Transportation and Electricity Transmission - Energy Policy Analysis: A Conceptual Framework - page 210

Figure 13.3 Sources of U.S. Electricity Generation, 2010

Petroleum
0.90%

Geothermal
0.40%

Solar 0.02%

Biomass 1.40%

Wind 2.30%

Hydro
6.30%

Coal 44.80%

Nuclear 19.60%

Natural gas 24.00%

Source: USEIA 2011b, Table ES1.

at 0.4 percent, and solar (thermal electric and photovoltaic) at 0.02 percent of total U.S. electricity
generated in 2010.
The portion of electricity produced by renewable sources is increasing rapidly, but is still small.
The trend in recent years in the electric utility industry for construction of new capacity has been
overwhelmingly in favor of natural gas, and away from oil and coal, with renewable sources of
energy only beginning to make inroads. Boilers at many former oil-fired plants were converted
to natural gas in the previous twenty years. Wind energy has been the fastest growing segment of
renewable sources since 1999.
At the beginning of the twentieth century, there were over 4,000 individual electric utilities,
each operating in isolation. Almost all of them used low-voltage connections from nearby power
plants to distribute electricity to local customers. As the demand for electricity grew after World
War II, electric utilities interconnected their transmission systems. Coordination over a wide area
may minimize operating costs and capital expenditures for plant construction, enhance system
stability and recovery capabilities during emergency operating conditions, and provide oppor-