Portable & Standby Generators

Portable generators are sold at home centers and tool companies and cost several hundred dollars to about $1,000. Most run on gasoline, though some run on propane in canisters, like backyard grills. With a portable generator, you can plug in heavy-duty extension cords (the number of outlets will depend on the generator) and run them directly to the equipment you consider most crucial. Or you can get by with a single extension cord if you install a power transfer switch in your house to direct the power to specific circuits.

To guard against carbon monoxide poisoning, you must run a portable generator outside and well away from windows and doors. Running it in the garage is also out because the exhaust can work its way inside even if the big door is open. And don’t even think of modifying an extension cord so you can plug the generator into a house outlet. Generator power needs to bypass the house wiring completely (by running extension cords directly to appliances) or go through a transfer switch, which also acts as a one-way gatekeeper that prevents the current from energizing your home’s transmission line and shocking an electrician working to restore power to your neighborhood.

Built-in standby generators are permanently installed outside, like air conditioners. Instead of running off gasoline, these generators run off natural gas or, where that isn’t available, propane. Assuming the connection isn’t to a tiny propane tank, either option means that standby generators can essentially run as long as they’re needed. Standby units also switch on and off automatically. And they are always wired to a transfer switch, so you never have to snake out extension cords. You can set up the system to power just a few circuits, or all of them, meaning you can weather a long power outage almost without changing your routine. Running a generator does add noise, though, although standby units are quieter than portables because they are more enclosed. Locating the generator in an insulated enclosure reduces the sound even more.

But the convenience of automatic standby power comes at a price: Installed units often come to about $10,000, though you can shave off a few thousand dollars by going with a small unit that powers just a few circuits.

In general, a 5,000-watt portable generator is the minimum that’s worth getting to back up vital systems. That’s enough for a fridge, a few lights and even a room air conditioner. Built-in systems start about 7,000 watts, but to keep central AC running, you’ll probably need 17,000 watts to 20,000 watts. Above that, the price jumps because higher-power generators need liquid coolant, not air.
(Wash Post, 7/18/2012)