Calculator Inputs
Formula Used
- Total Connected Load (kW) = Connected Load + Additional Planned Load
- Estimated Demand (kW) = Total Connected Load × Utilization Factor × Demand Factor
- Coincident Demand (kW) = Estimated Demand ÷ Diversity Factor
- Design Demand (kW) = Coincident Demand × (1 + Growth Margin) × (1 + Safety Margin)
- Source Power (kW) = Design Demand ÷ Efficiency
- Apparent Power (kVA) = Source Power ÷ Power Factor
- Single Phase Current (A) = Apparent Power × 1000 ÷ Voltage
- Three Phase Current (A) = Apparent Power × 1000 ÷ (√3 × Voltage)
- Average Demand (kW) = Design Demand × Load Factor
- Monthly Energy (kWh) = Average Demand × Operating Hours Per Day × 30
- Recommended Protective Rating (A) = Line Current × 1.25
Percent inputs are internally converted to decimal values during calculation.
How to Use This Calculator
- Enter the total presently connected electrical load in kilowatts.
- Add any planned expansion load expected in the same system.
- Set utilization and demand factors to represent realistic loading.
- Enter a diversity factor above 1 when peak loads are noncoincident.
- Provide the power factor, voltage, efficiency, and phase type.
- Use load factor and daily operating hours for energy estimation.
- Add future growth and safety margins to obtain a practical design value.
- Press the calculate button to see results above the form.
- Use the CSV or PDF buttons to export the current result set.
Example Data Table
| Scenario | Total Connected Load (kW) | Demand Factor (%) | Diversity Factor | Power Factor | Voltage (V) | Phase | Design Demand (kW) | Current (A) |
|---|---|---|---|---|---|---|---|---|
| Office Distribution Board | 135.00 | 80 | 1.20 | 0.92 | 415 | Three | 108.16 | 170.37 |
| Light Industrial Workshop | 270.00 | 85 | 1.35 | 0.88 | 415 | Three | 211.14 | 355.10 |
| Single Phase Utility Room | 54.00 | 75 | 1.10 | 0.95 | 230 | Single | 39.59 | 186.79 |
These values are sample engineering scenarios for demonstration and comparison.
Frequently Asked Questions
1. What does demand load mean in electrical design?
Demand load is the realistic maximum load expected from connected equipment after applying usage and coincidence adjustments. It helps size feeders, breakers, transformers, and service entrances more accurately than raw connected load alone.
2. Why is diversity factor usually greater than one?
A diversity factor above one reflects that not all loads peak together. Dividing estimated demand by this factor reduces the coincident system peak and gives a more realistic service requirement.
3. How is demand factor different from load factor?
Demand factor compares maximum expected demand with connected load. Load factor compares average demand with peak demand over time. One supports sizing, while the other helps estimate energy usage and operational smoothness.
4. Why does power factor affect current calculation?
Lower power factor increases apparent power for the same real power. Because current is based on apparent power, a poorer power factor raises line current and can require larger conductors and protective devices.
5. Should I include future growth in demand studies?
Yes. Growth margin helps prevent early overloads and costly retrofits. It is especially useful in facilities expecting new machinery, occupancy increases, or future circuit additions within the same distribution system.
6. What is the purpose of the safety margin?
Safety margin adds design conservatism beyond calculated operating need. Engineers use it to absorb uncertainty, environmental effects, or operational variation before choosing practical equipment ratings.
7. Can this calculator be used for both single and three phase systems?
Yes. Select the phase type that matches your installation. The current formula automatically changes between single phase and three phase relationships using the entered system voltage and apparent power.
8. Are the results enough for final code compliance decisions?
No. This tool supports preliminary engineering estimates. Final conductor sizes, breaker selection, demand methods, and compliance checks should always follow the governing electrical code, equipment data, and licensed engineering judgment.