What You Need to Know When Buying a Generator

Tired of blackouts? Buy an emergency generator

A good size for emergency backup is 5,500 watts

If you’re shopping for a portable generator—that is, one on wheels that’s not permanently connected to your home’s electrical system—a generator that supplies 5,500 watts is about the right size. This is enough to power a few critical appliances like a refrigerator, furnace, microwave, TV and some lights. Of course, you can’t run a whole-house air conditioner and an electric water heater at the same time with 5,500 watts, but a generator this size will get you by until the power comes back on. You can buy a good-quality 5,500-watt generator for about $700.

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Buy a standby generator if you can afford it

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Propane is easier than gas

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Buy a generator you can get serviced locally

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Furnaces, well pumps and electric water heaters require a transfer switch

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Add up your watts—then add extra for motor start-up

If you’re the adventurous type, you can just go with our recommendation of a 5,500-watt generator and make the best of it. But if you really want to know what size generator you need to power everything you want, then the only way is to add up the wattage of all the lights, appliances and motors that you intend to run simultaneously.

Generator manufacturers and resellers have charts you can refer to that list the average wattage used for various appliances and motors. Or you can check the nameplates on the appliances you want to power. If wattage isn’t listed, you can derive it by multiplying volts by amps. For example, if the plate lists 2.5 amps at 120 volts, multiply the two to get 300 watts.

There’s one caveat, though. Motors require an extra surge of electricity to get started, and you have to factor this into the equation. Add up the wattage of everything you want to run. Then determine the largest motor you need to run (the furnace, for example), multiply the wattage requirement by 2 to get the approximate startup wattage required, and add this number to the total.

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Buy gas cans when you buy the generator

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You'll need heavy-duty extension cords

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Don't wreck your TV with a cheap generator

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You can buy a quiet generator, but it'll cost more

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