The graph shows for 10 countries the historical growth in energy access. In 1920, only 35% of Americans had energy access (here shown as "electricity access" defined as "household electrification"). This total reached 100% by the mid-1950s. In contrast, Mexico was at about 35% access in 1930, and has yet to get all the way to the 100% mark. China went from 35% in 1970 to 100% by about 2005, a very similar rate to that of the United States. You can see India is following a much shallower trajectory, going from about 25% in 1980 to 65% in 2010.
How fast can energy access occur? These data provide some insight into that question.