Question 1

What is the difference between kW and kVA on a generator?

Accepted Answer

kW (kilowatts) is the real power — the actual work the generator does. kVA (kilovolt-amperes) is the apparent power — the total electrical load including reactive power from motors and transformers. Most generators are rated in kVA. To convert kVA to kW, multiply by the power factor (typically 0.8 for farm generators). A 10 kVA generator produces approximately 8 kW of usable power. Always check the kW rating, not just the kVA, when sizing a generator for a specific load.

Question 2

What are surge watts and why do they matter?

Accepted Answer

Electric motors — compressors, water pumps, angle grinders, augers — draw 2 to 3 times their running wattage for a fraction of a second when they start up. This is called the surge or starting load. If your generator cannot supply this surge, it will either fail to start the motor, stall under load, or trip its overload protection. Always size your generator based on the highest surge load you will encounter, not just the running load. The calculator above accounts for this automatically.

Question 3

Should I buy a diesel or petrol generator for farm use?

Accepted Answer

For occasional use (less than 100 hours per year), a petrol generator is cheaper to buy and adequate for the task. For regular farm use — powering milking equipment, grain handling, regular workshop use — a diesel generator is significantly more economical to run (approximately 30% less fuel per kWh), more durable, and easier to source fuel for on a working farm. Diesel generators are also safer to store fuel for on farm premises.

Question 4

Can I run a welder from a generator?

Accepted Answer

Yes, but check both the generator output and the welder's input requirement carefully. A MIG welder at 140 amps typically requires around 4 kW of input power at 240V. You need a generator with at least 5–6 kVA to run it reliably, accounting for power factor and headroom. Inverter generators produce cleaner power that is better for sensitive electronics, but a standard generator is fine for most welders. Always check the welder's manual for minimum power supply requirements.

Question 5

What size generator do I need for a farm water pump?

Accepted Answer

A typical farm water pump of 1.5 kW running power needs a generator that can handle a startup surge of up to 4.5 kW (3× running load). Allow for a surge factor of 3 on all centrifugal pumps. A 5 kVA generator (4 kW) will start and run a 1.5 kW pump comfortably. For a 2.2 kW pump, you need at least a 7–8 kVA generator. Use the calculator above to check your specific pump requirements.

Question 6

How much fuel will my generator use?

Accepted Answer

Fuel consumption depends on load — generators use significantly less fuel at partial load. At 75% load, a typical diesel generator uses approximately 0.21 litres per kVA per hour. A 10 kVA diesel generator running at 75% load uses around 2.1 litres per hour. A petrol generator of the same size uses approximately 3 litres per hour. The calculator estimates fuel consumption based on your recommended generator size and fuel type.

Question 7

Can I run three-phase equipment from a single-phase generator?

Accepted Answer

Not directly. Single-phase generators cannot run three-phase motors without additional equipment. Options include using a three-phase generator (more expensive), a phase converter (adds complexity and reduces motor efficiency), or — for farm use — replacing the three-phase motor with a single-phase equivalent where possible. If you have three-phase equipment such as a grain dryer fan or large milk vacuum pump, specify a three-phase generator from the outset.

Question 8

How much headroom should I allow when sizing a generator?

Accepted Answer

Always allow at least 20% headroom above your calculated peak load. Running a generator at or near its maximum rating continuously shortens its life, increases fuel consumption and reduces voltage stability. For farm use where you may add equipment over time, allowing 25–30% headroom is sensible. The calculator applies a 20% headroom factor automatically in its recommendation.

Equipment	Running Watts	Surge Factor	Peak Surge
Air compressor (2.2 kW)	2200 W	×3	6600 W
Water pump (1.5 kW)	1500 W	×3	4500 W
MIG welder (140A)	4000 W	×1.2	4800 W
Angle grinder (large)	2300 W	×2	4600 W
Milk vacuum pump (2.2 kW)	2200 W	×2.5	5500 W
Milk bulk tank cooler	3000 W	×2.5	7500 W
Feed auger (1.5 kW)	1500 W	×2.5	3750 W
Pressure washer (2.5 kW)	2500 W	×2	5000 W
LED floodlight (200W)	200 W	×1	200 W
Electric fan heater (3kW)	3000 W	×1.5	4500 W

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