Server Rack PDU Guide: Basic vs Metered vs Switched, Single-Phase vs 3-Phase (2026)

A rack full of servers is only as reliable as the power strip feeding it — and "power strip" undersells what a proper rack PDU (Power Distribution Unit) actually does. Getting the PDU tier wrong either wastes money on features you'll never use, or leaves you blind when a server trips a breaker at 2am.

The four PDU tiers

• Basic — just distributes power, no monitoring. Fine for a small rack you can physically check.
• Metered — adds a local or remote display of total load (amps/kW), so you know how close you are to tripping the breaker before it happens.
• Monitored — metered, plus network access so you can check load and get alerts remotely, sometimes down to the individual outlet.
• Switched — full remote control: power-cycle individual outlets over the network, without walking to the rack. The tier that matters most once a rack has more than a handful of servers in a colo or a remote office.

Single-phase vs 3-phase

Single-phase PDUs are simpler and standard for smaller racks. 3-phase PDUs deliver more usable power through the same rack footprint and physical circuit, and are the norm once a rack is genuinely dense — multiple dual-PSU servers, a SAN array, and networking gear all in one enclosure. If your electrician is already running 3-phase to the room, it's usually worth feeding the rack that way from day one rather than retrofitting later.

Sizing basics before you buy

• Add up the rated (not typical) power draw of every device going in the rack, then leave real headroom — don't run a PDU near its rated max continuously.
• If any server has redundant (dual) power supplies, feed each PSU from a different PDU — otherwise the redundancy is pointless, since one PDU failure takes the server down anyway.
• Match the outlet type (C13/C14, C19/C20) to what your servers' power cables actually use — higher-draw servers often ship with C19/C20 cords, not the smaller C13/C14.

Every server we supply lists its actual PSU wattage and connector type, so PDU/rack planning is straightforward before the hardware arrives. Need help sizing power for a new rack? Talk to us via our AMC & services team, or browse current tested inventory.