With more than 32,000 megawatts (MW) of capacity expected to be available this summer, electricity supplies should be sufficient to meet New England consumer demand, but tight system conditions could develop if forecasted extreme peak conditions occur.
Over 1,600 MW of new generating capacity are expected to be available this summer, including two new natural-gas-fired power plants and one new dual-fuel plant that total about 1,490 MW of capacity acquired through the Forward Capacity Market. In addition, five new grid-scale solar facilities are expected to add nameplate capability of about 90 MW, and two new wind farms will add about 50 MW of nameplate capability. (“Nameplate” refers to the maximum energy a resource could produce if it was operating at its maximum capability.)
ISO New England has well-established operating procedures to maintain grid reliability 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 reserves, and asking businesses and residents to voluntarily conserve energy.
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.