Generator Sizing Calculator
AS/NZS 3010:2014 — Backup Power Design
Inputs
Above sea level
Peak expected temperature
Duty cycle classification
Results
Required Generator Rating
116
kVA
Selected Generator Size
Generator Sizing Guide — AS/NZS 3010:2014
Proper generator sizing ensures sufficient power for all loads during mains failure while accounting for motor inrush currents, starting methods, altitude and temperature derating, and application duty cycle. This calculator determines the required generator kVA rating with environmental and duty derating factors applied.
Load Categories
- Resistive Loads: Lighting, heaters. No inrush. 1× power factor.
- Motor Loads: Pumps, compressors, fans. Inrush on start. Multiplier >1× rated power.
- Reactive Loads: Transformers, magnetic ballasts. Low power factor. Higher VA than kW.
Derating Factors
- Altitude: Generators lose 3–4% capacity per 300 m above sea level due to reduced air density.
- Ambient Temperature: Above 25°C, generators derate. Most peak at 27°C, then lose ~1% per °C.
- Duty Cycle: Continuous vs standby use. Continuous duty is more conservative.
- Fuel Type: Diesel engines can handle continuous heavy loads; petrol generators are typically standby-only.
Application Class
- Standby (Emergency): Backup for mains failure. 500–3000 h/year. Reserve capacity acceptable.
- Prime Power: Primary source. 1500–8000 h/year. Moderate load variability.
- Continuous (Baseload): 24/7 power. >8000 h/year. No load variation tolerance. Highest capacity required.
Disclaimer: These results are indicative only. Generator selection must be designed and verified by a qualified electrical engineer in accordance with AS/NZS 3010:2014 and equipment manufacturer specifications before installation. Load duty analysis, fuel consumption, and maintenance schedules must be carefully planned.