Zendine Generators
470 NORTH BRIDGE ROAD #02-09 SINGAPORE 188735    TEL:+65 65840112    FAX:+65 67660579

Associate Reps Offices in China, Indonesia, Taiwan, Malaysia & Canada
 
 
FAQ's: What Size Generator Do I Require?

Generator Sizing Guide

Power requirements must be determined to properly size your generator. We are providing some steps to assist you in approximating the size generator for your power needs. Please keep in mind that unless you are qualified, you should use a certified electrician to determine your power needs. At Americas Generators it is our goal to assist our customers in any way possible. If you have any questions, please do not hesitate to contact us.

STEPS TO DETERMINE GENERATOR REQUIREMENTS

  1. Determine your need. Do you want the generator to operate part or all of your home or office?
  2. Identify the appliances and/or tools the generator will need to power.
  3. Determine the wattage for each appliance and tool you plan to use frequently. The "Common Wattage Guide" below will help you determine your need.
  4. Total the wattage for appliances and tools you frequently use.
  5. Identify motor and pump requirements. Use the motor and pump charts provided below.
  6. Calculate and total the wattage for the motors and pumps frequently used. Always use starting watts, not running watts, when determining the correct electrical load requirements.
  7. Total the wattage of the appliances & tools and the motors & pumps. Keep in mind that if you coordinate your power usage wisely you do not have to operate everything all at once. Therefore, for emergency use you don’t necessarily need to size the generator to operate everything simultaneously.
  8. Convert watts into kilowatts by dividing the watts in step VI. to determine the generator size required. Please note that it is suggested, although not absolutely necessary, to size the generator 20-25% over the size you determine your needs to be. This will allow room for future growth. For example, if you determine that you will need a 15 kW generator then it is advisable to purchase an 18 kW generator to accommodate future expansion.

 COMMON WATTAGES

Item Running Watts Starting Surge
100 watt light bulb 100 100
Radio AM/ FM stereo 50-200 50-200
Radio CB 50 50
Fan 200 200
Television 300-400 300-400
Microwave oven 700 1000
Air conditioner 3250 5000
Furnace fan (1/3 HP blower) 600 1800
Vacuum cleaner 600 750
Sump pump (1/3 HP) 700 2100
Refrigerator/ Freezer 800 2400
Freezer 500 1500
6" circular saw 800 1000
Floodlight 1000 1000
1/2" electric drill 1000 1250
Toaster 1200 1200
Coffee maker 1200 1200
Electric skillet 1200 1200
14" electric chain saw 1200 1500
1/2 HP water well pump 1000 3000
Hot plate 1500 1500
Electric range 10000 10000
10" table saw 2000 6000
Hot water heater 5000 5000

ELECTRIC MOTOR WATTAGE REQUIREMENTS

Electrical motors present special electrical startup considerations. They can require up to three times their rated running wattage to start. Motor nameplates generally will show starting watts, some as high as nine times the running wattage. Check the nameplate to be sure. Be certain to use the starting watts when figuring the correct electrical load requirements. Motor load requirements are listed below:

Motor Rating HP

Approximate Running Watts

Universal Motors Small Appliance

Reduction Induction Motors

Capacitor Motors

1/8

275

400

600

850

1/4

400

500

850

1050

1/3

450

600

975

1350

1/2

600

750

1300

1800

3/4

850

1000

1900

2600

1

1000

1250

2300

3000

1 1/2

1600

1750

3200

4200

2

2000

2350

3900

5100

3

3000

3550

5200

6800

** Motors of higher HP are not generally used.

WATER WELL PUMP KW REQUIREMENTS

Pump HP Rating

Externally Regulated Generator

Internally Regulated Generator

 

Min. KW

Min. KVA

Min. KW

Min. KVA

1/3

1.5

1.9

1.2

1.5

1/2

2.0

2.5

1.5

1.9

3/4

3.0

3.8

2.0

2.5

1

4.0

5.0

2.5

3.125

1 1/2

5.0

6.25

3.0

3.8

2

7.5

9.4

4.0

5.0

3

10.0

12.5

5.0

6.25

5

15.0

18.75

7.5

9.4

7 1/2

20.0

25.0

10.5

12.5

10

30.0

37.5

15.0

18.8

  NOTES: 1. It is recommended that the generator be started before the pump motor is turned on.

  • A majority of industrial generators are externally regulated. Generators must be sized to deliver at least 65% of the rated voltage during motor starting to ensure adequate motor starting torque.
  • Industrial generators typically produce 300+ percent of rated capacity for 15-20 seconds during electrical surges.
  • To convert KW into watts multiply KW (x) 1000.