Energy shortages are declared by Cal-ISO (California Independent System Operator), the nonprofit agency that manages the state electric transmission system. Cal-ISO balances the supply of electricity from generators inside and outside the State, with the demand for electricity from users. Shortages occur when there is not enough power available to support the needs of residents and businesses throughout California. When demand exceeds supply, or demand is more than the transmission system can move from the generators to your utility, Cal-ISO takes steps to keep the system in equilibrium and avoid grid failures. These steps can include day-ahead Warnings, Alerts, or Stages of Emergency.
- Stage One Emergency: Takes effect when electric generation reserves fall below seven percent statewide. The media is alerted and electric consumers are asked to reduce unnecessary consumption.
- Stage Two Emergency: Is declared when reserves drop below five percent. At this level, large commercial customers throughout the State who have contracts to curtail power during high demand are asked to do so. Silicon Valley Power also asks Santa Clara businesses and residents to voluntarily reduce power usage during a Stage Two Emergency.
- Stage Three Emergency: Is initiated when generation reserves fall below one and one-half percent and can result in rolling blackouts among large blocks of electric utility customers throughout California, including Santa Clara.
A Stage Three Emergency alert is serious. If more power
generation is not found and/or customers do not reduce energy use
enough, the entire electric grid could fail. This would affect everyone
regardless of their source of power. Because of this, all utilities
throughout the State are required to reduce their energy load during a
Stage Three Emergency.