If Ontario Premier Doug Ford follows through on his threat to cut off electricity to 1.5 million U.S. homes and businesses, the province will need to reduce its own power production.

On Monday, Ford announced a 25 percent surcharge on electricity exported from Ontario to Michigan, Minnesota, and New York. This move is in response to the U.S. tariffs imposed on Canadian goods. The surcharge, expected to generate up to $400,000 per day, may just be the beginning of the dispute.

“If the United States escalates, I will not hesitate to shut the electricity off completely,” Ford said, intensifying the stakes of the ongoing conflict.

However, fully cutting off energy exports to the U.S. would require Ontario to reduce its own electricity output. Ford clarified that the province would likely need to scale back its hydro-electric production, as halting nuclear power generation could take months. “We just have to reduce the amount of energy we’re outputting right now, and it wouldn’t be nuclear because if we turn down the nuclear reactor it could take six months but hydro, we could slow that down,” Ford explained.

Ontario’s energy system, managed by the Independent Electricity System Operator (IESO), relies on its agreements with the U.S. for the “affordability, reliability, and sustainability” of its electricity grid. Reducing exports could create significant challenges for both Ontario and its U.S. counterparts.