Frequently Asked Questions - Power
Hoover Dam provides generation of low-cost hydroelectric power for use in
Nevada, Arizona, and California. Hoover Dam alone generates more than 4 billion
kilowatt-hours a year - enough to serve 1.3 million people. From 1939 to 1949,
Hoover Powerplant was the world's largest hydroelectric installation; today, it
is still one of the country's largest.
Hydroelectricity is a clean, renewable source of energy that does not result
in air pollution, chemical runoff, or toxic waste disposal.
Where is the powerplant located?
In a U-shaped structure at the base of the dam. Each powerplant wing is 650
feet long. In all of the galleries of the plant there are 10 acres of floor
What is the capacity of the Hoover Powerplant?
There are 17 main turbines in Hoover Powerplant. The original turbines were
all replaced through an uprating program between 1986 and 1993. With a rated
capacity of 2,991,000 horsepower, and two station-service units rated at 3,500
horsepower each, for a plant total of 2,998,000 horsepower. The plant has a
nameplate capacity of about 2,080 megawatts. This includes the two
station-service units, which are rated at 2.4 megawatts each.
How does the water reach the turbines?
Through four penstocks, two on each side of the river. Wicket gates control
water delivery to the units.
Under what heads do the turbines operate?
Maximum head (vertical distance the water travels), 590 feet; minimum, 420
feet; average, 510 to 530 feet.
When were the power installations in the plant completed, and of what
do they consist?
Installation was completed in 1961. With the uprating completed in 1993,
there are fifteen 178,000 horsepower, one 100,000 horsepower, and one 86,000
horsepower Francis-type vertical hydraulic turbines. There are thirteen
130,000 kilowatt, two 127,000 kilowatt, one 61,500 kilowatt, and one 68,500
kilowatt generators. All machines are operated at 60 cycles. There are also
two 2,400 kilowatt station-service units driven by Pelton water wheels. These
provide electrical energy for lights and for operating cranes, pumps, motors,
compressors, and other electrical equipment within the dam and powerplant.
How was the powerplant machinery transported from the canyon rim to
An electrically operated cableway of 150 tons rated capacity, with a
1,200-foot span across the canyon, lowered all heavy and bulky equipment. The
cableway is still used when necessary.
How much energy does Hoover Powerplant produce on a yearly
The average annual net generation for Hoover Powerplant for 1947 through
2005 was about 4.4 billion kilowatt-hours. The ten-year annual average for
1996 through 2005 was about 4.8 billion kilowatt-hours. The maximum annual net
generation at Hoover Powerplant was 10,348,020,500 kilowatt-hours in 1984,
while the minimum annual net generation since 1940 was 2,648,224,700
kilowatt-hours in 1956.
What is a kilowatt-hour?
It is a unit of work or energy equal to that done by one kilowatt of power
acting for one hour. A kilowatt is 1,000 watts or 1.34 horsepower.
Who operates and maintains the powerplant?
The powerplant is operated and maintained by the Bureau of Reclamation.
Who are the principal contractors for energy?
The States of Arizona and Nevada; City of Los Angeles; Southern California
Edison Co.; Metropolitan Water District of Southern California; California
cities of Glendale, Burbank, Pasadena, Riverside, Azusa, Anaheim, Banning,
Colton, and Vernon; and the city of Boulder City, Nevada.
How is the firm energy generated at Hoover Dam
Arizona - 18.9527 percent
Nevada - 23.3706 percent
District of Southern California - 28.5393 percent
Burbank, CA - 0.5876
Glendale, CA - 1.5874 percent
Pasadena, CA - 1.3629
Los Angeles, CA - 15.4229 percent
Southern California Edison Co.
- 5.5377 percent
Azusa, CA - 0.1104 percent
Anaheim, CA - 1.1487
Banning, CA - 0.0442 percent
Colton, CA - 0.0884
Riverside, CA - 0.8615 percent
Vernon, CA - 0.6185
Boulder City, NV - 1.7672 percent
How is the income from the sale of energy used?
To pay all operation and maintenance expenses and to repay the major part
of the construction cost of the dam and powerplant, at interest not exceeding
3 percent. The cost of construction completed and in service by 1937 was
repaid on May 31, 1987. All other costs, except those for flood control, will
be repaid within 50 years of the date of installation or as established by
Congress. Repayment of the $25 million construction cost allocated to flood
control is currently deferred. In addition, Arizona and Nevada each receive
$300,000 annually in lieu of taxes.
What are the primary parts of a generating unit?
The exciter is itself a small generator that makes
electricity, which is sent to the rotor, charging it with a magnetic
The rotor is a series of electromagnets, also called
poles. The rotor is connected to the shaft, so that the rotor rotates when the
The stator is a coil of copper wire. It is stationary.
The shaft connects the exciter and the rotor to the
Water strikes the turbine causing it to spin. Hoover Dam
uses Francis turbines.
How is electricity made?
Electricity is produced as the magnets of the rotors spin past the
stationary wiring of the stator. This concept was discovered by scientist
Michael Faraday in 1831 when he found that electricity could be created by
rotating magnets within copper coils.
Source - U.S. Department of the Interior - Bureau of Reclamation