Portable Generators - What to Look For
 

Most portable generators now use fuel-efficient four-cycle OHV (overhead valve) engines that are easier to start, quieter and are better for the environment than two-cycle engines. (You can tell it's a two-cycle engine if you have to mix oil into the gasoline.) The four-cycle OHV engines last longer, too. Most new portable generators also provide circuit breakers, use electronic governors to regulate voltage and provide some weather protection for outlets and controls.

In choosing a portable generator, consider the following:

  • Never use a generator indoors. Because generators exhaust far more carbon monoxide than an idling car, it is extremely dangerous (and in some cases lethal) to run them indoors or even in a crawl space or garage.
     

  • Consider the "rated wattage" with care. Wattage ratings are tested under ideal conditions; lower temperatures and/or higher elevations will lower the amount of electricity produced. Use the "rated wattage" rather than the "maximum" or "surge" wattage in calculating what a portable generator will produce. Experts recommend allowing about a 20-percent margin.
     

  • CARB compliance means lower emissions. Portable generator engines that meet California's Air Resources Board requirements, sometimes called "50-state compliant" models, are the most environmentally friendly. Budget portable generators may be only "49-state compliant," meaning they can't be sold in California because they pollute the air more.
     

  • Acceptable sound levels depend on the situation. Portable generators can be as quiet as 47 decibels or as loud as 79 -- with the average about 75 decibels, about like the newest leaf blowers. For camping, note that The National Park Service requires sound levels no higher than 60 decibels at a distance of 50 feet.
     

  • Full lubrication with a spin-on oil filter prolongs engine life while reducing maintenance. For example, you may need to change the oil every 100 hours instead of every 24. Reviews say portable generator engines with this feature cost more, but last up to three times longer.
     

  • Automatic low-oil shutdown can save the generator. Portable generators with this feature shut themselves down if the oil gets too low, so the motor isn't ruined. Less expensive models without this feature require vigilant attention.
     

  • A fuel gauge adds convenience. When reviewing less expensive portable generators, this is one of the features owners miss most. The fuel gauge also reminds you to check the oil, since that should be done every time you add fuel.
     

  • Idle control can save fuel by adjusting the engine according to smaller loads -- at one-fourth, half or three-fourths of the rated wattage. However, this also limits the wattage available for starting big motors, so you may not be able to use this feature all the time, even on the top-rated Honda and Yamaha models that use automatic "smart throttles."
     

  • A USDA or US Forest Service approved spark arrester is especially important for portable generators used for camping, and to help prevent fires in household locations, as well.
     

  • For household use, look for at least four outlets: preferably lock-on, with GFCI, plus one DC outlet. Locking outlets are safest, since a cord that pulls a bit loose from the generator can cause a fire. Safety experts recommend OSHA-approved ground-fault-circuit-interrupter (GFCI) outlets, since portable generators are often used in wet conditions (and they may be required at certain jobsites). If you have one 12-volt DC outlet, you can even use the generator to recharge your car's battery.

When purchasing a portable generator, you should match the unit's electrical generating capacity to the power requirements of your most-needed appliances. Certain appliances demand higher start-up or surge wattages. A refrigerator, for example, runs on about 850 watts, but momentarily can require twice as much power at start-up. To calculate your power needs, simply add up the constant and surge wattage figures for all the devices you want to operate simultaneously and round it up to allow for a little buffer.

The minimum recommended generator for powering residential buildings is a 5,000-watt (5-kW) unit. A generator of this size typically costs between $600 and $1,200 and can power multiple appliances for about 8 hours on one tank of fuel. Many can produce either 120 volts or 240 volts of household (alternating current) power. Be sure to check its power rating at the voltage you will be using.

To enable the generator's power to run to your home's outlets and ceiling lights or to powered appliances such as ranges, ovens, furnaces and well pumps, a licensed electrician should install a transfer switch that distributes power from the generator to the home's circuit-breaker panel. Transfer switches are safe, efficient, permanent devices that also eliminate the risk of electrical "backfeed" to, or from, the utility power grid (when electricity comes back on).

Smaller portable generators may be connected directly to appliances by appropriately sized copper extension cords. However, use caution: Undersized cords could damage the generator and appliances and create a fire hazard.

Consider staggering power use among your major appliances so you don't encroach on the generator's capacity. For example, run the refrigerator for an hour, and then shut it off and power up the air conditioner for an hour. By doing this, you'll conserve fuel and prolong the life of your generator.

Finally, keep in mind that gas station pumps won't operate during a blackout, so stock enough fuel to run your generator for several hours -- and store the fuel in a safe place outside, not inside, your home