Genset Sizing

Tick off the loads, and it works out the running watts, starting surge, and a realistic generator size.

Power supply

Are you sizing for a single-phase or three-phase supply?

Switch to three-phase to add heavier gear like welders, compressors, 3-phase A/C or pumps.

Connected loads

Tick quantities for what needs to run at once. Starting (surge) watts matter more than running watts for motor loads.

Appliance	Running W	Start W	Qty
Kitchen
Fridge / freezercompressor start	150W	800W	0
Chest freezercompressor start	100W	600W	0
Microwave	1200W	1200W	0
Electric kettle	2200W	2200W	0
Toaster	1000W	1000W	0
Induction cooktop (1 zone)	1800W	1800W	0
Laundry
Washing machinemotor start	500W	1500W	0
Clothes dryer	2400W	2400W	0
Dishwasherpump/heater start	1200W	1800W	0
Climate
Split A/C — 2.5kWcompressor start	900W	2700W	0
Split A/C — 5–7kWcompressor start	1800W	5000W	0
Ducted A/C — 8kW+compressor start	2500W	7500W	0
Portable electric heater	2000W	2000W	0
Pedestal / ceiling fan	70W	100W	0
Water & pumps
Pool pump (1HP)motor start	750W	2200W	0
Bore / pressure pumpmotor start	1100W	3300W	0
Sump / drainage pumpmotor start	800W	2000W	0
Electric hot water system	3600W	3600W	0
Workshop & outdoor
Angle grinder (medium)motor start	2000W	2400W	0
Circular sawmotor start	1400W	1600W	0
MIG welder (small, single-phase)	3000W	4500W	0
Air compressormotor start	1500W	4500W	0
Garage door motormotor start	500W	1200W	0
Lighting & electronics
LED lighting circuit (whole house)	150W	150W	0
TV / entertainment unit	150W	150W	0
NBN / router / modem	40W	40W	0
Laptop / phone charging	65W	65W	0

Custom items

Anything not covered above — a spa pump, an EV charger, whatever's specific to the job.

Safety margin

Headroom added on top of calculated peak demand.

Margin20%

20% is a sensible default — covers voltage sag and derating for altitude/heat.

Readout

0 loads selected · single-phase supply

0.0 kVA

/ 0.0 kW continuous, with margin

Nearest common size: 2 kVA / 1.6 kW

Total running load0W

Peak (with largest start-up)0W

With 20% margin0W

Approx line current0.0A

Nearest standard outlet10A

Check against a genset you're considering

kVA vs kW: generators are rated in kVA (apparent power). Motor-heavy loads (A/C, pumps, welders) run around 0.8 power factor, so kW ≈ kVA × 0.8. This calc sizes on kVA so surge loads aren't underestimated. The sizes above are common consumer/prosumer classes with kW estimated the same way — check the datasheet for your specific model, since some inverter generators rate kW closer to their kVA figure.

Line current: estimated at 230V — a rough guide for matching plug/socket and lead size, not a substitute for proper cable sizing.

Standards: a portable genset run into a switchboard needs a changeover switch or interlock installed per AS/NZS 3000 — never back-feed through a power point. A permanently connected standby genset also falls under AS/NZS 3010.