Generator Sizing Guide
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GENERATOR SIZING GUIDE |
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Generators are rated in KVA. The following table shows how to express common loads in terms of generator KVA required. |
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Load type |
Common rating |
Multiplier |
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Motors |
(a) 1 phase |
HP |
x 1.5 |
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kW |
x 2 |
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VA |
x 1 |
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(b) 3 phase |
HP |
x 1.4 |
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kW |
x 1.9 |
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Lights |
(a) Incandescent/halogen – lamp watts |
x 1 |
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(b) Fluorescent – lamp watts |
x 1.5 |
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(c) Discharge (mercury/sodium) – lamp watts |
x 1.75 |
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Heating |
Nameplate rating kilowatts |
x 1 |
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Welders |
Electrode current - amps |
x 38(VA) |
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Electronic equipment |
Nameplate rating - VA |
x 2 |
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MOTOR STARTING FACTORS |
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Load type |
Example |
Multiplier |
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Low inertia |
Electric drill / unloaded motor |
x 2 |
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Medium inertia |
Medium skilsaw / Compressor with unloading device |
x 3 |
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High inertia |
Large diameter saw / compressor with no unloading device / pump starting against high head pressure |
x 4 |
GENERATOR SELECTION GUIDE
- Determine largest 1 phase load from sizing guide.
- If it is a motor, multiply by the appropriate starting factor.
- Add KVA equivalent of all other loads which will run at the same time.
- Multiply by 3
- Determine largest 3 phase load as determined from sizing guide.
- If it is a motor, multiply by the appropriate starting factor.
- Add the remaining 3 phase loads which will be running at the same time.
- Add the results of (7) and (4) and select the next largest sized generator.
QUICK GENERATOR SELECTION GUIDE
| Appliance | Rated Watts | Rated KVA | Rated KVA |
| Air conditioner (evaporative) | 275-1000 | 0.34-1.25 | 1.36-5 |
| Air conditioner (reverse cycle) | 200-2500 | 0.25-3.13 | 1-12.5 |
| Clothes dryer | 2400 | 3 | 3 |
| Coffee percolator | 550 | 0.69 | 0.69 |
| Can opener | 100 | 0.13 | 0.52 |
| Deep freezer | 500 | 0.63 | 2.52 |
| Disposal unit | 650 | 0.81 | 3.24 |
| Dishwasher | 1000-3000 | 1.25-3.75 | 1.25-3.75 |
| Domestic water pumps | 275-1000 | 0.34-1.25 | 1.36-5 |
| Exhaust fan | 40 | 0.05 | 0.2 |
| Food processor | 500 | 0.63 | 2.52 |
| Floor polisher | 350 | 0.44 | 1.76 |
| Frypan | 1400 | 1.75 | 1.75 |
| Hair dryer | 1500 | 1.88 | 1.88 |
| Hotwater service | 2500-3000 | 3.13-3.75 | 3.13-3.75 |
| Iron | 800-1500 | 1-1.88 | 1-1.88 |
| Kettle or jug | 1600-3000 | 2-3.75 | 2-3.75 |
| Lights | 25-200 | 0.03-0.25 | 0.03-0.25 |
| Microwave | 1500 | 1.88 | 1.88 |
| Oven | 4000-8000 | 5-10 | 5-10 |
| Radio | 60 | 0.08 | 0.08 |
| Radiator | 1000-2500 | 1.25-3.13 | 1.15-3.13 |
| Refrigerator (home) | 300 | 0.38 | 1.52 |
| Sewing machine | 60 | 0.08 | 0.32 |
| Space heater | 2000 | 2-5 | 2.5 |
| Television | 75-200 | 0.09-0.25 | 0.09-0.25 |
| Toaster | 250-1250 | 0.3-1.56 | 0.3-1.56 |
| Washing machine | 500-3000 | 0.63-3.75 | 2.52-15 |
| Welder 140 amp | 5000 | 6.25 | 8 |
(appliances) |
(generator to operate appliances) |
(generator to start appliance) |
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