"Indoor marijuana cultivation consumes enough electricity to power 2 million average-sized U.S. homes, which corresponds to about 1 percent of national power consumption, according to a study by a staff scientist at the Lawrence Berkeley National Laboratory.

Researcher Evan Mills' study notes that cannabis production has largely shifted indoors, especially in California, where medical marijuana growers use high-intensity lights usually reserved for operating rooms that are 500 times more powerful that a standard reading lamp.

The resulting price tag is about $5 billion in annual electricity costs, said Mills, who conducted and published the research independently from the Berkeley lab. The resulting contribution to greenhouse gas emissions equals about 3 million cars on the road, he said.

Narrowing the implications even further reveals some staggering numbers. Mills said a single marijuana cigarette represents 2 pounds of CO2 emissions, an amount equal to running a 100-watt light bulb for 17 hours."

Colin Sullivan reports for Greenwire April 11, 2011. [2]