There is significant concern about the large amount of energy needed for Artificial Intelligence. AI and the computer processing power required to imitate human intelligence will require constructing new power plants to supply more energy. Compared to this, the energy efficiency of the human brain uses only 17 watts of power while performing functions that AI has not yet mastered. At the same time, the brain makes up only 2% of the body’s mass but consumes 20% of its energy.
The continuous flow of chemical reactions that keep the brain working is called metabolism. For brain cells to function, they need a constant supply of glucose that passes through the blood-brain barrier. If a person fasts for a long time or follows a ketogenic diet, the brain must switch to an alternative fuel source, which is ketones produced by the liver. As a secondary backup, the brain can also operate on lactate.
The brain transforms these energy sources into ATP (adenosine triphosphate). Neurons use ATP to generate electrical signals, which account for most of the brain’s energy use. Glial cells support neurons in various ways, such as breaking down glucose to provide energy.
During deep sleep, the brain’s metabolic rate decreases, but not as much as you might expect. When you are deeply engaged in complex tasks, your brain only uses about 5% more energy. The small difference exists because the brain is constantly performing “housekeeping” tasks, managing your body, and maintaining the functions of various organs and tissues. It continuously monitors your environment, pays attention to sights and sounds, and alerts you to issues that need attention.
After performing mentally demanding tasks, you might feel exhausted, but it could be due to tension. Your brain maintains a delicate energy balance across different neural regions, directing energy where it is needed. The energy efficiency of the human brain allows it to do everything with just 17 watts, while a supercomputer would need megawatts to perform the same tasks. It keeps your lungs breathing and your heart beating while you solve differential equations and think about what’s for dinner.
Artificial Intelligence can’t match the energy efficiency of the human brain. Your brain shows evidence of a designer God.
— Roland Earnst © 2026
References: biologyinsights.com and zmescience.com