Is your curiosity piqued? Good. This is an open question and one that cannot be answered, but appoximated at best. The question is, what is the sum total of Humankind's energy consumption throughout all of Humankind's historical existence? Okay, so now you see the enormous and virtually impossibility of calculating such a sum, given that said energy is used in so many different manners in society, and after all, our historical records are themselves subject to great debate and inaccuracy. For that reason, I think its best to treat this question as an interesting exercise, rather than a realistically calculatable scientific endeavor. I will try to break this problem down into what I think are the components of its sum. My defintion of how humankind consumes energy is this: Any energy used to sustain human life or build/maintain civilization. (I am open to other defintions) How humankind consumes energy... A list of some... 1) Human body energy consumption (food) - Nutritionists will tell you that the average caloric consumption of an average human is 2000 kCals/ day. Of course, this number could vary greatly throughout history as famines, smaller humans, diets and a plethora of other factors influence this average. Some people even today, in the less fortunate countries are malnurished and receive less that 1000 kCals/day, while others in the wealthy nations consume in excess of 3000 kCals/day. So, if we don't nitpick every detail, I think a historical average of 2000 kCals/day is fine for a ballpark estimate of an average human's food energy consumption. 2) Work animals - This is certainly open to debate, but I think its important to also include the contributions of work animals in our calculation of human energy consumption. After all, using an oxen to til your field, or a horse to transport your carriage is a means by which humans also use energy, albeit not internally generated (but neither is electricity for that matter, which we will get to). So we can thus include work animals in our calculation of humankind's energy consumption. 3) Electriciy - Since the day Edison invented electricity that we could readily use and distribute, we have been using electric power for everything from lightbulbs to computers. World (electrical) power consumption has been well recorded in the last 50 years and certainly contributes a large amount of humankind's energy consumption. 4) Oil, gas, wood, etc. - Cleary these 3 fuel sources and many others have contributed and still contribute to humankind's energy consumption. Oil fuels our cars, gas our homes, and wood our fires. I think this simplification is of how we use these fuels is fine for our estimation and the data for oil and gas consumption is fairly well logged during recent times. Of course, its impossible to know how many chords of wood were burned during history to fuel our fires and cook our roasts, but we certainly can imagine it has been alot. I am sure to have missed some other ways that human's have consumed power and leave them open for you to help fill in. Of course any estimate we would make on the historical aggregate of humankind's energy consumption is bound to be very inaccurate, yet still I think it is an interesting question to ponder and if we could get even within 3 orders of magnitude I think it would be a meritorious feat. Hopefully, you will help fill in some of the details so we can together try to tackle this question in a meaningful scientific way. Citing data is our best hope. Such as world electricity consumption data, world caloric consumption, etc. I think the best unit we should use as our base unit is the Watt(W). We can readily converts kCals and other energy units into the power unit of the Watt when we are ready to. My end goal would be having an estimate of humankind's historical aggregate power consumption in a fun an accessible phrase, like: Humankind has used 1,000,000 TerraWatts throughout history. Then we could make fun analogies like the Universe could have kept 100 light bulbs on for 10 billion years, or it could have let humanity use the power instead (this is an example and was not calculated correctly, but you get the point). So lets have some fun and tackle this question together!