Actions to mitigate the 2019 novel coronavirus disease (COVID-19) have caused daily weekday electricity demand in New York City to decrease by 16% in April compared with expected demand, after accounting for seasonal temperature changes. However, decreases in the city’s electricity demand have not occurred uniformly across the day. The largest differences between actual and expected demand have been during daytime weekday hours when many schools and businesses that normally would have been open are now closed.
The U.S. Energy Information Administration’s (EIA) Hourly Electric Grid Monitor provides hourly electricity demand data from the 64 balancing authorities in the contiguous United States and subregional demand for select balancing authorities. The New York Independent System Operator (NYISO) operates the electric grid serving New York state and provides demand for its subregions, including New York City, which is also called NYISO Zone J.
By combining this data with hourly temperature data available from the National Oceanic and Atmospheric Administration, EIA compared the electricity demand of every hour of the day for all weekdays in 2020 through May 1 with the average demand of all instances of the same hour of the day with the same hourly temperature (referred to as temperature-comparable demand) from January through June 2019. Weekends and holidays were excluded.
For New York City, the largest difference in electricity demand in April 2020 compared with 2019 temperature-comparable demand was during weekday mornings from 7:00 a.m. to 11:00 a.m. when electricity demand was 22% lower than expected in those hours. For midday, from 11:00 a.m. to 6:00 p.m., the average percentage decrease was about 20%. The deviation from temperature-comparable demand gradually decreased in the evening hours, down to 10% by midnight.
Overnight differences were lower: from midnight to 4:00 a.m., the deviation from temperature-comparable demand was lowest, averaging about 7%. Changes to demand are less pronounced between midnight and 4:00 a.m. because most people are normally asleep during this time and many nonessential businesses that have been ordered closed as part of COVID-19 mitigation actions are also normally closed during these early morning hours.
The shape of these hourly deviations is consistent with those reported by NYISO. In a recent blog post about current electricity consumption patterns, NYISO observes “that the morning peak arrives later in the day; patterns similar to what we would see during a widespread snow day. This reduction is being driven by reduced demand from commercial consumers, with an increase in residential energy use, especially during the midday.”
The diverging electricity demand patterns became noticeable in March when New York City and New York state began taking steps to limit the spread of COVID-19, including closing schools and implementing a “New York State on PAUSE” order. As each of these mitigation actions were taken, electricity demand in New York City dropped further below temperature-comparable demand.
The hourly data for 2019 in the graphs below show the normal curved pattern in the relationship between electricity demand and temperature: demand increases when temperatures are very cold or very hot and decreases when temperatures are moderate. The graphs also show the relationship of electricity demand and hour of day: demand is typically higher during the daytime than at night. The hourly data for 2020 show the effect of the COVID-19 mitigation actions layered on top of the normal relationships between electricity demand, temperature, and hour of day.