Technical Companion · Part VI

The Modular Datacenter Stack: engineering the site

Grid interconnection queues, MV substation design, factory-test protocols, structural floor loading for 3,000-pound racks, and the water and wastewater arithmetic that governs where a 500MW campus can actually be built.

Companion to the The Modular Datacenter Stack essay (Part VI of six). Use this piece for the interconnection, protection, structural and site-engineering arguments; use the main essay for the market map, vendor structure and TAM.

Section 1: Grid interconnection queues, not construction schedules, set the pace

The published construction schedule for a hyperscale AI campus, from ground-breaking to first-power, is 18–24 months. That schedule assumes the campus already has an approved grid interconnection agreement with the local transmission operator. If it does not, the effective timeline is 4–6 years, because the queue for large-load interconnection studies is that long in most US ISOs and most European transmission areas.

A grid interconnection request for a 500MW load triggers, at minimum, a feasibility study, a system impact study, and a facilities study. Each of these takes 6–12 months of transmission-planner time. The queue for those studies is now filled with wind, solar, battery storage, industrial electrification, and increasingly, datacenter load. In PJM (the largest US ISO by capacity), the interconnection queue has grown from ~200GW in 2020 to over 1,100GW in 2025. Approval timelines have stretched from 18 months in 2015 to 4–5 years in 2025. MISO, ERCOT, ISO-NE, CAISO all show similar patterns. Europe (ENTSO-E territory) has parallel queues at national TSOs; Ireland's EirGrid moratorium on new Dublin datacenter interconnection (2022 onward) is the sharpest visible example of the constraint.

US ISO interconnection queue growth
Active interconnection queue (GW of requested generation + load), major US ISOs, 2020–2025
FERC Form 715 and Lawrence Berkeley National Laboratory interconnection queue reports (2021–2025). PJM data from PJM Queue Points reports. Approval timelines from LBNL "Queued Up" annual reports.
The datacenter siting decision that everyone underestimates. The choice of where to build a hyperscale campus is not primarily about land, tax incentives, or labour cost. It is primarily about which utility service territory has grid capacity that can be interconnected within the schedule the operator can tolerate. Sites in slow-queue territories (PJM, CAISO, Ireland) are being deferred or downsized. Sites in fast-queue territories (ERCOT, SPP, parts of the US Southeast, Malaysia, some Middle East locations) are being oversized. The "modular" advantage in this context is that a modular MV substation can be pre-built while the interconnection study runs, and can be energised within weeks of study approval, which is a form of schedule risk arbitrage.