Spherical Energy, or Genkidama for Japanese Dragon Ball Z name lovers, is one of Goku's strongest techniques. He's used it multiple times throughout the series, perfectly silencing the toughest enemies like Freeza, Majin Buu, and the dragon Li Shenron. IS I notice that it takes a lot of energy to accumulate to use it.
Exactly but how much energy must be given to goku to create the genkidama sphere? Not a trivial question as it has never been given a value in Dragon Ball Z that can help understand the situation. It is known only from a few sentences that giving up one's energy to Goku means getting very tired, as if there was a great physical exertion.
dr Yanagita is a very popular researcher in Japan who often dives into the analysis of anime, manga, and fictional works to find a scientific explanation. He elaborated on Goku's Genkidama, explaining that "a human body is primarily composed of oxygen, carbon, hydrogen, and nitrogen. If Majin Buu was composed the same way (not a given) and weighed around 100 kg, then destroying it at the atomic level would be it Energy equivalent to burning 250,000 tons of oil is required."
On Dragon Ball Z's Earth, we can assume that there are around 10 billion people, including the Namekkians and someone else who can contribute by giving Goku his energy. Following the logic of Dr. Yanagita means dividing 250,000 tons of oil by 10 billion an average contribution of 270 kcal. It means that every human must Donate energy that corresponds to the consumption of 3.8 kilometers. So yes, it is certainly very tiring.
And would you be willing to donate your energy to Goku to create this giant Genkidama?