Energy use in Mendocino County has risen 27 percent — more than three times the state's average — since medical marijuana was legalized in 1996. Humboldt County's usage has risen 51 percent, more than six times the state's average, according to PG&E.
Growers and law enforcement officials attribute the spike to indoor pot growing, which requires energy-sucking fans, air filters and high-intensity lights.
Indoor pot gardens can use as much as 20 times the electricity as the average household, said Peter Lehman, director of Schatz Energy Research Center at Humboldt State University.
Statewide, energy consumption per household has increased 8 percent since 1996. Sonoma County's energy use rose by 9 percent, while Lake County's rose by 14 percent.
Indoor marijuana gardens have come under fire as wasteful, hypocritical and unnecessary, since marijuana already grows like a weed in the North Coast's Emerald Triangle.
"Plants are the original solar collectors," Lehman said. "They're very good at it."
Lehman said the problem is "particularly egregious here. It's expensive, it's bad for the environment, and it's wasteful. It's a misuse of a precious energy resource."
"It's amazing," said Matthew Cohen, executive director of Northstone Organics Cooperative Inc. in Mendocino County, a medical marijuana collective. "You have these progressive liberal folks who eat organic and maybe even drive a Prius but continuously burn 8,000 watts."
Northstone grows its plants outdoors and in greenhouses.
The average California household used 561 kilowatt hours in 2009, according to PG&E. In Humboldt County, the average was 673 kilowatt hours, and among PG&E's Mendocino County customers, it averaged 768 kilowatt hours.