish a confirmed service date; the reviewed documents do not establish a revision chronology or a confirmed delay.

Capital is disclosed at platform level

DTCP’s January 2026 announcement describes a €2.475 billion financing package for maincubes: €1.775 billion committed and a €700 million uncommitted accordion. Its uses extend across portfolio refinancing and development. The package is not Nauen’s budget, a verified site allocation or evidence of money spent at the campus. Project capex therefore remains unknown.

Investor takeaway — analysis

The tangible change is progress on the electrical infrastructure required before customers can use the campus. The evidence is stronger for construction of that infrastructure than for the timing or economics of future IT service. The next useful evidence is equipment installation and energization, phase-specific permits, tenant commitments and first customer acceptance—not a larger headline capacity number.

Identity and boundaries

This record excludes operational maincubes BER01 in Berlin, Vantage BER2 and neighboring Rechenzentrum 2 planning. No named tenant, GPU order, prelet percentage, measured operating PUE or binding heat-offtake contract was verified. Technical certifications and sustainability features in the operator factsheet are targets or plans, not verified operating achievements.

Sources and scope

1. City of Nauen — Amtsblatt No. 4: Bebauungsplan Rechenzentrum
2. maincubes — Zoning plan approved and grid connection agreement signed
3. maincubes — BER02 technical factsheet
4. JSM Group — Topping out at maincubes Berlin campus
5. Unser Havelland / Typemania — Strom für das Rechenzentrum: Richtfest für das Umspannwerk in Nauen
6. DTCP — maincubes secures €2.475 billion platform financing
7. maincubes — Company and investor information
8. DTCP — DTCP to become majority shareholder
9. maincubes — Live BER02 project page (English and German editions)