Generator Power Calculator
Calculate electrical power requirements for generators with AC and DC supply types
Calculate Generator Power Requirements
Single phase AC: 2 wires (live + neutral), domestic use
Sum of current ratings of all connected devices
Voltage rating from device specifications
Ratio of real to apparent power (typically 0.8 for generators)
Motor efficiency for horsepower calculation (typical: 80-95%)
Example Calculation
Home Backup Generator
Supply type: AC Single Phase
Total current: 50 A (sum of all appliances)
Supply voltage: 240 V
Power factor: 0.8
Motor efficiency: 85%
Results
Apparent power: S = 240V × 50A = 12.0 kVA
Real power: P = 240V × 50A × 0.8 = 9.6 kW
Motor horsepower: HP = (9.6 × 0.85) / 0.746 = 10.9 HP
Recommendation: 12-15 kW generator with 20% safety margin
Power Supply Types
Single Phase AC
Domestic applications
2 wires: live + neutral
Three Phase AC
Industrial motors
3 live wires + neutral
Direct Current
Battery systems
Steady voltage level
Generator Sizing Guide
Portable (1-5 kW)
Camping, small tools, emergency lighting
Home Backup (5-20 kW)
Essential appliances, partial home power
Whole House (20-50 kW)
All appliances, HVAC systems
Commercial (50+ kW)
Industrial equipment, large facilities
Understanding Generator Power Calculations
How Generators Work
An electrical generator converts chemical energy (fuel) into electrical power through multiple stages: chemical → thermal → mechanical → electrical energy. The mechanical energy rotates coils in a magnetic field, generating electrical current through electromagnetic induction.
Power Types
Apparent Power (kVA) is the product of voltage and current without considering phase relationships. Real Power (kW) is the actual usable power, calculated using the power factor which accounts for the phase difference between voltage and current in AC circuits.
Applications
- •Emergency power for homes and offices
- •Construction sites and remote locations
- •Hospital and critical facility backup
- •Outdoor events and recreational activities
Key Formulas
Single Phase AC
Apparent Power: S = V × I (kVA)
Real Power: P = V × I × PF (kW)
Three Phase AC
Apparent Power: S = √3 × V × I (kVA)
Real Power: P = √3 × V × I × PF (kW)
Direct Current
Power: P = V × I (kW)
No apparent power or power factor
Motor Horsepower
HP = (P × η) / 0.746
where η is efficiency (0-1)
Sizing Tip: Always add 20-25% safety margin to calculated power requirements when selecting a generator to account for starting currents and future load additions.