Comparing Data Center Power Distribution Architectures

A Comprehensive Guide from Schneider Electric’s Data Center Science Center

The rapid evolution of IT equipment has fundamentally changed how power needs to be delivered in modern data centers. Traditional distribution architectures, developed decades ago, often struggle to meet the demands of high density, frequent equipment refreshes, and the need for flexibility. Schneider Electric’s White Paper 129, "Comparing Data Center Power Distribution Architectures," provides a detailed analysis of five common approaches, helping engineers and facility managers select the optimal strategy for their specific needs. This article summarizes the key findings from this essential guide.

Introduction

Many existing data centers utilize power distribution architectures that were developed approximately 40 years ago. However, dramatic changes in how power is utilized have challenged this traditional model. Modern IT equipment has introduced several key challenges summarized in Table 1:

Improved systems that address these challenges allow IT racks to be installed or changed without new wiring, distribute power overhead, support rack densities up to 30 kW, and include branch circuit power monitoring.

The Five Architectures Compared

The paper evaluates five power distribution architectures, ranging from traditional to highly modular:

1. Panelboard distribution
2. Field-wired PDU distribution
3. Factory-configured PDU distribution
4. Overhead / underfloor modular distribution (busway)
5. Floor-mount modular power distribution

Panelboard Distribution

In this approach, power is distributed to wall-mounted panelboards (typically 1.5 kVA to 75 kVA). Individual branch circuits are cut, terminated, and connected in the field by the electrical contractor, running either overhead in cable trays or under the raised floor.

Best used for: Smaller installations, when lowest first cost is a priority, and when IT changes are not frequent.

Traditional PDU Distribution – Field-Wired

Main data center power is distributed to multiple PDUs (50-500 kVA) located throughout the IT space. The electrical contractor plays a large role in engineering this solution, with significant wiring work done onsite, including cutting, terminating, and connecting each individual branch circuit.

Best used for: When low first cost is a priority and when IT changes are not likely.

Traditional PDU Distribution – Factory-Configured

Much of the field-wiring work is done in a controlled factory. The PDU is configured with factory-assembled branch breakers and power cables pre-cut and terminated to the required length and ampacities.

Best used for: When the data center plans to scale at the pod level, when portability is required, or when low first cost is still a priority.

Modular Distribution – Busway

Busway is generally installed overhead (or underfloor) over IT equipment rows. IT enclosures connect via plug-in units with breaker boxes.

Best used for: Space-constrained rooms, large facilities with a well-defined IT row layout, high confidence in final IT load, and high-frequency IT equipment turnover.

Modular Distribution – Floor-Mount

Modular PDUs have a backplane into which pre-terminated circuit breaker modules are installed, eliminating on-site wire termination.

Best used for: Data centers with uncertain growth plans, when room shape or ceiling height is constrained, when IT personnel want to reconfigure circuits without third parties, when speed of deployment is a priority, and for retrofitting existing data centers.

Key Comparisons and Guidance

Reliability & Safety Comparison

Cost Comparison

Capital Cost (per watt):

• Panelboard: $0.15 – $0.30
• Field-wired PDU: $0.20 – $0.40
• Factory-configured PDU: $0.30 – $0.50
• Busway modular: $0.40 – $0.60
• Floor-mount modular: $0.40 – $0.70

Operating Cost: Underfloor cabling causes interference with airflow, reducing cooling efficiency. Overhead distribution avoids this issue.

Agility Comparison

Conclusion

The paper concludes that modern data center demands often favor modular distribution approaches, which offer greater flexibility, manageability, reliability, and efficiency compared to traditional architectures, despite a potentially higher first cost.

• Panelboard and field-wired PDU distribution are best when low first cost is the highest priority and when IT changes are unlikely.
• Factory-configured PDU distribution is optimal when portability and future pod-based scaling are important, while still prioritizing low first cost.
• Busway is ideal when floor space is a constraint, the IT layout is well-defined, and there is high confidence in the final capacity.
• Floor-mount modular PDU distribution is best suited for data centers with uncertain growth plans, those requiring flexibility in placement, and for retrofitting projects.

Download the Full White Paper

This overview is based on White Paper 129: "Comparing Data Center Power Distribution Architectures" from Schneider Electric’s Data Center Science Center. The full document provides a deeper analysis, including detailed tables, figures, and application-specific guidance.

The white paper is available to download for free directly from Schneider Electric:

Download White Paper 129 (PDF)

Disclaimer: This article provides a summary of a third-party white paper. While efforts have been made to accurately represent the content, please refer to the official Schneider Electric document for complete technical details. Final design decisions remain the responsibility of qualified professionals.