U.S. and Canadian power system operators are beginning to see effects of the coronavirus pandemic, but isolating those impacts from weather-related load fluctuations remains challenging.

Grid operators such as the Midcontinent ISO and ISO New England have noticed demand in mid-March coming in below expectations for the period, but other grid operators are monitoring for potential impacts as cities and states continue to take increasing measures to curb the spread of COVID-19. European power grids showed declines in demand in certain countries such as Italy, which implemented a lockdown in early March.

MISO has observed some load reductions. While load is weather dependent, MISO's peak for March to-date is down 18% compared to March 2019 and is down 13% month-to-date compared to the March average since 2014, spokesperson Allison Bermudez said in an email March 23.

"We believe this is attributed to a combination of both the milder weather and the pandemic-related closures and adjusted operating hours of non-critical businesses," Bermudez said. MISO operators are also experiencing a smoother morning ramp as people stay at and work from home.

"We expect the peak hour of the day could shift forward an hour to between 10 a.m. and 11 a.m.," Bermudez said.

READ MORE: Sign up for our weekly coronavirus newsletter here, and read our latest coverage on the crisis here.

PJM Interconnection Senior Vice President of Operations Michael Bryson compared the dip in load during the midweek March 17-19 period to what would happen on a snow day, when schools and some businesses close. "The impact so far has been noticeable, but not severe," Bryson said in a March 23 post on PJM's Inside Lines blog.

"On Monday, March 16, for example, PJM would normally have expected about 100,000 MW of load. With the special circumstances caused by coronavirus restrictions, the forecast was lowered to about 94,500 MW, and it came in at about 95,500 MW," PJM said. The grid operator also noticed the morning peak March 17 arriving one to two hours later than its forecast predicted. The evening peak that day was also about 5% lower than expected, PJM said.

The New York ISO is not observing major changes to peak demand. New York has the highest number of COVID-19 cases in the nation, with 20,875 reported by Gov. Andrew Cuomo's office March 23.

"We are not currently seeing a significant decrease in daily peak demand, but we are observing shifts in energy usage patterns throughout the state compared to prior weeks. We will continue to monitor for trends as new data becomes available," NYISO spokesperson Zack Hutchins said in an email.

Similar reports were coming out of New England, where social distancing and shuttered businesses are beginning to show up in the data.

With residents and businesses across New England changing their behavior in response to the COVID-19 pandemic, ISO New England is seeing a decline in system demand of approximately 3% to 5% compared to what would normally be expected under weather conditions in the region, spokesperson Matt Kakley said.

"In addition to overall declines in consumer demand, these societal changes are also affecting demand patterns across the region," Kakley said. "Our forecasters are seeing load patterns that resemble those of snow days, when schools are closed and many are home during the day." These patterns include a slower-than-normal ramp of usage in the morning and increased energy use in the afternoon. Though the pandemic is affecting energy usage, weather conditions remain the primary drivers of system demand, Kakley said, adding that the region's power system continues to remain reliable.

In the Southwest U.S., COVID-19 impacts are not yet significantly showing up in the data.

The Electric Reliability Council Of Texas Inc. and the Southwest Power Pool are monitoring electric load patterns but have not reported any difference in load to-date, representatives said.

Weather, shelter-in-place orders affect California

Given California's broad geographic area and wide-ranging weather, a mixture of impacts is being observed.

"Colder than average temperatures and weather systems moving through are adding to the challenges of isolating the effects of the coronavirus on consumption," California ISO spokesperson Anne Gonzales said. Since shelter-in-place policies have started rolling out, there has been a mix of cloud cover and partly sunny days across the state. The alternating sunshine and cloud cover affects rooftop solar production, which makes forecasting load more challenging, Gonzales said.

"In the areas currently under shelter-in-place directives and orders, we are seeing reduction in load, especially in those that are heavily residential. Inland areas with more industrial activity are not seeing the level of load reduction, but they are also not in shelter-in-place areas," Gonzales said.

While CAISO is seeing lower consumption needs, it is still analyzing how much of a reduction there is and running models to isolate for shelter-in-place behavior.

"Once we get several days of shelter-in-place and one weekend under our belt, we will be able to see more defined patterns in the behavioral changes that are occurring affecting energy consumption," Gonzales said.

"We are collaborating and sharing information with other [independent system operators] and [regional transmission organizations] across the U.S., and globally, including Italy and France, to get perspective from other grids that are dealing with impacts of the COVID-19 virus," Gonzales said.

Similar impacts in Canada

In Canada, the Alberta Electric System Operator's load from March 16-23 fell by 266 MW on average, or 2.6%, compared to levels expected without the impact of COVID-19. "On an hourly basis, we are seeing a lower ramp up in the morning (5-8 am) compared to conditions before COVID-19 started impacting Alberta," AESO spokesperson Tara De Weerd said in an email.

With many businesses shut, Independent Electricity System Operator spokesman John Cannella said demand in Ontario has been about 300 MW less than usual as of March 24. The difference is equivalent to the peak demand of the town of Oakville, Ontario, about 25 miles southwest of Toronto. Similar to other grid operators, the IESO has noticed morning peak usage shift later with fewer people commuting.

"The evening electricity peak has flattened," Cannella said. "Normally there is an increase around 5-6 p.m. as people return home from work and begin using electricity. Instead, demand now remains the same during this time as people are already at home. Looking ahead, we can expect further demand reductions as more businesses, including industry, temporarily shut down."

Jared Anderson is a reporter for S&P Global Platts. S&P Global Market Intelligence and S&P Global Platts are owned by S&P Global Inc.