PDU (Power Distribution Unit): Explained in Simple Terms

Ever wondered how all those servers and network devices stay powered in a data center? The answer: Power Distribution Units (PDU).

Think of a PDU as a glorified power strip, but much more robust and designed specifically for data center environments. It takes a single power source and distributes it to multiple devices through its outlets.

Here’s why PDUs are essential:

  • Organized power delivery: Keeps your data center cabling neat and manageable.
  • Monitoring capabilities (on some models): Tracks power usage for better energy efficiency.
  • Reliable power supply: Ensures consistent performance for your critical IT equipment.

A PDU is used to distribute power, typically to networking and computer hardware housed in a rack in a data centre. A basic PDU has one input and multiple outputs, each designed to supply power to one piece of equipment.

A stable power supply is critical in data centres. Higher-spec PDUs can be monitored to check their efficiency. Here we break down the types of PDU typically used, together with their key features.

The key features of a PDU include:

  • Power Input: A PDU typically connects to a power source and can receive power from a single-phase or three-phase power source.
  • Power Output: A PDU provides power to multiple devices through its outlets, which can be configured as C13, C19, or other types depending on the equipment being powered.
  • Load Monitoring: PDUs are equipped with sensors that measure the power consumption of each outlet, enabling users to monitor power usage and identify potential issues.
  • Remote Access: Many PDUs can be accessed remotely via a network connection, allowing administrators to monitor and control power usage from a central location.
  • Redundancy: PDUs can be configured with redundant power inputs and outlets, ensuring that power is always available even in the event of a power outage or equipment failure.
  • Surge Protection: PDUs can be equipped with surge protection to prevent damage to connected equipment from power surges.
  • Mounting Options: PDUs are available in a variety of form factors, including rack-mount, wall-mount, and vertical-mount, to fit different installation scenarios.
  • User Authentication: Many PDUs feature user authentication and access control, enabling administrators to restrict access to the device and prevent unauthorized changes.
  • Environmental Monitoring: Some PDUs can monitor environmental factors such as temperature and humidity, providing administrators with valuable information to maintain optimal conditions in the data center or server room.

Power Distribution Unit (PDU)

Standard Cabinet PDUs

Comms Express stocks a wide range of standard cabinet PDUs. We have various configurations of input supply, output sockets and additional features. All PDUs are compatible with Comms Express cabinets and have a robust aluminium housing, a 3-metre input lead and an external earth facility.
The input power supply is one of the following four types:

Standard cabinet PDUs have from 4 to 16 output sockets. These sockets are either UK 13Amp or IEC C13 (to fit C14 plugs). Mixed socket PDUs are also available with a combination of C13 and C19 sockets for different equipment.

Optional features are:

  • Surge protection against power spikes
  • IE C13 integrated locking mechanism on the sockets, as protection against vibration. This holds the earth pin to protect it from being accidentally disconnected. The socket will work with equipment using any C14 or C20 plug.
  • A unit switch
  • Neon indicator
  • Branch circuits (2 x 16Amp circuits)
  • Digital ammeter to allow monitoring of the load

Advanced PDUs

Advanced PDUs allow for more sophisticated power management such as remote load monitoring. Data centre administrators can then take action to prevent power overload. In some units, individual outputs can be managed remotely, enabling sequencing during power up and power down. Comms Express stocks advanced PDUs from brands like APC, Eaton and Tripp Lite.


APC basic rack PDUs are rack-mountable and supply power to multiple devices from a single branch whip. Entry-level PDUs distribute a range of voltages at 15 Amps maximum. These PDUs have an IEC-320 C14 or C20 inlet and various outlet combinations of C13 and C19.

At the higher end of the range, APC basic rack PDUs can distribute low amperage, single phase to higher power three-phase. They come with resettable circuit breakers to help recover from overloads. These can be mounted into NetShelter enclosures for quick and easy tool-less mounting.

APC switched rack PDUs enable data centre administrators to manage power outlets remotely. During power-up, outlets can be remotely switched and time delays can be set to avoid overloads. Run-time loading can be monitored using the current metering. Alarms can be configured to alert staff to overloads. PDUs can be managed using a command line or using Struxware data centre expert.

APC metered rack PDUs provide an additional layer of protection against overloads. They enable accurate load balancing to ensure smooth running. These PDUs provide active metering for better optimisation of power across IT environments.

APC Metered by Outlet PDUs take metering to a more advanced level, by providing individual outlet power monitoring.

APC Metered by Outlet with switching PDUs combine functionality, allowing monitoring of individual outlets, with remote power on/off and power sequencing to avoid overload during power-up.

For failover environments, the APC transfer switch supplies power from two sources. If the primary source fails, the switch will also transfer power to the secondary source. The transfer doesn’t affect the connected equipment as the switch is seamless.

Eaton PDUs

Eaton provides a range of PDUs to enable accurate power distribution, monitoring and control.

At the lower end of the range, basic units can distribute power to up to 45 pieces of equipment in a high-density rack environment.

In-line metering can be added to extend the functionality of these basic units. At the high end of the range, both metered and switched outlets are available.

Eaton advanced monitored PDUs allow monitoring of individual outlets, a group of outlets or the full PDU. Power, voltage and amperage are monitored, together with temperature and humidity.
Eaton switched PDUs enable remote control of the unit, including rebooting. Daisy chaining up to 8 PDUs using one IP address reduces the networking cost, this approach is required when using primary and secondary power feeds.

Eaton G3 metered input PDUs introduce phase branch level metering, which enables load balancing.

Metered output PDUs allow administrators to understand power consumption at the individual equipment level, including when supplied by primary and secondary feeds.

Finally, Eaton G3 managed PDUs combine the features of metering and switching, allowing remote management and reboot.

Tripp Lite PDUs

Tripp Lite manufactures a range of PDUs – of similar functionality to APC. Models include basic, switched, metered, auto-transfer and monitored.
The Tripp Lite HotSwap PDU allows for the maintenance of a UPS without affecting connected equipment.

What Is PDU? – Conclusion

As we can see, PDUs come in many forms, from basic functions to advanced monitoring. Whether you need basic or advanced setups, Comms Express is your one-stop shop for all your PDU needs. If you’re struggling to work out which PDU is for you, then have a look at our review of the Top 10 PDUs.