Calculator Inputs
Choose a method, enter site values, and calculate apparent power for temporary distribution, feeders, and generator planning.
Plotly Graph
This chart compares connected load, adjusted demand, design kVA, and recommended generator size.
Example Data Table
These example construction loads show how different site equipment contributes to total apparent power.
| Equipment | Voltage (V) | Current (A) | Phase | Power Factor | Apparent Power (kVA) |
|---|---|---|---|---|---|
| Tower Lighting String | 230 | 12 | Single | 0.95 | 2.760 |
| Concrete Vibrator | 230 | 8 | Single | 0.90 | 1.840 |
| Portable Welder | 400 | 18 | Three | 0.82 | 12.471 |
| Material Hoist | 400 | 28 | Three | 0.86 | 19.399 |
| Batch Mixer | 400 | 22 | Three | 0.88 | 15.242 |
| Example Total | 51.712 kVA | ||||
Formula Used
S (kVA) = V × I ÷ 1000
S (kVA) = √3 × V × I ÷ 1000
S (kVA) = P (kW) ÷ PF
S (kVA) = √(P² + Q²)
Connected kVA = Base kVA × Quantity
Maximum Demand kVA = Connected kVA × Demand Factor ÷ Diversity Factor
Design kVA = Maximum Demand kVA × (1 + Safety Margin ÷ 100)
These formulas help estimate source loading for temporary panels, site feeders, transformers, and generator selection on construction projects.
How to Use This Calculator
- Enter a load name for your equipment or circuit.
- Select the calculation method that matches your available data.
- Choose single-phase or three-phase operation.
- Fill in voltage and either current, kW with power factor, or kW with kVAR.
- Add quantity, demand factor, diversity factor, and safety margin.
- Optionally enter hours and days for estimated monthly energy.
- Press the calculate button to show results above the form.
- Use the CSV or PDF buttons to export the output.
Frequently Asked Questions
1) What is apparent power?
Apparent power is the total electrical demand seen by a source. It combines real working power and reactive power. It is expressed in VA or kVA.
2) Why does phase type matter?
Single-phase uses S = V × I. Three-phase uses S = √3 × V × I. Three-phase systems deliver more power at the same line current.
3) Is kVA the same as kW?
No. kW is real power that performs work. kVA is apparent power the source must supply. They match only when power factor equals 1.0.
4) Why use demand and diversity factors?
Demand factor reduces connected load to expected simultaneous use. Diversity factor prevents overestimating shared equipment peaks. Together they produce more practical site estimates.
5) Should I include a safety margin?
Yes, when expansion, starting surges, or uncertain use patterns exist. A margin helps avoid undersized temporary power systems on busy projects.
6) Can this help with generator sizing?
Yes. It supports generator sizing, feeder planning, transformer checks, and temporary panel loading. Final decisions should still follow equipment data and local codes.
7) What does the graph show?
The graph shows how connected load becomes demand load, then design load, and finally a recommended generator size for planning.
8) Why is power factor important?
Power factor changes the relationship between kW and kVA. Lower power factor increases apparent power, current, and source size requirements.