That’s the title of a Wikipedia article. It discusses the question how much work it would be for a human to provide one (1) kWh.
That article is not very clear, but it cites this article on the subject by Jean-Marc Jancovici, which I found interesting. He tries to estimate how many people the average French person would need to employ to get the 30,000 kWh per year a French consumes. His result is between 400 and 500, not counting energy contained in imported goods, which would add another 100 to the score.
I have discussed this earlier, at the time reporting that one kWh corresponds to eight hours of very hard human work.
Have that in mind when you hear that electricity for new large scale solar projects will cost less than 9 cents euro from July on in Germany.
Could you find 500 people to work very hard for you a whole day for 9 cents? Even if you could, you would need to pay much more in food than those 9 cents. In contrast to solar panels, humans don’t run only on sunlight. They need fuel (food).
The whole point here is that energy is extremely cheap in our Paradise Era compared to all of human history until a couple of hundred years ago.