Popular Mechanics - USA (2019-12)

cal home with a 200-amp breaker
panel would need a 200-amp ATS.
Ultimately, generator size will
be based on the total running watts
and starting KVA of all the cir-
cuits, appliances, and mechanical
systems it supplies. KVA (kilo-volt-
ampere) is 1,000 volt-amps; think
of a volt as electrical pressure,
and an amp as electrical current.
Both numbers must be calcu-
lated: Running watts equals the
power consumed by an electrical
motor while running, and start-
ing KVA is required because each
time a motor starts, there’s a surge
that the generator must be able to
handle. Once standby electrical
circuits have been identified, the
electrician will add up the running
watts and starting KVA to project
the total electrical load and deter-
mine the proper-size generator.

■
SOUND AND SERVICE
Cities often have noise ordi-
nances for generators. A machine
may be rated at 62 decibels,
which doesn’t sound like a lot,
but imagine a neighbor idling a
Harley—tolerable in a rural area,
but not in the suburbs. Addition-
ally, most building codes require
generators to be at least five feet
from house openings and flam-
mable materials, making urban
installations tricky. Fuel-tank
placement is typically restricted,
especially near parking lots
and schools.
Generators need TLC, as most
complicated machines do. Like
cars, standby generators run non-
stop for many hours, so they have
to be maintained similarly.
A generator can last a lifetime
of outages if you check the oil daily
during use, run it at 75 percent of
its capacity, and avoid starting or
stopping it under load whenever
possible.

■

A COSTLY ENDEAVOR

Many factors determine the final

cost of a standby generator, which

makes pinpointing an exact price

difficult. A good general rule is

that the installed cost is usually

twice the price of the generator.

Be aware that there are two

basic engine operating systems:

air-cooled and liquid-cooled. Air-

cooled generators are smaller and

less costly, but they’re also louder,

even though liquid-cooled genera-

tors are typically larger.

Generally, a 22kW standby

generator is suitable for a home

that’s 2,500 square feet or smaller,

especially if it is equipped with

a gas range, a gas hot water

heater, and gas heat, which use

little electricit y. A 22kW air-

cooled generator can cost $4,500

to $5,000—or about $9,000 to

$10,000 installed.

Large-capacity, liquid-cooled

generators—in the 22kW to 45kW

range—cost between $10,000 and

$15,000, making the installed

price about $20,000 to $30,000.

Regardless which standby

generator you choose, it’s a sig-

nificant investment, but one that

many homeowners are willing to

make to keep their home safe and

comfortable.

2 LIGHTING CIRCUITS 200 W

4 LIGHTING CIRCUITS 400 W

10 LIGHTING CIRCUITS 1000 W

REFRIGERATOR 1200 W

SUMP PUMP 1000 W

WELL PUMP 1000 W

FURNACE FAN 500 W

GARAGE-DOOR OPENER 875 W

MICROWAVE OVEN 1000 W

ELECTRIC OVEN 2000 W

RADIO 50 W

TELEVISION 300 W

LAPTOP 45 W

DESKTOP COMPUTER 200 W

4 -TON CENTRAL AC 2500 W

COFFEE MAKER 900 W

WASHING MACHINE 1200 W

ELECTRIC CLOTHES DRYER 6750 W

TYPE OF LOAD WATTAGE

7KW

KEY

GENERATOR SIZE:

17KW

48 KW

A rough estimate

of energy loads

for typical home

appliances and

recommended

circuits for 7kW,

17kW, and 48kW

standby generators.

Generator Sizing Chart

38 December 2019

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