Q: We often have power outages during summer storms. I want to install a backup generator for the entire house. What size is best? Can I use it nonstop as a source of power rather than the utility company?
A: With the start of hurricane season, many people are interested in backup, or standby, whole-house generators to supply electricity during power outages.
These are different from the portable generators many people buy at home centers when a hurricane threatens. Portables operate off gasoline-powered engines and cost $300 to $1,500. You power household appliances by plugging them into extension cords plugged into the generator. Portable generators create deadly carbon monoxide and should never be operated indoors or in an enclosed area such as a garage, porch or lanai.
A permanently installed standby generator operates by providing power to a few selected circuits in your home. You plug the appliances you want to operate into those circuits. These cost $5,000 or more.
A standby generator, even a large one, is not designed to be used continuously in order to disconnect your home from the electric utility. It is designed to operate for only relatively short periods during power outages. Electricity from a standby generator is more expensive than electricity provided by your utility.
No matter what size whole-house generator you select (generation capacity is measured in kilowatts), it is best also to install an ATS (automatic transfer switch). This control switch senses when the utility's electric power stops or the voltage is too low during a brownout (often on a hot summer afternoon).
The ATS temporarily disconnects your house from the utility grid and starts the generator. This can take a short period to come up to full power. Without an ATS, you would have to do this manually, or a utility lineman might be shocked by your generator.
The size of standby generator you need depends upon how many electric items you want to operate during a power outage. A 12-kilowatt generator will handle a typical family's power needs. If you can get by without air-conditioning or hot water for a while, this will allow you to install a smaller, less expensive generator.
Total the wattages of all the electric items you think you need. The wattages of various appliances are listed on each appliance nameplate.
Keep in mind though, that many appliances with motors require greater starting wattages than the continuous usage listed on the nameplate. For example, a refrigerator using 700 watts may require up to 1,500 watts each time the compressor starts.
Most people select a natural gas standby generator if gas is available. It is clean burning and does not require a storage tank.
Propane is another common fuel. It also burns cleanly. Since the tank is on your property, the supply cannot be interrupted. It is more expensive than gas and it requires a tank.
Diesel fuel is less flammable and is easy to obtain. It requires an expensive tank and the shelf life of the diesel fuel is less than two years.
James Dulley is a mechanical engineer and do-it-yourselfer. Send questions to James Dulley, the Sensible Home, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to his Web site, www.dulley.com, to tour his energy-efficient home, post questions for other readers and find other information.