(Newser) – Bad news for eco-conscious stoners: That joint you just smoked hurt the planet. Marijuana grown indoors accounts for 1% of America’s yearly electricity consumption, or $5 billion worth of energy, a study finds. That’s equivalent to the annual energy bills of 2 million homes. And in terms of CO2 emissions, puffing one joint is comparable to leaving a 100-watt lightbulb on for 17 hours, Fast Company reports.

That’s because of all the “lighting, dehumidification, air-conditioning, irrigation systems, space-heating, and ventilation systems” the plants require in order to grow indoors, the way dispensaries like them, writes Ariel Schwartz. Since growers have to keep a low profile, they don’t face pressure from consumers concerned about the planet. The solution? Legalize it. That way, “people will actually cast a critical eye on” the industry’s energy usage, Schwartz notes. (Read more marijuana stories.)

