How Much Power Does The Human Brain Require To Operate?

Neurogrid 65,536 artificial neurons packed onto just
one of Neurogrid's chips Rodrigo Alvarez 2009

From Popular Science:

Simulating the brain with traditional chips would require impractical megawatts of power. One scientist has an alternative.

According to Kwabena Boahen, a computer scientist at Stanford University, a robot with a processor as smart as the human brain would require at least 10 megawatts to operate. That's the amount of energy produced by a small hydroelectric plant. But a small group of computer scientists may have hit on a new neural supercomputer that could someday emulate the human brain's low energy requirements of just 20 watts--barely enough to run a dim light bulb.

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