Generator Expert

Which Generator Do I Need?

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Buying the right generator can seem like a formidable task, but in just a few easy steps, you can effectively decide which generator is right for the customer.

  1. Identify the tools and appliances the customer wishes to operate with the generator
  2. Determine the required power for each item
  3. Total the required watts of the items that will be run simultaneously (allowing for motor starting)
  4. Choose the generator that has rated watts that meet or exceed this total power

Use the following formulas to calculate the power required:

Power conversions:

1 kw = 1.25 kva
1 kva = 0.80 kw
1 kw = 1000 watts
1 kw = 1.34 hp amps x volts = watts

To convert:

kva to kw multiply by 0.8
kw to kva divide by 0.8
watts to kw divide by 1000

Motor starting is an important factor when buying a generator. keep in mind that induction-type motors (i.e. sump pumps, refrigerators and compressors) typically require 2 to 3 times their listed running watts to start.

Below is a list of tools and appliances customers may wish to use:

appliance app. running watts appliance app. running watts appliance app. running watts appliance app. running watts
light bulb 100 palm sander 175 slow cooker 200 radio/hi-fi 200
colour tv 250 vdu 300 strimmer 10” 350 printer 350
jig saw 400 bench grinder 400 computer 400 13 mm drill 450
orbital sander 450 hedge trimmer 500 flood lamp 500 4” angle grinder 550
1/3 hp sprayer 600 facsimile 600 deep freeze* 700 fridge* 700
planer 700 5" angle grinder 750 hairdryer 1000 lawnmower 1000
5" circular saw 1000 router 1000 belt sander 1020 vacuum cleaner 1100
coffee maker 1200 cement mixer* 1320 chain saw 10-16" 1500 600w microwave 1500
portable heater 1500 hot air gun 1500 photocopier 1600 8" floor sander 2000
compressor* 2200 12" grinder 2500 hammer drill 2500 kettle 2500
fan heater 3000 hammer/breaker 3000 1 hp pre. washer 3500 washing machine 4000

* see motor starting

Below is a chart you can use to determine how many watts you will need to start up motors of various sizes and types.

motor size hp running watts starting watts required
1/8 275 850
1/6 275 850
1/4 400 1050
1/3 450 1350
1/2 600 1800
3/4 850 2600
1 1100 3300
2 2200 6600