New England power plant air emissions increased in 2021

New England's power plants collectively emitted greater amounts of key air emissions in 2021 than in the year before, according to a report by the region's electric grid operator. Factors included the weather, decreases in power imported from outside the region, and increased reliance on coal and oil-fired generation.

The 2021 ISO New England Electric Generator Air Emissions Report provides "a comprehensive analysis of New England’s native electric generator air emissions (nitrogen oxides [NOX], sulfur dioxide [SO2], and carbon dioxide [CO2]), along with CO2 emissions associated with imported energy, and a review of relevant system conditions."

New England has significantly reduced the air emissions associated with its electric power sector over the past decades. According to the report, total average air emissions from "native generation" (in-region) have decreased overall during the 10-year span from 2012 through 2021: NOx by 39%, SO2 by 87%, and CO2 by 20%. The report credits the decline in emissions over this period to "shifts in the regional generation mix, with imports and wind generation offsetting decreases in coal-fired generation." 

Looking farther back to cover the 20-year span from 2001 through 2021, NOx emissions fell by 80%, SO2 emissions fell by 99%, and CO2 emissions fell by 41%. Summarizing these two decades of change, ISO-NE says, "The increased use of highly efficient natural-gas-fired generators, mandated use of lower-sulfur fuels, retirements of coal- and oil-fired generation, increasing amounts of wind and solar generation, and higher net energy imports have all contributed to the trend."

But on a year-over-year basis, emissions increased in 2021 relative to 2020 according to the grid operator. For native generation, NOx emissions grew by 2.9%, SO2 emissions grew by 12.2%, and CO2 grew by 7.8%. 

ISO-NE attributes the region's recent backsliding on emissions to several factors, including increased demand for native generation (due to a 20% reduction in imports), weather (warm summer, cold winter), and "the resource mix":

Coal- and oil-fired generation had year-over-year increases of 281% and 53%, respectively. Resources fueled by coal or oil produced more power than usual during colder weather in January and February 2021, and production by oil-fired resources also increased during hot weather in June and August. These resources, which have higher emission rates than plants fueled by natural gas, often contribute generation during peak energy demand periods in the summer, or when winter heating demand limits the availability of natural gas or drives up its price.

The grid operator expects continued growth in demand for electricity, as transportation and heating increasingly become powered by electricity.

New England electric demand projected to grow by electrifying heating and transportation

The operator of New England's electricity grid projects that demand for power will increase by 23% over the next 10 years "due to accelerating electrification of the heating and transportation sectors." State and federal policymakers are promoting "beneficial electrification", the replacement of carbon-emitting fossil fuel uses with lower-carbon-intensity electricity as a power source. The trend has potential to significantly decarbonize the region's transportation and heating sectors, which collectively emit many times more greenhouse gases than the region's electric power sector.

ISO New England's 2023–2032 Forecast Report of Capacity, Energy, Loads, and Transmission (CELT Report) presents the grid operator's perspective on the region's power system, including a long-term forecast for energy consumption and peak demand. To prepare the forecast, ISO-NE first develops a gross long-term forecast for electricity demand, based on factors including economic forecasts and weather data -- and increasingly on projections for the electricity needed to power electric vehicles and air-source heat pumps that are being added to the grid. ISO-NE then backs out its projection of energy efficiency and behind-the-meter solar photovoltaic production, to yield a net forecast.

According to the latest CELT report, gross annual electricity use is expected to grow by 2.4% annually over the 10-year period, while net annual use is expected to grow by 2.3% annually. EVs are expected to account for 13,961 GWh of grid demand in 2032, while heating electrification is expected to account for 7,334 GWh of demand that year. 

In terms of peak demand, ISO-NE expects significant growth in EV use, with transportation electrification is forecast to contribute 3,420 MW to the winter peak in 2032-2033. Heating electrification is forecast to contribute another 2,965 MW to the winter peak under average weather in 2032-2033, or 4,033 MW under colder-than-average weather. 

For comparison, in 2021 Maine's total net summer generating capacity was 5,026 MW, according to U.S. Energy Information Administration data. In other words, electrifying transportation and heating is projected to add more load to the region's grid than all of Maine currently consumes.