Generator Sizing Calculator
Estimate the standby kW your facility needs from a simple load profile. The calculator factors HVAC tonnage, motor running and starting demand, and rounds the result up to a standard 25 kW band.
- Running load
- 61.5kW
- Worst-case starting
- 142.0kW
- Suggested genset
- 225kW
Calculation breakdown
- HVAC: 10 tons × 1.2 kW/ton = 12.0 kW
- Motor running: 15 HP × 0.746 × 0.85 = 9.5 kW
- Motor starting: 15 HP × 6 = 90.0 kW peak
- Min genset (running ÷ 0.8 or starting ÷ 0.65, whichever is greater): 218.5 kW
- Rounded up to standard 25 kW band: 225 kW
This is a starting-point estimate, not a substitute for a proper load study. Real applications need a non-coincident maximum analysis, load-step ordering for motor sequencing, harmonic loading from VFDs, and ambient/altitude derating. Confirm with the project's electrical engineer and the genset OEM's sizing tool (e.g., Cat Diesel SpecSizer, Cummins GenSize, Kohler PowerSize).
Need a real load study?
Our application engineers run formal load studies, motor-starting simulations, and OEM-sizing-tool reports for mission-critical installations.