New England, where the project will be located, doesn't use very much coal at all (usually less than 1% of generation recently). Mostly it's natural gas, nuclear, hydro from Canada, and renewables.

https://www.iso-ne.com/isoexpress/web/charts

On very cold winter days we do use a fair amount of oil for power generation, but that's typically limited to just a handful of days a year when we can't get enough natural gas due to pipeline constraints.