VALLEY FORGE, Pa. — RTOs in the Northeast are experiencing diminished solar output and lower-than-expected loads as smoke from wildfires in Canada passes over the region.

“In recent days, smoke from wildfires in Canada has traveled to New England, significantly lowering production from solar resources in the region compared to what ISO New England would expect absent the smoke,” ISO-NE said in a statement Thursday.

Most solar generation in ISO-NE is behind-the-meter of retail loads, leading the smoke’s impact to manifest as increased energy demand in the region. Lower temperature from the smoke has had a counterbalancing effect, reducing energy consumption from air conditioning.

“These two factors — decreased production from solar resources and decreased consumer demand due to lower temperatures — [have] made forecasting demand for grid electricity challenging,” ISO-NE statement said. “In forecasting real-time and future demand for electricity, ISO New England relies on historical data from similar days, adjusting for changing system conditions. Because these smoky conditions are unprecedented in the region, there is little, if any, historical information to rely on, creating further complications in generating accurate forecasts.”

PJM spokesperson Dan Lockwood said the smoke has been having a similar effect as it passes over the mid-Atlantic region as well.

“Smoky conditions throughout the RTO this week have caused a reduction in visibility, reducing solar and keeping temperatures several degrees lower than usual. It is difficult to single out the effect of smoke alone, especially when PJM has not seen an expansive plume like this. However, the cooler temperatures and decreased visibility are similar to what we experienced during the period of July 19-21, 2021, when the RTO was covered with smoke from wildfires in the western U.S. PJM is closely watching the smoke maps and taking these factors into consideration as it forecasts load for its zones,” Lockwood said in an email.

NYISO reported total peak solar output over June 6 and 7 was 1,466 MW lower than forecast, including both utility-scale and behind-the-meter resources.

“Based on data compiled by NYISO forecasters, wildfire smoke cover significantly reduced incoming solar irradiance across the state on June 6 and 7. … While the haze caused by the ongoing Canadian wildfires had a significant impact on solar energy production, the two-day total peak production still reached 4,405 MW. The NYISO will continue to monitor this situation as it develops,” spokesperson Andrew Gregory said.

Jeff Weiss, executive chair of Distributed Sun, said one of their rooftop units in NYISO peaked at 63% of its nameplate capacity Thursday. A few weeks away from the summer solstice, he said solar should be operating at “full blast” this time of year, reaching full nameplate even at 75% solar irradiance due to the oversized inverters installed. While the lower output likely reflects the impact of the smoke, Weiss said upstate New York was expected to have reduced solar output to some degree due to wind, cloud cover and similar atmospheric conditions.

“While this extra particulate matter is certainly blocking out the sun, a detailed atmospheric analysis is required to accurately measure the specific impact of multiple factors,” he said.

A September 2020 analysis by the Energy Information Administration found that average solar output declined by 30% when smoke from wildfires covered California over the first two weeks of the month compared to the July average. Despite 659 MW in new utility-scale solar installations in the region, a 5.3% increase and an 11% growth in distributed solar, overall generation from solar was 13.4% lower for those weeks than in the corresponding period in 2019.

“In July 2020, daily solar-powered electricity generation, which includes generation from solar photovoltaic and solar thermal electric generators, ranged from 104 to 119 GWh, averaging 113 GWh for the entire month. Daily solar-powered generation began declining as large wildfires broke out in mid-August, reaching a low of 68 GWh on Aug. 22 before returning to approximately 100 GWh by the end of the month. Solar-powered generation began declining again as wildfire activity rose in September, falling as low as 50 GWh on Sept. 11 as PM2.5 smoke pollution increased,” EIA wrote.