Power Distribution Units (PDU)

Category overview

A Power Distribution Unit is the rack equivalent of a power strip, with proper IEC outlets, a strong mechanical design and, in many models, monitoring or switching electronics. Choosing the right PDU is a matter of matching outlet count and current rating to the rack's load, and deciding how much remote management is needed.

What this category covers

Vertical (zero-U) and horizontal (1U) rack PDUs in basic, metered, monitored and switched configurations, with outlet counts from a few to several dozen. Different input plug types are available to match the supply at the rack.

How to choose a PDU

Pick the right tier of management

Basic PDUs only distribute power. Metered units have a local display showing total current. Monitored units report per-outlet or per-bank figures over the network. Switched units let each outlet be turned on or off remotely, which is the main feature for unattended sites and remote troubleshooting.

Match outlet count and outlet type

Count the equipment in the rack, then add headroom for future growth. Most server gear uses C13 inlets; high-current devices use C19. A PDU with a mix of both, in the right ratio, avoids forcing adapters or step-up cables.

Check the input plug and total current

The input plug must match the rack's feed: 16 A, 32 A, single-phase or three-phase, with the correct country plug. The total current rating sets the maximum sum across all outlets. Going close to the rated maximum without margin is unsafe and trips the breaker on small surges.

Consider form factor and cable management

Vertical zero-U PDUs mount on the side of the rack and free up rack units for equipment. Horizontal PDUs occupy 1U or 2U and are easier to access from the front. Cable management trays and clips reduce strain on the IEC plugs and keep airflow clean.

Key features to compare

Per-outlet metering

Per-outlet current and energy figures are useful for capacity planning and identifying problem devices. They cost more than bank-level metering but pay back in larger or growing racks.

Daisy-chaining and overall management

Some managed PDUs can share a single network connection across several units in a row. This simplifies cabling at the top of the rack and reduces the number of management ports consumed.

What to check before buying

• Does the input plug match the rack's feed (current rating, phases, country plug)?
• Are there enough C13 and C19 outlets, in the right mix, for current and planned equipment?
• Is local monitoring enough, or is remote per-outlet switching required?
• Will the PDU sit vertically (zero-U) or horizontally, and does the rack have space for that?
• Is the management interface compatible with the existing monitoring system?

Frequently asked questions

Do I really need a managed PDU?

For a single rack with on-site staff, a basic PDU is often enough. For racks at remote sites, in shared cabinets, or in growing setups where capacity has to be tracked over time, a metered or switched PDU pays back quickly. The break-even point is usually as soon as a single avoided site visit covers the price difference.

What is a zero-U PDU?

A zero-U PDU mounts vertically on the side of the rack and does not occupy any rack units of vertical space. This frees space for servers and is the standard layout in dense racks. Horizontal PDUs occupy 1U or 2U and are still common in smaller cabinets.

Can a PDU replace a UPS?

No. A PDU only distributes the power it receives. If the input fails, every outlet on the PDU goes dark immediately. Backup power is the role of a UPS, which in many setups feeds the PDU.

How do I size the total current rating?

Add the running current of the connected equipment, then leave around 20 to 30 percent headroom for surges and future growth. Running close to the rated maximum reduces resilience and trips the breaker on normal load swings.

What is the difference between switched and outlet-switched PDUs?

Both let outlets be turned on and off remotely. Switched PDUs typically allow individual outlet control. Some lower-cost models only allow switching at the bank level, where a group of outlets shares one relay. For per-outlet reboot of specific devices, full per-outlet switching is required.