What generator power do you need
This is an estimate. A manager will confirm the exact power, especially if you have many motors or welding equipment.
Find the power in kW on the equipment nameplate. If it shows amperes, switch to calculation by current.
| Equipment | kW | Qty | Start type | Remove |
|---|
The incoming circuit breaker rating is printed on the breaker itself, e.g., "C100" means 100 A. The result is the power the incoming supply is rated for.
Why we calculate this way
20% margin over the load
A generator that constantly runs at its limit wears faster, runs hotter and holds voltage worse under load surges. The margin keeps the engine in a comfortable operating mode so it lasts longer, and lets you connect new equipment without replacing the generator.
Direct-on-line start: ×3
A pump, compressor or refrigeration unit started direct-on-line draws several times its running current in the first seconds. If the generator cannot handle this, the motor will not start: the protection will trip or the voltage will sag for the rest of the equipment. That is why we count the start of the largest such motor at triple its power on top of the remaining load.
VFD or soft starter: ×1.5
A variable frequency drive or soft starter accelerates the motor gradually, so the starting current is much lower. Such equipment needs only a 1.5× starting margin. If your pumps have VFDs, specify this: the generator may turn out noticeably smaller and cheaper.