While petroleum still reigns supreme today, within one to two decades, natural gas might surpass it as the dominant energy provider. In fact, recent trends suggest that another transition is already underway. In particular, while petroleum and coal consumption have dropped steadily since 2006, natural gas consumption has increased.

For a century, oil and natural gas consumption trends have tracked each other quite closely. Figure 2 shows normalized U.S. oil and gas consumption from 1920 to 2010 (consumption in 1960 is set to a value of 1.0). These normalized consumption curves illustrate how closely oil and gas have tracked each other up until 2002, at which time their paths diverged: natural gas consumption declined from 2002 to 2006, while petroleum use grew over that time period. Then, they went the other direction: natural gas consumption grew and oil production dropped. That trend continues today, as natural gas pursues an upward path, whereas petroleum is continuing a downward trend.