PDU Load
Calculate power distribution unit load and remaining capacity across connected circuits.
About PDU Load
PDU utilization compares connected equipment load against the unit's rated capacity, but continuous loads — like always-on server equipment — should be kept at or below 80% of that rating, the standard electrical derating margin that leaves headroom for inrush current and avoids nuisance breaker trips. Utilization above 80% is a warning sign even if the PDU hasn't tripped yet; above 100% risks an overload trip.
Formula
PDU utilization
utilization% = connected_watts / pdu_capacity_watts × 100
Worked example
With the default values below, PDU Load returns PDU Utilization of 60.0%. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Connected Loadminimum 0 W
- 3,000 W
- PDU Rated Capacityminimum 1 W
- 5,000 W
Results
- PDU Utilization
- 60.0%
- Status
- Within safe operating range
- Headroom to 80% Derating Threshold
- 1,000.0 W
- Headroom to Rated Maximum
- 2,000.0 W
Step by step
- 1Values used
- 2PDU utilization
- 3PDU Utilization= 60.0
- 4Status= Within safe operating range
- 5Headroom to 80% Derating Threshold= 1,000.0 W
- 6Headroom to Rated Maximum= 2,000.0 W
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why is 80%, not 100%, treated as the practical limit?
Continuous electrical loads are conventionally derated to 80% of a circuit or PDU's rating (an NEC-style convention) to leave margin for inrush current at power-on, temperature effects on conductors, and to avoid nuisance breaker trips under sustained load — the PDU's 100% rating is a hard ceiling, not a comfortable operating point.
Should I use nameplate power or measured power draw?
Nameplate (rated) power is a conservative upper bound and useful for initial planning, but measured/metered draw reflects real utilization more accurately, since equipment rarely runs at full nameplate power continuously. Use metered PDU data when available for capacity planning decisions.
How do I reduce PDU utilization?
Redistribute equipment across additional PDUs or circuits, migrate to more power-efficient hardware, or verify actual draw with a metered PDU rather than relying on conservative nameplate ratings that may overstate real load.