LED Driver Load Calculator

An LED Driver Load Calculator converts a block of LED drivers into the electrical load used for early branch-circuit or feeder review. It produces Total driver watts, Total driver load in VA, Adjusted driver load in VA, and Circuit current in amperes.

The circuit-current result provides the starting load value for conductor ampacity review, overcurrent protective-device selection, panel schedule loading, voltage-drop review, and raceway planning. It does not select an AWG or kcmil conductor size, account for conductor adjustment factors or correction factors, or establish the final rating of a branch circuit.

LED drivers are commonly specified in watts and power factor. Circuit loading, however, must account for apparent power in volt-amperes when current is calculated. A lower power factor increases VA and current for the same connected driver watts.

Driver VA and Continuous Load

Enter Driver watts as the input watts of one LED driver and Driver quantity as the number of identical drivers in the load block.

The calculator first determines connected driver watts:

\(\displaystyle \text{Total driver watts} = \text{Driver watts} \times \text{Driver quantity}\)

It then converts connected watts to apparent power using Power factor:

\(\displaystyle \text{Total driver load (VA)} = \frac{\text{Total driver watts}}{\text{Power factor}}\)

Power factor is entered as a decimal value, such as 0.90. A 96 W driver with a 0.90 power factor draws approximately 106.7 VA, not 96 VA. The difference represents the apparent-power demand used for current conversion.

The calculator applies the entered Continuous multiplier to the total driver VA:

\(\displaystyle \text{Adjusted driver load (VA)} = \text{Total driver load} \times \frac{\text{Continuous multiplier}}{100}\)

A 125% multiplier converts 1,920 VA of driver load into 2,400 VA of adjusted driver load. The multiplier is an input, so it should match the applicable project design basis and electrical-code determination rather than being assumed from the connected load alone.

Circuit Current

System voltage converts adjusted VA into circuit current. Select Phase as either Single-phase or balanced three-phase so the calculator applies the corresponding current math.

For the single-phase selection:

\(\displaystyle \text{Circuit current} = \frac{\text{Adjusted driver load (VA)}}{\text{System voltage (V)}}\)

For a balanced three-phase load, current is based on the balanced three-phase VA relationship rather than the single-phase division shown above. The selected phase arrangement must match the actual supply and the way the LED drivers are distributed across the system.

The resulting Circuit current is the load current for the entered driver block. It can be carried into a conductor sizing workflow, voltage-drop calculation, panelboard load schedule, or feeder load review. When several lighting groups have different driver ratings, power factors, or supply voltages, calculate each group separately before combining loads.

Calculation Example

The following values use the LED driver load workflow:

Input	Value
Driver watts	96 W
Driver quantity	18 count
Power factor	0.9 PF
Continuous multiplier	125%
System voltage	120 V
Phase	Single-phase

Total driver watts

\(\displaystyle 96\text{ W} \times 18 = 1{,}728\text{ W}\)

Total driver watts = 1,728 W

Total driver load

\(\displaystyle \frac{1{,}728\text{ W}}{0.9} = 1{,}920\text{ VA}\)

Total driver load = 1,920 VA

Adjusted driver load

\(\displaystyle 1{,}920\text{ VA} \times 1.25 = 2{,}400\text{ VA}\)

Adjusted driver load = 2,400 VA

Circuit current

\(\displaystyle \frac{2{,}400\text{ VA}}{120\text{ V}} = 20\text{ A}\)

Circuit current = 20 A

Conductor and Installation Review

A 20 A calculated circuit load is not, by itself, a conductor or breaker selection. Final branch-circuit or feeder design requires the actual installation conditions, including conductor ampacity, AWG or kcmil size, terminal rating, insulation temperature rating, and any applicable adjustment factor or correction factor.

Review the installation separately for:

• The driver nameplate input watts and listed power factor, rather than fixture output watts or lamp wattage.
• The actual voltage available at the lighting circuit, including whether the system is single-phase or balanced three-phase.
• Driver inrush current, harmonics, and manufacturer installation instructions where they affect equipment selection or circuit performance.
• Current-carrying conductors in the raceway or cable, ambient-temperature conditions, and resulting conductor ampacity.
• Branch-circuit voltage drop and feeder voltage drop, especially on long lighting runs or installations with concentrated driver loads.
• Raceway fill, box fill, conductor bending space, disconnecting means, and equipment grounding requirements.
• The final load calculation, overcurrent protection, and installation acceptance requirements of the AHJ.

The calculator establishes the electrical load arithmetic for the entered LED drivers. The final design must be based on the installed equipment, conductor system, protection, and applicable project and code requirements.

Related calculations: Lighting Load Calculator, Lighting Layout Calculator, Electricity Cost Calculator.