Growing cannabis indoors requires a lot of electricity. Here’s what other states have found.

Got questions about Virginia’s laws on weed? We’ve got answers in our FAQs on the state’s cannabis policies.

If Virginia legalizes retail cannabis, those who partake will be indirectly imbibing coal, natural gas and uranium.

That will be because most cannabis would likely be grown indoors, and those are among the fuel sources that produce the electricity that would power those greenhouse lights. Of course, cannabis consumers would also be indirectly imbibing some sunshine and wind, along with some water and petroleum, but the point is that growing cannabis indoors requires more electricity — and across the country, the power demands for indoor cannabis are getting, umm, high.

I hate to harsh anybody’s buzz, but until Virginia converts to a purely non-carbon electric grid, retail cannabis would drive up the state’s carbon emissions. And, even with a non-carbon electric grid, retail cannabis would require more electricity produced by something somewhere — be it wind, solar, nuclear, whatever.

Don’t take my word on this. Here’s what Politico had to say last year in a story headlined “An inconvenient truth (about weed)”: “Marijuana has never been more popular in the U.S. — and its carbon emissions have never posed a bigger threat to the climate.”

OK, that sounds rather alarmist, and it’s well-known that smoking weed can make you paranoid, so let’s not take Politico’s word, either. How about the much more technocratic prose of the National Conference of State Legislatures, whose website contains this advisory: “The link between cultivation and energy consumption, although not commonly on a legislature’s agenda, is an issue becoming increasingly more relevant, especially with more states opening the door to both medical and recreational usage.”

That means us here in Virginia, where the General Assembly is currently debating whether to legalize retail sales of cannabis — and the supply chain behind those stores that would grow and process the plants that would go into joints, gummies and however else you choose to buy your jazz cabbage.

Let’s be clear: The General Assembly is doing more than debating the issue. The Democratic-controlled legislature will pass a legalization bill. The only questions at this point are what the details will say — and whether Gov. Glenn Youngkin will sign the measure. Given his druthers, he probably won’t; he’s made it clear he has no interest in cannabis. However, the governor also very much wants a sports arena in Alexandria and it could be that agreeing to cannabis is part of the legislative price he’ll have to pay for it. That will depend on just how much Youngkin really wants a deal, and how good Democratic legislators are at cutting a deal — because there are a lot of things other than cannabis that they’d like to see, too.

Most of the debate over cannabis has revolved around who would get licenses and how they’d be distributed — or whether we should legalize retail sales at all. I haven’t heard any discussion of the electricity demands that retail cannabis would set in motion, so let’s rectify that.

First, some basics. A 2021 study by the University of Vermont Law School found that only 11% of cannabis is grown exclusively outdoors, meaning the other 89% is grown either exclusively or partially indoors. There are definite advantages to growing cannabis indoors: You can grow year-round, you’re not subject to weather and pests, and you can better regulate the THC content that produces the buzz. You also don’t have to worry about weed thieves hauling off your crop in the middle of the night. 

The downside of indoor cultivation: It uses a lot of electricity.

Politico quotes an environmental consultant with the Colorado Department of Public Health and Environment: “For being such a ‘green’ industry, there’s some skeletons in the closet.”

For our purposes here in Virginia, let’s look at another relatively new industry whose power consumption has become controversial: data centers. Yes, let’s compare ganja with gigabytes.

Data centers account for about 2% of the energy usage in the United States, according to the U.S. Department of Energy.

By contrast, cannabis accounts for 1%, according to that University of Vermont study. Or maybe more.

The point being: Grow houses aren’t in the same range as data centers, but they do require a lot of juice nonetheless.

Here are some figures: In California and Washington state, two early adopters of legal marijuana, cannabis-related power consumption accounts for as much as 3% of the state’s total power usage, the University of Vermont found. Washington’s figures would be even higher, except that Washington, unlike other states, grows a lot of cannabis outdoors — at least 42%. 

In Denver, where much of Colorado’s cannabis is grown, the weed-related power consumption is about 4% of the total.

In Massachusetts, indoor pot accounts for 10% of that state’s industrial electrical usage, according to the Northeast Sustainable Cannabis Project. The key word there is “industrial,” so the study isn’t counting all the electricity used in Massachusetts. I haven’t found figures for what percentage of Massachusetts’ power is industrial versus other uses, but nationwide, it’s about 33%, according to the U.S. Energy Information Administration. That would put Massachusetts’ cannabis power consumption at about 3.3%, which is in line with California and Washington.

We obviously don’t know what Virginia’s weed consumption or production would be, so we don’t know how much power it will take, but is there any reason to think that Virginia would be different from these other states? 

Again, cannabis grow houses aren’t on the order of data centers — Dominion Energy says that 20% of its power now goes to data centers; the Northern Virginia Electric Cooperative says just over 50% of its power goes to data centers. (Disclosure: Dominion is one of our donors but donors have no say in news decisions; see our policy. You can be a donor and have no say, too.) Weed won’t be requiring that much power in Virginia, but grow houses will require some new power. In the aftermath of Colorado legalizing retail weed, Denver saw a power surge — and 45% of the increased electricity demand came from cannabis facilities, according to the Denver Post. In Portland, the advent of legal weed saw so much indoor cultivation that it caused seven blackouts, according to Pacific Power. More energy-efficient lighting might help prevent those kind of power spikes today, but the point remains — indoor cannabis is energy-intensive.

If you drew a Venn diagram, there’d probably be a big overlap between those who are most concerned about climate change and those who are fine with retail weed — in Virginia, both the Clean Economy Act and cannabis legalization have been pushed by Democrats. How do they reconcile cannabis legalization with the impact on carbon emissions? This has produced a lot of, shall we say, interesting discussions across the country. 

That whole University of Vermont report was aimed at studying “energy and equity in cannabis cultivation.” The report said many states and local governments have moved to impose certain restrictions on the energy that cannabis grow houses use. Ann Arbor, Michigan, requires cannabis cultivators to generate at least 10% of their power from on-site solar panels. Riverside, California, requires growhouses to generate at least 20% of their power on-site from renewable sources. Berkeley and El Dorado County, California, require cannabis operations to generate all their power from renewable sources. Boulder, Colorado, gives cannabis cultivators the option of producing 100% of their power from local renewable sources or paying a surcharge for cannabis-related electricity — “because of its proportionally significant contribution to climate change,” the county’s website says. 

The Vermont report fretted about both the energy consumption of cannabis grow houses — and how they’re often singled out for regulation while other industrial users aren’t. “If regulated cannabis cultivation is the only sector targeted for mandatory reductions in electricity consumption, that leaves out over 80 percent of the electricity used by indoor horticulture,” the report said.

Still, cannabis is more power-hungry than other indoor crops. Politico reports that cannabis grow houses need “40 times what it takes for leafy greens like lettuce, when grown indoors.”

I’m a little surprised there hasn’t been more discussion in Virginia about the power demands of indoor cannabis. The left is most inclined to worry about carbon emissions and the right is often inclined to warn that the grid can’t handle electric vehicles — you’d think both sides might want to ask some questions here. There is one obvious solution, however — one that Democrats ought to love because it would involve no carbon emissions and one that Republicans ought to love because it would bring jobs to rural areas they represent: Virginia could allow, even encourage, outdoor cultivation. 

As of now, the Senate version of the cannabis bill allows that; the House version would give state regulators the power to ban it. There are some good economic reasons to grow cannabis indoors, but there might be good environmental reasons — and political reasons — to make sure some of it’s grown outdoors.