Generator and inverter sizing: 120% / 150%, kW not kVA
Source-Date (SAST): 2026-03-24 10:12
Dest: both
Review-after: 2027-08-31
Status: current
Facts
No big motor (no vacuum/dust/spindle-class motor): size = machine kW × 120%. With a big motor: × 150%. Multiple machines: add the results. Always round up to the next marketed size, never down.
Example: LM-RUSTOFF/2000 5.2 kW → 6240 W → a 7 kW 220 V generator. LM-RUSTOFF/3000 6.7 kW → 8040 W → a 9 kW 380 V generator. Do not buy an 8 kW unit that claims 9 kW burst.
Most generators are marked kVA, not kW. Typical power factor 0.8 so 9 kW ≈ 11.25 kVA. Advise the client to check real output kW. Power factor below 0.8 is a poor generator. 380 V generators can feed 220 V; 220 V cannot feed 380 V.
Add accessories (e.g. a compressor) with the same ratio. Inverters/solar use the same kW maths; they are usually marked in kW. Ignore burst ratings.
