# Generator Wattage Guide

Wattage Calculator
RenTrain Editors

There are different categories to consider when choosing a generator for your needs: recreation, home standby and construction. You may also want to consider using an inverter generator for sensitive electronic devices. Inverter generators are smaller and lighter as power is created electronically and not through a conventional alternator. Inverter power offers the cleanest power output.

If you want a generator for home standby, say to run your refrigerator, you'll 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, you'll want a generator with at least 3000 watts.

You'll 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 Ohm's Law
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.

### AVERAGE WATTAGE REQUIREMENT GUIDE(AMPS X VOLTS = WATTS)

Household
Running
Wattage
Requirements
Wattage Required
For Starting

Coffee Maker

1750
0
Dishwasher
Cool Dry
700
1400
Electric Fry Pan 1300
0
Electric Range
8-inch element
2100
0
Microwave Oven 625 watts
625
800
Refrigerator or Freezer
700
2200
Automatic Washer
1150
2300
Clothes Dryer
Electric
5750
1800
Furnace Fan, gas or fuel oil
1/8 Horsepower 300
500
1/6 Horsepower 500
750
1/4 Horsepower 600
1000
1/3 Horsepower 700
1400
1/2 Horsepower 875
2350
Lights as indicated on bulb
0
50 to 200 0
Sump Pump
1/3 Horsepower 800
1300
1/2 Horsepower 1050
2150
Television - Color 300
0
Central Air Conditioner
10,000 BTU
1500
2200
Contractor
Running
Wattage
Requirements
Wattage Required
For Starting
Air Compressor
1 Horsepower
1500
4500
Bench Grinder
8 inches
1400
2500
Hand Drill
1/2 inch
600
0
High-pressure Washer
1 Horsepower
1200
3600
Circular Saw, Heavy Duty
71/4 inches
1400
2300
Electric Chain Saw
14 inches, 2 Horsepower
1100
0
Table Saw
10 inches
1800
4500
Drills
3/8 inch 4 amps 440
600
1/2 inch 5.4 amps 600
900
Industrial Motors
Running
Wattage
Requirements
Wattage Required
For Starting
Split Phase
1/4 Horsepower 600
1000
1/2 Horsepower 875
2300
Capacitor Start Induction Run
1/3 Horsepower 720
1300
1 Horsepower 1600
4500
Capacitor Start Capacitor Run
11/2 Horsepower 2000
6100
Fan Duty
1/4 Horsepower 650
1200
Farm Equipment
Running
Wattage
Requirements
Wattage Required
For Starting
Electric Fence, 25 miles 250
0
Milk Cooler 1100
1800
Milker (vacuum pump),
2 Horsepower
1000
2300
Portable Heater (kerosene, diesel fuel)
50,000 BTU 400
600
90,000 BTU 500
725
150,000 BTU 625
1000
Battery Charger
15 amp 380 0
60 amp with 250-amp boost
1500/5750 0
100 amp with 300-amp boost
2400/7800
0
Electric Welder
200 amp AC 9000 0
230 amp AC, at 100 amp 7800 0
Air Compressors Running
Wattage
Requirements
Wattage Required
For Starting
1/2 Horsepower 975 1600
1 Horsepower 1600 4500

Computers
Running
Wattage
Requirements