Single-Phase 230 V Generators

Sizing starts from the combined real power of everything running at once, plus a 20–30% margin. A 1.1 kW drill, a 2.2 kW grinder and 0.3 kW of lighting come to about 3.6 kW, which in practice calls for a 5–6 kVA set at a power factor of 0.8. Rated current alone is not a sufficient guide: induction motors draw 3–7 times their working current on start-up, so a 2.2 kW machine can load the generator with 6–8 kW for a moment. Above 1,000 m altitude or in temperatures over 30°C, allow a few percent more for the loss of engine output.

Socket capacity is set by its own rated current, not by the output of the whole generator. A standard 16 A socket at 230 V carries about 3.7 kW continuously and a 32 A socket about 7.4 kW. That means a 6 kVA generator fitted with two 16 A outlets only gives its full output once the loads are split across both of them. An overloaded socket trips its protection before the set reaches rated power. Long cable runs add voltage drop — around 11 V over 50 m of 2.5 mm² cable at 16 A.

Starting any induction-motor machine calls for spare capacity to cover the inrush current. A 0.8–1.5 kW cement mixer normally starts from a 3–5 kVA set, whereas a 2–3 kW pump or electric compactor realistically needs a 5–7 kVA unit. Start machines one at a time, beginning with the one that draws the highest inrush current. If the voltage sags and the motor hums without spinning up, the generator is undersized or the supply cable is too thin.

Fuel consumption is driven mainly by load. Petrol generators in the 3–7 kVA class typically burn 1–2.5 l/h at around 75% of rated output, and as little as half that at idle. With a 15–25 l tank this works out at roughly 6 to 12 hours of continuous running — one or two shifts without refuelling. An engine held at the edge of its output burns more and runs hotter, so a 20–30% margin lowers the hourly cost. At light loads, inverter generators are the more economical option.