Panel load and spare-capacity equations
Demand power is converted to current before comparing with the entered panel main rating.
Pdemand = Pconnected × FdemandI3φ = 1000P/(√3VPF)I1φ = 1000P/(VPF)Ispare = Imain − IdemandUnbalance% = max|Iphase−Iavg|/Iavg × 100where:
- Fdemand
- Entered demand factor
- Ispare
- Arithmetic spare-current screen[A]
Positive arithmetic spare does not by itself approve added load.
How to use the Electrical Panel Load and Spare Capacity Calculator
Calculate panel kVA, current, utilization, spare amperes, spare kVA, phase-load unbalance, and expansion impact from entered demand loads. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Balanced calculated load for kW-to-current conversion Main rating represents usable panel ampere capacity Optional phase readings are simultaneous A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Balanced calculated load for kW-to-current conversion
- Main rating represents usable panel ampere capacity
- Optional phase readings are simultaneous
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Main ampere rating alone does not establish feeder, busbar, breaker or service capacity. Measured demand methods, continuous loads, harmonics, neutral current and code rules require separate review. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Balanced calculated load for kW-to-current conversion
- Main rating represents usable panel ampere capacity
- Optional phase readings are simultaneous
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Main ampere rating alone does not establish feeder, busbar, breaker or service capacity.
- Measured demand methods, continuous loads, harmonics, neutral current and code rules require separate review.