Terms like "renewable energy" and "clean energy" mean different things in different places at different times, and Canadian hydropower is in a grey zone that sometimes counts and sometimes doesn't.
Even at the federal level, Canada and the United States use the terms differently. Natural Resources Canada, a Canadian federal agency, uses something like a dictionary definition of renewable energy: "Energy derived from natural processes that are replenished at a rate that is equal to or faster than the rate at which they are consumed." It puts hydropower on the same level as solar or wind.
In the United States, the Environmental Protection Agency defines renewable energy similarly, as "resources that rely on fuel sources that restore themselves over short periods of time and do not diminish."
But it also makes an interesting distinction. Large-scale hydropower is, by definition, renewable power. But it's not green power.
"Green power is a subset of renewable energy and represents those renewable energy resources and technologies that provide the highest environmental benefit," a term that allows only for "low-impact small hydroelectric resources," according to the agency.
"Some renewable energy technologies can have an impact on the environment," the Agency continues. "For example, large hydroelectric resources can have environmental trade-offs on such issues as fisheries and land use."
The U.S. Energy Information Administration goes further, by underscoring the carbon and methane emissions associated with large scale hydropower.
"Greenhouse gases such as carbon dioxide and methane may also form in reservoirs and be emitted into the atmosphere. The exact amounts of greenhouse gases that form in hydropower reservoirs is uncertain," it writes. "The greenhouse effect from the emissions from reservoirs in tropical and temperate regions, including the United States, may be equal to or greater than the greenhouse effect of the carbon dioxide emissions from an equivalent amount of electricity generation with fossil fuels."
At the state level, the benefits of large-scale hydropower have also been only tepidly embraced by regulators.
For years, various New England states have been using both incentives and mandates to push utilities to increase their "renewable energy portfolios."
When Maine first created a renewable energy portfolio in the early 1990s, it "was new and leading edge public policy," according to former Maine State Sen. John Cleveland, who served his first stint in the statehouse from 1990 to 1998.
Cleveland introduced a landmark bill that changed how Maine's electricity industry would be regulated, and also created the first mandatory renewable energy portfolio requirement.
The purpose, he said in a recent interview, "was to create a market for renewable energy produced and consumed in Maine."
Under Cleveland's bill, only small-scale hydropower, generating 100 megawatts or less, qualified. But Cleveland said the size limitation was less about the environment, and more about protecting Maine's economy.
"We did not want a single or just a few large generation facilities to take the entire portfolio limit. We wanted a diversified renewable portfolio and we wanted to encourage and protect Maine sourced renewable power throughout Maine," he said. "This would help ensure that the power assets and related jobs were located in Maine."
Cleveland also said his law wasn't designed to address the environmental effects of transmission corridors or Canadian dams.
"When we were drafting the legislation, we obviously could not know what all projects were, and what the environmental impacts would be," he said. Instead, he envisioned that the impacts would be considered by the Public Utilities Commission.
In 2010, Maine reaffirmed that hydropower generation facilities would have to be capped at 100 megawatts to be considered for meeting renewable energy portfolio standards, and that standard remains.
Vermont, which leans heavily on Canadian hydropower and is facing down an ambitious mandate of achieving 90 percent renewable energy by 2050, changed its renewable energy definitions in 2010, when then-Gov. Jim Douglas signed An Act Relating to Renewable Energy. The law made Vermont the only state in the nation to define Canadian hydropower as renewable energy, under the state's renewable energy portfolio.
Massachusetts adopted its first standards for renewable energy portfolios in 1997; in 2008, and again in 2018, it reaffirmed that hydropower plants had to be smaller than 7.5 megawatts for some types of incentives, and none could be larger than 30 megawatts to qualify. Qualifying generators also had to be identified as "low impact" by the Low Impact Hydropower Institute.
But in 2016, when Massachusetts lawmakers wrote An Act to Promote Energy Diversity, the emphasis shifted from small and low-impact, to robust and reliable.
"Instead of using that definition of 'renewable energy,' which was established in reference to the Renewable Energy Portfolio Standard ... the legislature created a new definition of 'clean energy generation' to refer to large-scale hydropower," according to Thomas B. Ashe, research director for the office of Massachusetts State Rep. Michael Finn, who chairs the House Committee on Global Warming and Climate Change.
That change drove the Massachusetts request for proposals for large scale energy procurements, which in turn led to Hydro-Quebec's efforts to get 1,200 megawatts of electricity through Western Maine, and on the way to power 1.2 million Massachusetts homes.