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Depending on their wattage output, generators will run anything from a small lamp to a number of large appliances. To determine the size generator you will need, total the wattage of the maximum number of items you will be running simultaneously.

For items with start up ratings higher than their run ratings, use the higher rating to determine your power requirements.

Inductive load appliances and tools such as refrigerators, washers, and power tools require additional wattage for starting the equipment. The initial load only lasts for a few seconds on startup but is very important when calculating your total wattage.

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 initial start less power is required for actual operation.

For example: running a 100 watt light bulb, a 200 watt slow cooker, a 1,200 watt refrigerator with a start up wattage of 2,900 watts and a 750 watt TV would require 3,950 watts.

Use the chart below to help determine the right generator for you.

AVERAGE WATTAGE REQUIREMENT GUIDE (AMPS X VOLTS = WATTS)
Household	Approximate Wattage Required For Starting	Approximage 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

Ohm's Law

Remember Ohm’s Law to calculate Watts, Amps or Volts:
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 you’ll need from your generator.