Overview of the Electric Power System
The electric power industry in the United States is composed mainly of "traditional" electric utilities, legal entities that, along with distributionfacilities, have the core purpose of delivering electricity to the public.Electric utilities can be investor-owned, municipal, state or federalutilities, as well as rural electricity cooperatives. The US electricity sectoralso comprises non-traditional participants, such as energy service providers,power marketers, independent power producers, and combined heat and powerplants.
In 2005, there were 3,133 electric utilities and 2,800 non-traditionalparticipants, operating a total of 16,807 electricity generating units, ofwhich 81.42% were in the Electric Power sector—that is, electric utilities andindependent power producers—with the rest in the Combined Heat and Powersector. Both sectors provided a total installed capacity of 1,067,010 megawatts[15, 16].
According to data reported by the United States Department of Energy[15, 16], it is estimated that the net generation of electricity increased by4.8% from 2002 to 2005, reaching 4,055 billion kW-h. The average annual rate ofincrease for the 12-year period from 1994 to 2005 was 2%. During the sameperiod, approximately 20% of the total electricity generation was provided bynuclear generation, while 65 to 68% of the total net generation was produced bycoal and natural gas. The contribution of electricity generated by natural gasincreased from 14.2% of the total in 1994 to 18.7% in 2005, whereas the shareof coal-fired generation to the total decreased from 52.1% in 1994 to 49.7% in2005. The decline in the contribution of coal to electricity generationreflects the fact that capacity additions in this period were preferentiallynatural gas-fired electricity generating units, especially since 2000.
Net generation from hydroelectric plants increased from 256 billion kW-hin 2002 to 270 billion kW-h in 2005 [15, 16]. However, despite this 5.46%increment, hydroelectric generation in 2005 was lower than the observed peak inthe preceding decade, when it reached 356 billion kW-h in 1997. The relativelylow hydroelectricity production has been attributed to the severe droughtsexperienced in the western United States from 1999 until 2004 [17]. Otherrenewable energy sources (biomass, wind, geothermal and solar technologies)contributed 2.3% of the total generation, with biomass comprising the majorityof this. The share of wind generation was 17.8 billion kW-h, nearly 19% of thetotal generated by all renewable energy sources combined.
Petroleum contributed 3% of the United States' electric generatingcapacity in 2005, producing 123 billion kW-h, while generation from othergaseous fuels (e.g., refinery gas, blast furnace gas) and other miscellaneoussources accounted for the remainder of electricity generation.
In summary, coal, nuclear and hydroelectric generating capacity in theUnited States remained relatively unchanged over the decade ending in 2005,while the installed capacity for natural gas and other renewable energy sourcesincreased considerably.