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Tens of thousands of homeowners, on average, are without power on any given day, so buying a backup generator can be a good investment. These ten tips will help you chose the right one.
(Photo courtesy of Honda)
By the DIY experts of The Family Handyman Magazine
If you’re shopping for a portable generator—that is, one on
wheels that’s not permanently connected to your home’s electrical
system—a generator that supplies 5,500 watts is about
the right size. This is enough to power a few critical appliances
like a refrigerator, furnace, microwave, TV and some lights.
Of course, you can’t run a whole-house air conditioner and an
electric water heater at the same time with 5,500 watts, but a
generator this size will get you by until the power comes back
on. You can buy a good-quality 5,500-watt generator for about $700.
Portable generators are great in a pinch, but they’re often noisy and they
require frequent refueling. They also have to be stored when not in use,
and connected and started when the power goes out.
A standby generator is permanently connected to your home’s electrical
system and goes on automatically when the power goes out, providing
seamless power. Standby generators can run on propane or natural
gas, eliminating the need to monitor the fuel. And they’re quieter.
You can buy one large enough to power everything in your house, or you
can buy a smaller unit and choose the most critical circuits to power.
Standby generators start at about $1,800, plus installation. (And they do
need to be installed by a pro.)
The difference in cost between a portable generator and a standby unit
may not be as great as you think. Remember, a portable unit requires either
expensive extension cords or a transfer switch. Standby units can run on less expensive natural gas, which will save you money in the long run.
When it comes to portable generators and ease of
use, liquid propane (LP) sure beats gasoline. Gasoline is a
handy fuel, but it’s not without problems. Storing enough
gasoline to get you through a several-day power outage
requires constant vigilance. First you have to buy several
5-gallon gas containers and find a safe place to store them.
Then you have to add stabilizer and ideally replace the gas
after several months to make sure it’s still fresh when you
Propane-powered portable generators solve these problems
and more. You can store and use liquid propane (LP)
indefinitely (it doesn’t go bad). Refueling is simple and safe;
just replace the propane tank with a full one. And you don’t
have to worry about the carburetor on your generator getting
gummed up with old gasoline. Search online for “propane generators” to see what’s available.
You may find a great deal on a generator by shopping
online. But what will you do if you can't get it serviced
locally? Sometimes it's worth spending a little extra to buy
from a local dealer. Parts will be available, and the dealer
will be familiar with maintenance and repair procedures for
your model. So before you buy a generator, make sure
there’s someone nearby who can provide parts and service.
You can use extension cords from your portable generator to
power any device with a plug, but anything that’s directly connected
to your home’s wiring, including essentials like your well
pump, furnace and electric water heater, requires a transfer
A manual transfer switch is essentially a small circuit breaker
box that you mount next to your main electrical panel. You match
the capacity of the transfer switch to the wattage of your generator.
Then you choose which circuits to connect to the transfer
switch. The Gen Tran manual transfer switch shown here
came prewired for six circuits and included the inlet box (generator
connection) and the cord to connect the generator.
A transfer switch is the only safe way to connect your generator
to house wiring because it requires you to disconnect the
house wiring from the incoming power lines at the same time
you switch to generator power. This prevents the possibility of
“backfeeding” generated power into the power lines, which creates
a potentially lethal hazard for power line workers.
Connecting a manual transfer switch is an advanced electrical
project. An electrician should be able to complete an installation similar to the one shown here in about three hours.
If you’re the adventurous type, you can just go with our
recommendation of a 5,500-watt generator and make
the best of it. But if you really want to know what size
generator you need to power everything you want, then
the only way is to add up the wattage of all the lights,
appliances and motors that you intend to run
Generator manufacturers and resellers have charts
you can refer to that list the average wattage used for
various appliances and motors. Or you can check the
nameplates on the appliances you want to power. If
wattage isn’t listed, you can derive it by multiplying
volts by amps. For example, if the plate lists 2.5 amps at
120 volts, multiply the two to get 300 watts.
There’s one caveat, though. Motors require an extra
surge of electricity to get started, and you have to factor
this into the equation. Add up the wattage of everything
you want to run. Then determine the largest motor you
need to run (the furnace, for example), multiply the
wattage requirement by 2 to get the approximate startup wattage required, and add this number to the total.
A 5,500-watt generator will run about eight hours on 5
gallons of gasoline, so gas management is critical if you
want to be prepared for an extended power outage.
That may mean running your generator for shorter periods
and coasting on things like refrigeration.
Having several filled 5-gallon gas cans available is
prudent, but you’ll need to add stabilizer to extend the
shelf life. Even then, after six months or so you should
pour it into your car’s gas tank and refill the cans with
fresh fuel. The generator itself should be run dry for storage
or filled with stabilized fuel. That fuel should be replaced every six months as well.
Remember, if you decide not to install a manual transfer
switch, you'll need a lot of expensive, heavy-duty extension
cords. Using undersize cords presents a fire hazard and can
damage motors as well as stress your generator. To run a
refrigerator, depending on how energy efficient it is and how
far from the generator, you'll need at least a 12-gauge cord. A
50-ft. 12-gauge cord will set you back about $50. Multiply that
by five or six and you can see that a transfer switch starts to
sound like a better deal.
Computers, TVs and many modern appliances
contain sensitive electronics that can be damaged by
the “dirty” power produced by less expensive generators.
Inverter-type generators provide the cleanest
power but are very expensive, especially in sizes large
enough to power a house. But for a little extra money,
you can buy generators with power conditioning that
provides cleaner power. Total Harmonic Distortion
(THD) is a way to measure the quality of electricity from
a generator. Look for a generator with a THD of less than 5 percent to safely operate most electronics.
One problem with portable generators is the noise that
you—and your neighbors—have to put up with. You can
compare decibel ratings to find quieter models, but
keep in mind that there’s no industry standard, so you
may be comparing apples and oranges. Standby generators
are quieter, and for a stiff premium you can buy
a really quiet portable generator like the 6,500-watt Honda shown here.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.
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