In the context of cellular respiration, specifically in the electron transport chain (ETC) during oxidative phosphorylation, the movement of electrons ultimately leads to the pumping of protons (H+) across the inner mitochondrial membrane and the generation of ATP.
Typically, it is said that for every 2 electrons that move through the ETC, 3 protons are pumped across the membrane, which can produce around 1.5 to 2.5 ATP, depending on the organism and conditions. The most common unit of energy produced is ATP, and thus the focus is more on the number of protons pumped rather than directly correlating a number of electrons to energy production.
To summarize, there isn't an exact number of electrons specified that correlates directly to a specific amount of energy because the processes are interrelated; electrons often come in pairs. However, the general understanding is that at least 2 electrons are required for a significant production of energy.
Thus, if the question is about the minimum number of electrons to move in a way that leads to energy production, the answer would be 2.