A small gas engine is visible inside the housing of this standby generator being installed at home.
Photo by Kohler
Question: I’m considering purchasing a backup generator for my home, so I’ll be prepared if severe weather hits. What would you recommend?
Answer: These days, most families depend on electricity for nearly every activity, so homes with backup generators are becoming more common.
Residential backup generators are called standby models, because they are used only when electricity from the utility grid fails. They are designed to run for a relatively short period of time, until power is restored—usually between a few hours and a couple of days.
First, to determine the size of the backup generator you’ll need, decide how much of your home you’d like to power. Common necessities, such as refrigeration and lighting, will definitely need power. Others, such as air conditioning, washing and drying clothes, and vacuuming, may not be top priority during a power outage.
Backup generators are sized by their kilowatt electricity output. A 12-kW generator can power most electrical needs for a typical family of four. If you eliminate nonessentials, a smaller, less expensive unit will be adequate, and the fuel costs to operate it will be less.
To get a rough idea of what size generator you will need, list all electric items you want to power, and total their wattages. Items and appliances with motors often require more electric current at start-up time, so round up when calculating the total wattage. Ask a contractor or installation expert to advise you on the proper size—installing a whole-house backup generator is not a do-it-yourself project.
For convenience and safety (for both your family and your electric cooperative’s emergency lineworkers), have an automatic transfer switch (ATS) installed. This switch senses when the grid electricity goes off or the voltage drops below a critical point. It automatically disconnects your home’s wiring from the utility grid and starts the generator. This occurs quickly, so there is very little down time.
The ATS also runs the generator periodically (called exercising) to ensure everything is working properly. If you hear the generator start the exercise cycle, don’t be alarmed—it doesn’t necessarily mean the power is off.
If natural gas is available at your house, that’s your best choice to power the backup generator. Natural gas engines run cleanly, require little maintenance and are relatively inexpensive to run. Also, if you have a gas furnace for heat, the size of the generator you’ll need is smaller.
Another clean-running fuel for a backup generator is propane, although it’s more expensive to use than natural gas. Many homes with electric heat have propane available for cooking. To power a whole-house generator, a larger propane tank would be needed.
A diesel engine-powered generator also requires a fuel tank. The shelf life of diesel fuel is only a couple of years even with a stabilizer—and the overall cost of installing a diesel generator will be higher. One advantage of using diesel, however, is that you can always pour more fuel into the tank if you need to run the generator longer than originally expected.
Another option is a smaller, less expensive, portable, gasoline-powered generator with several electrical outlets. These can provide enough electricity for the refrigerator and several lamps, plus enough power to operate the blower in a gas, propane or oil furnace for heat. Never attempt to plug this type of generator into an electrical output with a homemade double-male cord. This can back feed 120-volt current into the grid, which is dangerous for utility line crews.
You can get more information on backup generators from your local electric cooperative or a qualified contractor.
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These companies offer backup standby generators:
Baldor, (479) 646-4711
Coleman Powermate, (888) 977-2622
Cummins Onan, (800) 888-6626
Generac Power Systems, (888) 436-3722
Kohler Power Systems, (800) 544-2444