On March 6, at the start of the still-simmering trade war between the U.S. and Canada, hydropower generator Hydro‑Québec quietly stopped exporting electricity to New England.

At a time of year when Canadian hydropower typically supplies up to a tenth of New England’s power, the region has instead gone almost a month with virtually no cross-border flow of electrons.

Hydro‑Québec leaders say low prices in the New England market — not politics — are behind the decision to suspend sales. The disruption hasn’t affected power costs or reliability in the region yet, but some experts say it could if the cutoff extends into the summer cooling season. The situation also highlights a potential risk to state clean energy plans that count on Canadian hydropower to help offset fossil fuels.

“This shows the potential for the region to be vulnerable to manipulations of the supply,” said Phelps Turner, director of clean grid for the Conservation Law Foundation.

Hydro‑Québec’s main transmission line into New England, known as the Phase II line, stopped exporting any meaningful amount of power two days after President Donald Trump’s tariff on Canadian imports went into effect. Last March, by comparison, anywhere from a few hundred megawatts to more than 1,200 MW flowed along the line at any given time, making up between 5% and 10% of the region’s electricity use on average, Turner estimated.

The longer that New England needs to replace the absent hydropower, the more often it will call on natural gas or oil power plants to fill the gap with dirtier and more expensive electricity, particularly as demand increases in the summer and again next winter.

“Electrically, this is pretty much the most boring time of year, and certainly a much easier time of year to have a source go away or be on pause here,” said Dan Dolan, president of the New England Power Generators Association. ​“There is going to be both a cost and environmental consequence if we see this be a really durable situation.”

This pullback is likely due, at least in part, to ongoing abnormally dry and drought conditions in much of Quebec, which mean less water flow to power the company’s generators. Hydro-Québec, therefore, faces choices about what to do with the power it can generate, whether that means holding out for higher prices on the New England market or selling it domestically to meet the province’s own growing demand as it too electrifies in pursuit of climate goals.

“Hydro-Québec is proactively managing its energy reserves in the context of low runoff and, as such, will continue to limit its exports as it did in 2024,” said company spokesperson Lynn St-Laurent.

The lack of exports from Hydro-Québec coupled with the specter of fluctuating tariffs and counter-tariffs brings into focus the need for the New England grid to develop more stateside power resources and expand the infrastructure required to get energy where it’s needed, experts said.

“We’re going to need all the supply we can find, and part of that is going to come from Canadian hydro,” said Jeremy McDiarmid, managing director and general counsel at clean energy industry association Advanced Energy United. ​“We also need to be building things: We need to build transmission lines. We need to build new generation.”

Some are also concerned that ISO New England is not properly accounting for the declines in Canadian hydro supply. The grid operator’s planning process still uses the assumption that neighboring regions — mostly Quebec, Dolan said — will be willing and able to send 2,000 MW into New England at moments of exceptionally high demand, an expectation Dolan said ​“doesn’t strike me as responsible or appropriate reliability planning,” given the trend in the Canadian firm’s exports.