TUMWATER, Wash. — Behind the covered windows of a nondescript two-story building near the Olympia Regional Airport, hundreds of marijuana plants were flowering recently in the purple haze of 40 LED lights.
It was part of a high-stakes experiment in energy conservation — an undertaking subsidized by the local electric company. With cannabis cultivation poised to become a big business in some parts of the country, power companies and government officials hope it will grow into a green industry.
The marijuana plants here, destined for sale in the form of dried flowers, joints or edible items, were just a few weeks from harvest and exuding the potent aroma of a stash room for the Grateful Dead. But the energy-efficient LED lights were the focus of attention.
“We wanted to find a way to save energy — that was important to us,” said Rodger Rutter, a retired airline pilot who started this indoor pot-farming business, Evergrow Northwest, after Washington State legalized recreational cannabis in 2012.
“We wanted to be able to offer the best product at the best price,” Mr. Rutter said, “and a big part of the cost is energy.”
As cannabis has increasingly gone legitimate — about two dozen states had already legalized it in some form before several others eased restrictions on Election Day — electric utilities have struggled to cope with the intensive energy demands of the proliferating industry.
Besides blown transformers and blackouts for utilities in some places, the ascent of Cannabis Inc. has also raised clean-air concerns in parts of the country where fossil fuels are still the main source of electric power.
Even in many places where growing marijuana plants is legal, cultivators are required to keep their crops out of public view. And in any case, many growers prefer having the ability to control the environment by raising the plants indoors.
Traditionally, indoor producers — formerly relegated to basements, garages and shadowy warehouses — relied on hot, high-intensity lights. When air-conditioning and ventilation were included, the energy used to grow a single marijuana plant would run seven refrigerators for the same period, according to one estimate.
But under an incentive program with the local utility here, Evergrow was able to install more than 100 sophisticated LED grow lights, hoping to reduce costs without sacrificing quality or yield. The utility, Puget Sound Energy, which gets about a third of its electricity from hydropower and most of the rest from coal and natural gas, offers grants to help customers offset the cost of energy-efficiency upgrades.
Although the LED lights are more expensive up front — they can run $1,600 each, as opposed to $350 for the high-pressure sodium lights traditionally used — their lower electricity requirements mean they can save money in the long run.
It is not just that the LED lights take so much less energy to operate. They also run cooler, requiring less air-conditioning.
“It’s a snowball effect,” Mr. Rutter said, surrounded by dozens of specimens with names like Lodi Dodi and Secret Recipe. “You just don’t suck up as much energy.”