| Basic PDU | Distributes electrical power from one upstream source to multiple IT equipment outlets. | No built-in electrical measurement or remote monitoring. Status is generally limited to a power indicator and circuit protection status. | No individual outlet switching. Power is normally available whenever the upstream supply and PDU circuit are energized. | Commonly available in single-phase or three-phase configurations, with input ratings often ranging from approximately 10 A to 60 A depending on the installation and local electrical standard. | Stable server racks where low cost and simple power distribution are the main requirements. | Simple installation, low purchase cost, high reliability, and minimal configuration. | It cannot identify circuit overload trends, measure rack consumption, or remotely reboot equipment. |
| Metered PDU | Distributes power while displaying the electrical load drawn by the complete PDU or by an upstream circuit. | Usually provides local readings such as voltage, current, power, apparent power, power factor, and energy consumption. Remote access may not be included. | No individual outlet switching. The PDU is intended for measurement rather than remote power control. | Measurements may be shown on a local display in amperes, volts, watts, volt-amperes, power factor, or kilowatt-hours, depending on the model. | Racks that need local load visibility without the cost or complexity of network management. | Helps operators verify load balance, detect rising consumption, and reduce the risk of circuit overloading. | Local readings may not be available to a central data-centre management platform unless a network interface is provided. |
| Monitored PDU | Measures rack-level electrical conditions and communicates the data to a remote monitoring or management system. | Typically reports voltage, current, active power, apparent power, power factor, energy, phase load, and alarm conditions through a network interface. | Normally does not switch individual outlets. Its main purpose is measurement, alerting, and capacity management. | May support Ethernet-based management, web interfaces, SNMP, environmental sensors, event logs, and configurable high- or low-load thresholds. | Data centres that require remote capacity planning, centralized alerts, and energy reporting. | Provides real-time visibility, early overload warnings, and useful data for rack consolidation and efficiency analysis. | Network configuration and cybersecurity controls are required. Monitoring accuracy and measurement points should be checked before deployment. |
| Switched PDU | Provides monitored power distribution with remote control of individual outlets or outlet groups. | Usually includes current, voltage, power, energy, power factor, outlet status, alarms, and event logging through a network interface. | Allows authorized users to turn outlets on, turn them off, cycle power, sequence startup, and sometimes set outlet-level access permissions. | May include outlet-level metering, remote reboot functions, outlet sequencing, delayed startup, and load-shedding policies. | Remote facilities, unmanned racks, colocation environments, and equipment that occasionally requires controlled power cycling. | Enables remote recovery, reduces site visits, and supports controlled startup to limit inrush current. | Incorrect switching can interrupt critical equipment. Outlet labeling, access control, and startup sequencing are essential. |
| Automatic Transfer Switch (ATS) PDU | Supplies connected equipment from a preferred power source and automatically transfers the load to a secondary source if the preferred source fails. | May monitor input voltage, frequency, source availability, transfer status, current, and output load. Monitoring functions vary by design. | Uses an internal transfer mechanism rather than ordinary outlet-by-outlet switching. Transfer occurs when the alternate source meets the required electrical conditions. | Requires two independent input sources. Transfer time is commonly measured in milliseconds, but the actual value depends on the design and source conditions. | Single-corded servers and networking equipment that need source redundancy without two separate power supplies. | Improves availability by using two independent feeds and can protect equipment from the loss of one upstream source. | Both inputs must be correctly rated and preferably supplied by independent circuits or power paths. An ATS PDU does not replace an uninterruptible power supply. |
| Three-Phase PDU | Distributes three-phase electrical power efficiently to high-density racks or multiple single-phase loads. | Depending on the model, it may provide phase-level voltage, current, power, energy, power factor, and imbalance measurements. | May be basic, metered, monitored, or switched. Three-phase describes the electrical supply format rather than a specific management function. | Common configurations include three-phase input with single-phase outlets or three-phase input with three-phase outlets. Phase balancing is important to use capacity effectively. | High-density computing, large server rooms, and facilities designed around three-phase distribution. | Supports higher power capacity, improves distribution efficiency, and can reduce the number of upstream circuits and cables. | Installation should follow local electrical codes. Uneven phase loading can reduce available capacity and create avoidable electrical stress. |
| High-Density PDU | Delivers a high amount of power to racks containing dense computing equipment, including accelerated computing systems. | Often includes detailed circuit, phase, or outlet-level measurements, alarms, and integration with data-centre infrastructure management software. | May be basic, monitored, or switched. High power capacity does not automatically mean that remote outlet control is available. | May use higher-current inputs, three-phase distribution, compact outlet spacing, and multiple branch circuits. The allowable capacity depends on voltage, current rating, phase configuration, and derating requirements. | High-performance computing and other racks with substantially higher power demand than conventional enterprise servers. | Supports greater rack power density and can provide more accurate visibility into rapidly changing electrical loads. | Cooling capacity, connector compatibility, short-circuit protection, cable routing, and upstream distribution must be assessed together with the PDU rating. |
| Rack-Mounted PDU | Mounts vertically or horizontally inside or beside a server cabinet to distribute power close to the equipment. | Monitoring depends on the selected model and may range from no measurement to outlet-level network monitoring. | Control depends on the product category; a rack-mounted PDU may be basic, metered, monitored, switched, or ATS-based. | Common physical formats include vertical zero-U mounting and horizontal 1U or 2U mounting. Outlet types and input connectors must match the installed equipment and facility supply. | Standard server cabinets, network racks, and structured data-centre deployments. | Uses rack space efficiently, shortens equipment power-cable runs, and simplifies cabinet-level distribution. | The cabinet dimensions, mounting position, outlet spacing, cable bend radius, and total connected load should be verified before installation. |
