This might sound like a silly question but in terms of energy efficiency how efficient are animals when compared to robots? Let's frame the question in the form of the ratio of total energy intake over the competitor's lifetime versus the amount of newtons of force it generates from birth to death. The energy spent on, say, maintaining a drone counts against it, as does the energy cost of extracting and refining the fuel it is fed. The competition ends when one of the two competitors dies.