What voltage does power run at inside an AI data center?

Power typically arrives at transmission voltage, steps down to medium voltage (13.8 kV or 34.5 kV) for distribution across the site, steps down again to 480V three-phase at unit substations near each data hall, and finally steps down to 208V through PDUs before reaching the rack.

What is the difference between a PDU and busway in a data center?

A PDU (power distribution unit) provides circuit breakers, metering, and monitoring at the point where 480V power is stepped down and distributed to racks, either via cable whips or busway. Busway is a rigid or flexible overhead conductor track that can be tapped at any point along its length, letting an operator add or move a rack power connection without pulling new cable from the PDU.

Why does a data center use two separate power paths (A and B)?

Running two electrically independent power paths from the substation to the rack means a fault or maintenance event on one path never interrupts power, since dual-corded servers draw from both paths simultaneously and can run fully on either one alone. This redundant A/B architecture is the basis for N+1 and 2N redundancy ratings.

Why is medium voltage used to distribute power across a data center campus?

Medium voltage (13.8-34.5 kV) keeps current, and therefore conductor size and resistive losses, manageable across the long distances a large campus can span. Distributing directly at the lower 480V used inside a data hall would require impractically large conductors and waste significant power as heat over those distances.

Engineering·11 min read·September 19, 2026

⚡ AI Data Center Power Distribution Explained

How power actually moves through an AI data center after it enters the site — medium-voltage switchgear, unit substations, UPS systems, PDUs, and busway — and why the distribution architecture is built around redundant, electrically independent A and B paths.

🎓Data Center Engineering Basics — Start to Finish (Full Access)

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From the Utility Meter to the Rack: The Full Distribution Chain

Power distribution in an AI data center is a series of deliberate step-downs, each one trading a lower voltage for higher current, moving from the utility interconnection all the way to the individual server power supply. Understanding this chain matters because a problem or a design decision at any single stage — undersized medium-voltage switchgear, an inadequately-rated busway run, a UPS sized for yesterday's rack density — can bottleneck the entire facility's usable capacity, regardless of how much power the utility connection itself can deliver. The full path, at a glance: utility service → main substation (steps down to medium voltage) → medium-voltage feeders to unit substations near each hall → 480V distribution → UPS → PDUs or busway → rack. See AI Data Center Electrical Design — Complete Guide for the full picture including generation and backup systems; this article focuses specifically on the distribution path itself.

Topics covered

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