New England is expected to have sufficient resources to meet peak consumer demand for electricity this summer under both typical and extreme weather conditions.
Though New England has more than 3,000 MW of solar PV installed, these systems produce their highest output in the early afternoon hours. The increase of solar power in New England has, in effect, pushed the peak hour of grid demand later in the day, when the sun is lower in the sky and production from solar PV systems is also lower. Rather than peaking during the mid-afternoon, as was customary in the summer before PV installations became more widespread, demand for grid power now peaks in the early evening hours.
Last summer, demand for electricity peaked on August 29, 2018, at 25,899 MW – the region’s highest peak in five years. The all-time record for peak demand was set on August 2, 2006, when demand reached 28,130 MW after a prolonged heat wave. In New England, consumer demand for electricity is highest during the summer because of air conditioning use.
ISO New England has well-established operating procedures to maintain a reliable supply of electricity in the event of an unexpected power plant or transmission line outage, an extended heat wave that results in increased consumer demand, fuel supply issues or emissions limitations that affect the amount of electric generation available, or a combination of these factors. These procedures include importing emergency power from neighboring regions, calling on power system reserves, and asking businesses and residents to voluntarily conserve energy.
Read ISO New England’s summer outlook press release.
ISO New England issues forecasts for electricity supplies and power system conditions ahead of summer, when New Englanders use the most electricity, and winter, when fuel for generators can be constrained. The outlooks take into account many factors that could be boons or challenges to the reliable supply and delivery of electricity, such as weather forecasts, available generation capacity, and possible resource scenarios.
Because of relatively low demand for electricity during these times of the year, the ISO does not release specific seasonal forecasts ahead of spring and fall. Electricity supplies are generally more than sufficient to meet demand, barring extraordinary circumstances. Typical peak demand ranges from 15,000 to 16,900 MW for spring and 15,900 to 17,300 MW for fall, though peaks can be much higher if summer-like weather edges into these seasons.
During periods of mild weather when there’s little need for climate control, the amount of electricity being generated can at times exceed demand, particularly on weekends and during early morning hours. These situations can be dangerous if too much supply leads to excessively high system voltages and frequencies and unscheduled flows of power into neighboring regions.
When generation and external transactions are anticipated to exceed system demand, the ISO first asks generators to voluntarily lower output and then if necessary may order some generators to reduce output or shut down. This process is carefully executed because:
See details on the ISO’s protocol for managing these situations in FAQs: Minimum Generation Emergency.