This page describes major observations, findings, and insights to be gained by understanding how the U.S. energy system has grown and changed over time.

Energy transitions in U.S. history

1. U.S. energy history is not just a story of growth. As we think about future transformations, it’s important to realize that we have already experienced changes as momentous as anything proposed today. Coal, for example, has been through a rollercoaster evolution: it began as a minor fuel, rose to become the main energy source in every sector in the early 1900s, then was replaced in most sectors almost completely by oil and natural gas. Coal use survived in the small electric sector, rose again when electricity boomed in the 1960s, and now is declining sharply, replaced by cheap natural gas.

   Action: Drag the slider from 1800 to 1918 and watch coal become dominant in every sector. Then drag to the 1960s and watch coal eradicated from one sector after another. After the 1960s, watch as coal use powers the growth of electricity, and then falls from 2005 as it is replaced by cheap natural gas. (See also the industrial and residential sector figures.)

2. The U.S. was only able to move beyond farming when railroads made coal widely available. For most of the 1800s, the U.S. had essentially no industry. We were a rural, farming nation; our only real exports were cash crops like cotton, wheat, and tobacco. Industry developed only after the Civil War when the expanding railroad network could carry coal throughout the country. The steel industry in turn grew to help build the railroads.

   Action: Note that the industrial sector was tiny before the 1860s. Drag the slider from 1860 to 1900 and watch as industry grows, powered by coal. See also the industrial sector figure.

3. The U.S. is currently in the middle of an energy transition. Fracking, which made natural gas cheap, has produced a transition in electricity as important as past historical transitions. Coal use has dropped by half in just over a decade and coal mines are shutting down. The replacement of coal has in turn led to a major drop in energy use, because combined-cycle natural gas power plants are more efficient than their coal counterparts. Since 2005, U.S. per capita energy use has shrunk by 13%, about half of which is due to this increase in generation efficiency. For electricity customers, all this turmoil and change is likely passing unnoticed.

   Action: Slide from 2000 to 2019 and watch the proportion of fuels into the electricity box (at the top) shift away from coal and toward natural gas. Note also that the primary inputs into the electricity box decrease, even though the electricity output is fairly stable. See the figure on electricity generation efficiency.

4. The U.S. has been electrifying for a long time — except in transportation. Since Edison’s first sales of electricity in 1882, an ever-increasing fraction of U.S. primary energy has been converted to electricity before end use: 2% in the 1910s, over 20% in the 1970s, and now 34% in 2019. Every sector has become more electrified except transportation, where use of electricity actually fell. In 1900, a third of all cars were electric, compared to only 1% in 2019.

   Action: Slide from 1882 to 1960 to see the slow initial growth of electricity, and slide through the 1960s, when electricity boomed as the grid was built out. Note how electricity becomes important in every sector other than transportation. See sectoral figures for residential, industrial, and agriculture and compare with transportation. Per capita electricity use in transportation peaks in the 1920s, the golden age of electric streetcars.

How much energy do we use?

5. The U.S. has a long history of wastefulness. In 1800, Americans were about as wealthy as Europeans but used about four times as much energy per person, mostly because households burned enormous amounts of wood. In 2019, Americans still use around twice as much energy per person as contemporaries like the British or French with similar wealth levels.

   Action: See also our figures on energy intensity, showing a drop from very high values. On the Sankey, scroll between 1800 and 2019 and note that in two centuries, energy use grew only 3×. Energy use in the early 1800s was very high relative to GDP: during this same period the economy grew by 25×.

6. Modern farming is not especially energy-wasteful. Modern industrialized agriculture actually uses less energy per capita than farming in the 1800s, because of the high energy needs of the horses that pulled farm equipment. Unlike a tractor, a horse cannot be turned off when not working. Our results show that modern farming is lower-energy even with new use of energy-intensive indoor animal husbandry and industrial fertilizer. These results also mean that over all U.S. history, the energy inputs of farming have exceeded the energy content of the food produced.

   Action: See figures on agricultural energy use. Agricultural energy use is so small that it is hard to see on the Sankey diagram.

Lessons about energy transitions

7. The effects of energy crises are longer-lasting than those of financial crises. Financial crises (the Great Depression of the 1930s and the Great Recession of 2008) and energy crises (coal in the 1910s and oil/gas in the 1970s) both appear in our dataset as sharp drops in energy use. Drops during financial crises were temporary and caused no structural changes in the energy system. By contrast, the 1910s and 1970s energy crises fundamentally reshaped the energy economy. Both involved price spikes and shortages, turning a period of rapid growth in use of a fuel into a long-term decline, and both led to a long-term reduction in the energy/GDP ratio. Neither coal nor oil ever recovered to their pre-crisis peaks in per capita usage.

   Action: Slide from 1910 to 1950 and 1973 to the present, and note how these crises cause coal and oil use respectively to peak and decline. (See our graph displaying the sectoral evolution of energy use, in which 1929 and 2008 are only temporary blips. See also our figures on energy intensity — energy crises show up as changes in slope but financial crises are barely visible.) (WWII is also barely visible, though it caused a strong increase in energy use.)

8. Once energy infrastructure is built, transitions can be very fast. Energy transitions cannot occur until infrastructure allows widespread use. Coal, petroleum, and natural gas were all used for decades at a small scale, especially near the mines and wells of energy-rich Pennsylvania, before they could make a national impact. National expansion was only possible after expansion of railroads (1860s) and pipelines (early 20th century for oil, 1940s–50s for gas). Once supply infrastructure exists, transitions can be rapid. U.S. household heating, for example, switched in under a decade from coal to largely oil and then gas.

   Action: For a very obvious example of asymmetric transition speeds, look at the residential/coal figure: the adoption of coal for home heating began early and proceeded slowly until the creation of the railroad network; the adoption of oil began late and took less than a decade.

9. The government has long played a heavy role in U.S. energy development. Key energy infrastructure in U.S. history has often been subsidized or directly built by the federal government. The government helped build railroads (1860s), pipelines (1940s), and the electrical grid (1940s–1960s). It directly built hydroelectric dams (1930s) and the national interstate highway system (1950s). Federal and state regulators set consumer prices in railroads (1880s), coal (1910s), and electricity (today). New energy technologies were directly funded (nuclear, 1950s), subsidized (wind and solar, today), or mandated (ethanol, today) by federal and state governments. Reliable energy supply has long been seen as a national priority.

   Action: Click on milestones (visible as circles on the slider) in 1862, 1887, 1933, 1956, 1978, 1992 for more details on various government interventions.