This article is more than 2 years old.

December 3, 2015 This article is more than 2 years old.

As more states legalize marijuana in the US, pot cultivation is sucking up an ever-growing amount of energy from the grid.

Since most of the legal weed is grown indoors, the pot industry burns through large quantities of electricity used to power lamps, ventilation systems, and air conditioning. A square foot of planting requires some 200 watts of electricity (pdf, p. 20), about the same as a data center, according to a report this year in the Columbia Journal of Environmental Law.

The paper notes that marijuana plantations soak up at least 1% of the country’s electricity at a cost of $6 billion a year.

The US marijuana business has exploded in the wake of state efforts to legalize the drug. Sales increased 74% in 2014 to $2.7 billion, according to ArcView Group, which conducts research on the cannabis industry.

If all states legalized pot, the amount the industry spends on electricity could go up to $11 billion, High Country News notes.

That’s putting enough pressure on electric utilities that regulators discussed the issue at their annual meeting on Nov. 11, in a session titled “The Straight Dope on Energy & the Marijuana Industry.”

In Colorado, the first state in the US to allow the use of recreational pot, electricity use by the industry has been steadily growing since 2011, according to data presented by Xcel Energy during the meeting.

In Oregon, home pot growers have already caused several power outages. To prevent such incidents, a local nonprofit is providing marijuana farmers rebates to install more efficient lights, as well as technical advice.