Jennifer Oldham reports for Bloomberg Businessweek about the conflict between the growing legal-marijuana industry and those who want to cut American energy use.

Pot’s not green.

The $3.5 billion U.S. cannabis market is emerging as one of the nation’s most power-hungry industries, with the 24-hour demands of thousands of indoor growing sites taxing aging electricity grids and unraveling hard-earned gains in energy conservation.

Without design standards or efficient equipment, the facilities in the 23 states where marijuana is legal are responsible for greenhouse-gas emissions almost equal to those of every car, home and business in New Hampshire. While reams of regulations cover everything from tracking individual plants to package labeling to advertising, they lack requirements to reduce energy waste.

Some operations have blown out transformers, resulting in fires. Others rely on pollution-belching diesel generators to avoid hooking into the grid. And demand could intensify in 2017 if advocates succeed in legalizing the drug for recreational use in several states, including California and Nevada. State regulators are grappling with how to address the growth, said Pennsylvania Public Utility Commissioner Pam Witmer.