Choosing a Backup Generator

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If your home is grid-connected, you don't need to spend a lot of money on a backup generator to weather the occasional power outage because typically, backup generators are used less than 50 hours a year. Large standby generators can cost several thousand dollars, but smaller portable models will power basic necessities and cost $1,000 or less, some as little as $400. Even a less expensive generator will run at least 500 hours, giving you about 10 years of service. But if you plan to install solar or wind power, or you live in a rural area on a distribution line that suffers frequent power outages, you will need a larger capacity generator. Those that back up renewable energy systems operate between 100 and 200 hours a year. The load is heavier because they run your household and recharge your renewable energy system's batteries at the same time.

Regardless of what size generator you need, it is important to shop around and do your research—prices vary greatly from brand to brand and, according to Consumer Reports, some models deliver less power than they promise. Best-buy-rated models were the Generac 5500 WheelHouse and the Troy-Bilt 5550 (each $650; www.consumerreports.org ).

SIZING YOUR GENERATOR

It's important to match the size of your generator to your electrical needs. An undersized generator won't last long and can destroy motors and other electrical equipment that require more current than the generator can deliver. Generators are rated by their maximum electrical power output in kilowatts. (A kilowatt equals 1,000 watts, or enough energy to light 10 100-watt light bulbs.) For greatest efficiency and to prolong your generator's life, operate it at no more than 75 percent of its capacity.

To calculate the generator size you need, total the wattage of the appliances and other items you want to simultaneously power and then double that number. If you plan to power several appliances, you need to account for their starting or "surge" requirements. You can find this information on the appliance or in its manual.

Most homeowners will need a 5-kilowatt portable generator to power a heating system and a few other essentials (a furnace uses from about 1,800 watts to 3,500 watts, depending on the type of furnace and the size of the house). A generator of this size will cost at least $600 and, when running at 50-percent load, wlll consume about half a gallon of gasoline per hour. Larger portable generators use more fuel and cost up to $3,000. Permanent standby generators with automatic operation generally cost between $2,200 and $10,000.

Controlled Power Company of White River Junction, Vermont, sells permanent standby generators for residential use in northern New England. According to Timothy Tobin, the company's president, the demand for larger units is growing. "Fifteen years ago, the standard home generator was in the 5-kilowatt range, but today the most popular size is 12 kilowatts, and we've actually sold some up to 70 kilowatts."

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