# 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.