We generally think of the Oil Age as having begun around the start of the 20th Century. Henry Ford began production of the Model T in 1908, and British coal production would peak soon thereafter in 1913. And yet, despite the fast global uptake of oil through the first half of the century–and both world wars–it was not until 1965 that oil use in BTU terms overtook coal.
The chart you see here (click to enlarge) divides total global oil use in million tons by total global coal use in mtoe (million tons oil equivalent). This gives us BTU equivalency. As late as 1954 for example, the world was consuming 1054 mtoe of coal, yet only 673 mt of oil. I use this 10 year period of course because it shows the moment when, after 150+ years of coal use, oil finally overtook coal. In 1965 the world consumed 1480.9 mtoe of coal–and 1530 mt of oil.
So, when exactly did the Coal Age end, and the Oil Age begin? Well, I’ve recently spent time with energy data on global Wood, Coal, and Oil use back as far as 1800 and there are a number of insights to be gleaned. With regard to how global energy use was structured up until this time, it was revealing for example to see that the Great Depression hit global coal consumption very hard. Oil? Not so much. And for an obvious reason: oil was still young in its adoption. On the larger matter of energy transition, there are other good insights in the data. For example, the acceleration you see in this 10 year chart, when paired with the longer series back to say, 1854, confirms the idea that changes such as these happen slowly at first–and then (seemingly) all at once.