What to do if the lights go out: home safety.(Home Front)(Column)

Homeowners can make blackouts more bearable by connecting a portable gasoline-powered generator into their home's wiring system. Models from Coleman, Generac, Honda, and other makers that supply the 5,000 watts or so needed for heating systems and other essentials cost $600 or more. Fuel use at 50-percent load is roughly one-half gallon of gas per hour.

To estimate your energy needs, decide which household systems and appliances you want to power simultaneously. Then follow these steps:

* Total the running wattage of what you'll power. Use the wattages on appliance nameplates or those below. For example, a gas furnace/blower, five 100-watt lights, a refrigerator, and a well pump would total 2,750 running watts.

* Separately total the starting, or surge, wattage to account for refrigerators and other devices with a motor, which temporarily draw more watts when they start. In this case, the maximum starting/surge requirement is 6,200 watts.

* Then choose a generator that supplies at least 2,750 running watts and 6,200 surge watts. Models with too little output won't be able to power the devices you want at the same time.

You'll need a transfer switch--safer than snaking multiple extension cords to the generator outside. A transfer switch is essential for furnaces and other devices that can't be unplugged. It also reduces the chance of an overload by letting you turn circuits on one by one. Two we tested that are suitable for 5,000-watt generators are the Square D Generator Panel Q04-8M30DS-GP, $140, and GenTran Manual Transfer Switch 20216, $250. Add about $300 for professional installation, more if extensive rewiring is needed.

Power on the cheap. AC power inverters, which connect to a car's battery, are an inexpensive alternative for briefly powering lights and a small appliance or two. Models that produce up to 300 watts typically cost less than $100. You won't have to run the car's engine for small, short-duration loads. You will for continuous loads or those beyond a few hundred watts.