Uncle Bobs Tips: Generator Guide

What's What With Wattages?

Get to know your power wattage needs vis-a-vis your electric generator.

Generators are available anywhere from 900 watts to 100 KW+. How much juice you'll need is the most important aspect when deciding on a generator model. Mismatched workload and power output can be catastrophic.

The first thing we must realize when gauging appropriate wattage and workload is that there are two separates figures we will be working with. One figure is the amount of juice needed to run the appliance consistently. The other is an initial startup charge (surge wattage), which is considerably higher than the run figure (sometimes reaching double the running wattage). For example, a small fan could take 300 watts to run but 500 to start. You need to do a little arithmetic to get things running smoothly. Because of the large intake during start up, you may need to turn off some appliances before plugging in others.

Another point to mention is that many appliances are rated in amps (amperes). Generators work with watts, however. So, again, math is required, but don't worry, not too much. Basically, you need to multiply the volts times the amps. For example, a laptop could have an output of 16.5V and 3.6A. This would require roughly 60 watts to run.

Additionally, adding more to the grand total is a good idea as different brands and makes of the same appliance can vary as much as 20%. Finally, you don't want to be running on full load and leave yourself with 0 breathing room. Adding another little bit is advised for this reason (especially since many models are designed to automatically shut off when they reach nearly full to preserve the engine and wiring.)

Now for a little translation (physics, arithmetic, foreign language, you're getting a full university education here!) When companies write max output level this does not mean you can run your gen. at this level the entire time and be ok. The maximum output level is for initial power ups and limited short-term usage. Your generator will not perform at this level for a long period of time.

It's important to bear in mind when making these calculations that a generator is not meant to restore you to full system power. Keep in mind that this is in the event of a power outage or natural disaster, and a little self-sacrifice may be necessary (sorry, but you may have to hold off on running the central air full blast if the family also wants hot showers).

This chart will give you the approximate needed wattages for many of the appliances you will be running off your electric generator. These are not exact figures, and calculations should be made accordingly.

Air conditioner:   Clothes iron 1400
Central 5000 Light bulb: written on bulb
Room 1000 Incandescent 100
Clock radio 10-200 Compact fluorescent 25
Coffeemaker 850-1750 Microwave oven 800-1500
Clothes washer 425 Personal computer:  
Clothes dryer (electric) 3400 CPU+Monitor 125
Dishwasher 1800 Laptop 25-150
Dehumidifier 1800 Stereo 250
Electric blanket 80 Refrigerator 725
ELectric range 4500 Sump pump 600
Fans: 75-300 Television (color):  
Ceiling 120 20" (LCD) 65
Windows 150 26" (LCD) 110
Furnace 750 36-42" (Plasma) 250
Whole House 500 50-60" (Plasma) 340
Freezer (standing) 600 Toaster 1100-1750
Hair dryer 800-1700 Toaster oven 1225
Heating:   VCR/DVD 25
Central, gas furnace 400 Vacuum cleaner 1225

Central, oil furnace

1500 Water heater (electric) 5000
Electric, portable 1125 Well pump 700

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