What are the primary sources of energy?
Sources of energy include coal, petroleum, natural gas, nuclear, diesel, gasoline, and a variety of renewable fuels such as solar, wind, and fuel cells.1 Primary fuel sources vary in different regions of the country, depending on local resources and access to reliable supplies. The most commonly used fuel in the United States is petroleum. In 1999, it was the source of 40 percent of the energy consumed nationwide. The next two most commonly used fuels were natural gas and coal.2 In Connecticut, the top three fuel sources that year were petroleum, natural gas, and nuclear electric power. Very little coal is consumed in the state. Figure I-1 compares the market shares of the top fuel sources in the United States and Connecticut.3 (Petroleum is the primary source in all of the New England states, but the predominance of other fuels varies widely among the six states.) Trends. Figure I-2 presents a timeline showing the evolution of fuel sources used within the United States since colonial
