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You are here: Home > Do it yourself > GENERATOR WATTAGE CALCULATOR

GENERATOR WATTAGE CALCULATOR


Depending on how you will use your generator, there are different categories to meet your needs. This can include recreation, home standby and construction. Honda also offers Inverter Generators. Inverter generators are smaller and lighter as power is created electronically and not through a conventional alternator. Inverter power offers the cleanest power output, ideal for sensitive electronic devices.

If you want a generator for home standby, for example, if you want to run your refrigerator, youll need at least 2500 watts or more. And if you want to use a transfer switch so that power can go directly into your home, youll want a generator with at least 3000 watts.

Youll also need to consider the maximum and rated power of the generator. This is important depending on what items you want to run off of your generator. Items such as toaster, lamps, and coffee makers are resistive, or constant loads and their total load can be calculated at amps x 1. Items such as saws and drills are reactive loads and while the running load may be small, the starting load should be calculated at running amps x 3. Remember, after the intial start less power is required for actual operation.

Always remember that simple power management will allow a smaller generator to do a big job. Very seldom are all tools or appliances operating simultaneously. When calculating power requirements, consider the starting requirements are only for the initial start and then additional tools may be operated in addition.

Remember Ohms Law from High School Physics?
Watts = Volts x Amps
Amps = Watts/Volts

So if you have two of the numbers (e.g. volts, amps) then you can find out the other (e.g. watts). This can help you to determine the rated power that youll need from your generator.

AVERAGE WATTAGE REQUIREMENT GUIDE

(AMPS X VOLTS = WATTS)
Household
Approximate
Wattage Required
For Starting
Approximate
Running Wattage
Requirements

Coffee Maker

600
600
Dishwasher
Cool Dry
540
216
Electric Fry Pan 1500
1500
Electric Range
8-inch element
2100
2100
Microwave Oven 650 watts
1000
1000
Refrigerator or Freezer Energy Star
1200
132-192
Automatic Washer
1200
1200
Clothes Dryer
Electric
6750
5400
Furnace Fan, gas or fuel oil
1/8 Horsepower 500
300
1/6 Horsepower 750
500
1/4 Horsepower 1000
600
1/3 Horsepower 1400
700
1/2 Horsepower 2350
875
Incandescent Lights as indicated on bulb
as indicated on bulb
Radio
50 to 200 50 to 200
Sump Pump
1/3 Horsepower 1300
800
1/2 Horsepower 2150
1050
Television - Color 300
300
Air Conditioner
10,000 BTU
2200
1500
Contractor
Approximate
Wattage Required
For Starting
Approximage
Running Wattage
Requirements
Air Compressor
1 Horsepower
4500
1600
Bench Grinder
8 inches
2500
1400
Hand Drill
1/2 inch
900
600
High-pressure Washer
1 Horsepower
3600
1200
Circular Saw, Heavy Duty
71/4 inches
2300
1400
Electric Chain Saw
14 inches, 2 Horsepower
1100
1100
Table Saw
10 inches
4500
1800
Drills
3/8 inch 4 amps 600
440
1/2 inch 5.4 amps 900
600
Industrial Motors
Approximate
Wattage Required
For Starting
Approximage
Running Wattage
Requirements
Split Phase
1/4 Horsepower 1700
400
1/2 Horsepower 2600
600
Capacitor Start Induction Run
1/3 Horsepower 975
450
1 Horsepower 2300
1000
Capacitor Start Capacitor Run
1 1/2 Horsepower 4200
1600
Fan Duty
1/4 Horsepower 1200
650
Farm Equipment
Approximate
Wattage Required
For Starting
Approximage
Running Wattage
Requirements
Electric Fence, 25 miles 250
250
Milk Cooler 1800
1100
Milker (vacuum pump),
2 Horsepower
2300
1000
Portable Heater (kerosene, diesel fuel)
50,000 BTU 600
400
90,000 BTU 725
500
150,000 BTU 1000
625
Battery Charger
15 amp 380 380
60 amp with 250-amp boost
1500/5750 1500/5750
100 amp with 300-amp boost
2400/7800
2400/7800
Electric Welder
200 amp AC 9000 9000
230 amp AC, at 100 amp 7800 7800
Air Compressors Approximate
Wattage Required
For Starting
Approximage
Running Wattage
Requirements
1/2 Horsepower 1600 975
1 Horsepower 4500 1600

Computers
Approximate
Wattage Required
For Starting
Approximage
Running Wattage
Requirements
Desktop 600 to 800 600 to 800
Laptop 200 to 250 200 to 250
Monitor (CRT) 200 to 250 200 to 250
Fax 600 to 800 600 to 800
Printer 400 to 600 400 to 600