Frequently asked PDU questions

1. What does PDU stand for?

PDU stands for Power Distribution Unit. It is the heart of the power supply within a server rack or other IT installation. A PDU ensures that electrical power from the main supply is distributed in a controlled manner to all connected servers, switches, storage systems and other critical hardware.

In a data centre environment, a PDU is much more than just a power strip:

• Reliable power distribution: A PDU ensures that each device receives the correct voltage and current, without overloads or unnecessary losses.

• Continuity of IT services: By using PDUs with monitoring and switching capabilities, operators can prevent outages and respond more quickly when intervention is required.

• Intelligent energy management: Modern PDUs measure power consumption at rack, branch or outlet level. This provides data centre managers with the insights they need to plan capacity, improve energy efficiency and meet compliance requirements.

• Integration with IT infrastructure: Advanced PDUs communicate directly with DCIM and BMS systems, making energy data an integral part of overall data centre monitoring.

2. What is a PDU?

A PDU is a professional power distribution device specifically designed for use in data centers and server rooms. It distributes power efficiently and often includes additional features such as power monitoring and switching capabilities.

3. Why use a PDU?

PDUs provide a safe, efficient and organised way to distribute power within a server rack. They help manage energy consumption, optimise space and offer capabilities such as monitoring and switching.

In high-density racks running AI servers, HPC clusters or cloud infrastructure, power levels can quickly reach tens of kilowatts per rack. Without a reliable PDU, a power-related issue can lead to downtime, data loss and significant costs.

For this reason, a PDU has become an integral part of critical IT infrastructure:

• They ensure the safe distribution of high power loads.

• They enable remote switching, allowing servers to be powered on or off in a controlled manner.

• They provide data that can be used for capacity planning, predictive maintenance and energy reporting.

• They support sustainability and energy optimisation, which are increasingly important in modern data centres.

4. What is the difference between a power strip and a PDU?

A power strip is simply an extension lead with multiple sockets, while a PDU is designed for professional use in racks, offering options for monitoring, switching, and other advanced features.

5. What’s inside a PDU?

A PDU typically contains:

• An inlet (for power input)
• A series of outlets (for power output)
• Depending on the type, internal components for monitoring, switching, or surge protection.

6. What is a PDU inlet?

The PDU inlet is the connection point where power enters the PDU. This can be a fixed power cable or an inlet connector, such as a C14 or C20 connector.

7. What types of PDUs are there?

There are several types of PDUs, including:

• Basic: No monitoring
• Basic Plus: Upgradeable to monitoring
• Metered: Monitoring per phase and circuit breaker
• Monitored: Monitoring per phase, circuit breaker, and outlet
• Switched: Monitoring with switching capabilities per outlet
• Managed: Full monitoring and switching per outlet
• Inline Meter: Monitoring for existing PDUs

8. What does a metered PDU mean?

A metered PDU provides power monitoring at the level of phases and circuit breakers, helping manage energy consumption.

9. How does an intelligent PDU work?

An intelligent PDU (such as a Managed or Monitored PDU) has sensors and communication modules that enable real-time monitoring and management. Users can remotely check and control data such as power consumption, voltage, and current.

10. Do PDUs have circuit breakers?

Yes, many PDUs come with circuit breakers to protect connected equipment from overload.

11. What’s the difference between a UPS and a PDU?

• UPS (Uninterruptible Power Supply): Provides emergency power and protects against voltage spikes and power outages.
• PDU: Distributes power efficiently to multiple devices in a rack.

12. Do PDUs have surge protection?

Some PDUs offer surge protection, but this is not standard on every PDU. Be sure to check the device’s specifications.

13. How many PDUs do I need in a rack?

The number of required PDUs depends on the power consumption of your equipment, the desired redundancy, and the layout of your rack. In professional data centre environments, it is standard to install at least two PDUs per rack: one on the A feed and one on the B feed. This ensures power redundancy – if one path fails, your equipment continues running on the other feed.

In high-density or critical infrastructure racks, a C feed may also be used. In some cases, multiple PDUs per feed are installed to support both horizontal and vertical equipment distribution.

14. Where should I mount the PDU in the rack?

PDUs are typically mounted on the side or rear of a rack. This optimizes accessibility and saves space.

15. What does a rack PDU do?

A rack PDU distributes power to the equipment within a server rack. Depending on the type, it may also provide monitoring, switching, and remote management.

16. What is a floor PDU?

A floor PDU is a larger power distribution unit used to distribute power across multiple racks or zones within a data center.

17. What is the voltage of a PDU?

The voltage varies depending on the PDU type and region. In Europe, the standard voltage is 230V, but there are also PDUs for 400V or other voltages.

18. Which PDU do I need?

The choice depends on your needs:

• Basic: No monitoring. This type of PDU is ideal for simple applications where only power distribution is required, without the need for monitoring or additional features. It is suitable for small offices, non-critical IT systems, or equipment with predictable power consumption.
• Basic Plus: Upgradeable to energy monitoring. This PDU is suitable for situations where you don’t currently need monitoring but want the flexibility to add it later. It is useful in growing IT environments where future energy management may play a role.
• Metered: Energy monitoring per phase and circuit breaker. This PDU is necessary in environments where insight into total energy consumption is essential, such as medium-sized data centres or server rooms. It helps with capacity management and identifying peak loads.
• Monitored: Energy monitoring per phase, circuit breaker, and outlet. This type of PDU is suitable for data centres and IT environments where detailed insights into energy consumption per device are required. It is useful for detailed reporting, cost management, and energy-saving initiatives.
• Switched: Energy monitoring per phase and remote switching per outlet. This PDU is ideal for situations where you want to be able to restart or switch off equipment remotely. It is suitable for businesses with multiple locations or data centres where physical access is limited.
• Managed: Full energy monitoring and remote switching per outlet. This type of PDU is essential in high-performance data centres and critical IT environments. It provides maximum control over energy consumption and device management, improving operational efficiency and uptime.
• Inline Meter: Energy monitoring for existing PDUs without monitoring. This is an excellent option if you already have existing PDUs without energy monitoring but need insight into power usage. It is suitable for upgrading older racks or equipment with basic PDUs without replacing them entirely.

19. Is a PDU necessary?

Yes, especially in professional environments like data centers, where efficiency, safety, and monitoring are essential.

20. Who manufactures PDUs?

Many companies manufacture Power Distribution Units (PDUs), but there are significant differences in how they design and supply them.

Some manufacturers offer only a fixed portfolio of standard models with limited configuration options. Others, like Schleifenbauer, design and manufacture build-to-order Rack PDUs that are fully customised to meet the exact requirements of each project.

As a European PDU manufacturer based in the Netherlands, Schleifenbauer develops and produces intelligent Rack PDUs for enterprise data centres, colocation providers, hyperscalers, AI infrastructure and HPC environments.

Every PDU is built to order and can be configured with virtually any combination of:

• Single-phase or three-phase power
• Input ratings from 10A to 63A
• A wide range of outlet types (IEC, Schuko, BS1363, GST18, Type E and more)
• Basic, Metered, Monitored, Switched and Managed functionality
• Input, branch and outlet-level energy monitoring
• Remote outlet switching
• Environmental sensors
• Colour coding and custom labelling
• Customer-specific outlet layouts
• Hybrid or Ethernet network architectures

Unlike manufacturers that rely on a limited catalogue of standard products, Schleifenbauer manufactures every Rack PDU to customer specifications. This allows data centre operators, OEMs and system integrators to order a power distribution solution that exactly matches their infrastructure without compromising on functionality.

Combined with licence-free EnerTree DCEM Software, open APIs and short production lead times, Schleifenbauer provides a future-proof power distribution platform without vendor lock-in.

21. What does DCEM mean?

DCEM stands for Data Centre Energy Management. It is software that helps data centres gain insight into, analyse and optimise the energy consumption of IT equipment and infrastructure. DCEM software collects measurement data from sources such as PDUs and inline meters and translates this data into actionable information for energy management, cost control and compliance.

22. What is DCEM software and what is it used for in data centres?

DCEM software is energy management software for data centres. It is used to monitor real-time and historical energy data at rack, PDU, circuit or outlet level. Data centre operators use DCEM software to reduce energy waste, improve capacity planning, generate reports and comply with regulations such as energy audit requirements.

23. What is the difference between DCEM software and DCIM software?

DCIM (Data Centre Infrastructure Management) focuses on the entire data centre infrastructure, including space, cooling, assets and workflows.
DCEM (Data Centre Energy Management) software focuses specifically on energy and power management. DCEM is often simpler, faster to deploy and more scalable when energy insight and energy reporting are the primary requirements.

24. What data does DCEM software use?

DCEM software uses measurement data from sources including:

• Managed and monitored PDUs
• Inline meters
• Power measurements per input, branch and outlet
• Environmental or status sensors

This data is used for real-time monitoring, trend analysis, alarms and energy reporting per rack, customer or location.

25. Is DCEM software suitable for energy compliance and reporting?

Yes. DCEM software is widely used for energy compliance, audits and reporting. It helps data centres demonstrate energy consumption, efficiency and CO₂-related targets. DCEM supports reporting for both internal analysis and external compliance requirements, without the need for complex DCIM systems.

26. What is stranded capacity in a data centre?

One of the biggest hidden costs in modern data centres is stranded capacity.

Stranded capacity occurs when available power cannot be used efficiently because there is insufficient insight into the actual power consumption of each rack, circuit or outlet.

For example:

• A rack is designed for 30 kW.
• The installed equipment actually uses only 21 kW.
• Because there is no detailed power monitoring, operators reserve the full 30 kW.
• The remaining 9 kW becomes stranded capacity that cannot safely be allocated to new IT equipment.

With outlet-level monitoring and real-time power data from intelligent Rack PDUs, operators can safely reclaim unused capacity, postpone expensive infrastructure expansions and increase rack utilisation.

Schleifenbauer Managed PDUs and EnerTree DCEM Software provide real-time power data that helps identify stranded capacity throughout the data centre.

27. How can intelligent PDUs reduce stranded capacity?

Traditional power planning is based on assumptions.

Intelligent Rack PDUs replace assumptions with real-time measurements.

By monitoring:

• Voltage
• Current
• Real Power
• Apparent Power
• Power Factor
• Energy (kWh)
• Outlet-level consumption

data centre operators gain an accurate picture of actual rack utilisation.

This enables:

• Higher rack density
• Better AI workload planning
• Faster customer onboarding
• Delayed infrastructure upgrades
• Lower operational costs

28. What is rack telemetry?

Rack Telemetry is the continuous collection of operational data from every server rack.

Modern rack telemetry combines:

• Rack PDU measurements
• Environmental sensors
• Energy monitoring
• Alarm management
• Historical trends

Rack telemetry enables operators to detect abnormal behaviour before failures occur and forms the basis for predictive maintenance.

Schleifenbauer Rack PDUs stream live telemetry data to EnerTree DCEM Software and third-party DCIM platforms through REST API, SNMP and Modbus TCP.

29. What is power observability?

Power Observability means having complete visibility into how electrical power flows through a data centre.

Instead of only monitoring total facility power, operators monitor:

• Incoming power
• Branch circuits
• Individual outlets
• Individual servers

Power observability helps improve uptime, optimise capacity planning and identify hidden inefficiencies.

30. What is rack-level power monitoring?

Rack-level power monitoring provides detailed insight into the energy consumption of every individual server rack.

Unlike building-level monitoring, rack-level monitoring helps identify:

• Overloaded racks
• Underutilised racks
• Capacity bottlenecks
• Energy waste
• Unbalanced phases

This information is essential for AI clusters, HPC environments and colocation data centres.

31. What is outlet-level power monitoring?

Outlet-level monitoring measures the power consumption of every connected device individually.

This allows operators to:

• Identify zombie servers
• Detect abnormal consumption
• Allocate energy costs per customer
• Improve capacity planning
• Remotely switch equipment

Outlet-level monitoring is increasingly becoming a requirement in colocation and AI data centres.

32. What are zombie servers?

Zombie servers are servers that consume power but perform little or no useful work.

Research estimates that a significant percentage of servers in enterprise environments are underutilised while still consuming electricity and cooling capacity.

Using outlet-level monitored Rack PDUs, operators can identify these systems and decide whether they can be consolidated, repurposed or switched off.

This reduces energy costs and frees valuable rack capacity.

33. What is AI-ready power infrastructure?

AI servers consume significantly more power than traditional enterprise servers.

Modern AI racks often require:

• High-density power distribution
• Three-phase PDUs
• Outlet-level monitoring
• Real-time telemetry
• Remote management
• High ambient operating temperatures

Schleifenbauer PDU 5.0 has been developed specifically for high-density AI, HPC and GPU environments.

34. What is vendor lock-in in data centre power management?

Vendor lock-in occurs when a data centre becomes dependent on one manufacturer for hardware, software and future expansions.

This often results in:

• Higher operating costs
• Expensive software licences
• Limited integration possibilities
• Reduced flexibility

Schleifenbauer avoids vendor lock-in through open APIs, standard protocols and licence-free EnerTree DCEM Software.

35. Why are recurring licence fees becoming a problem?

Many intelligent PDUs now require annual software subscriptions.

Over the lifetime of a data centre, these recurring costs can exceed the purchase price of the hardware.

Schleifenbauer includes EnerTree DCEM Software without recurring licence fees, reducing the total cost of ownership while giving operators full control over their energy data.