News Detail

Electricity Reliability During Summer Months in California

  • Possibility of electricity shortages this summer
  • Informational resources for City of Palo Alto Utilities (CPAU) customers
  • Palo Alto's situation
  • California's electricity delivery system is strained
  • California's Stage I Emergency
  • Stage II Emergency
  • State III Emergency
  • Rotating outages

Possibility of electricity shortages this summer
The California Energy Commission and Independent System Operator have predicted a much lower chance of power shortages this year than last. There are measures, however, that we can implement together to reduce the possibility of outages. The alternative is to risk a citywide disconnection from the transmission system if we are unable to provide sufficient load reduction in Palo Alto. Clearly this is a scenario we all wish to avoid. If a state power shortage occurs, all electric utilities, including the CPAU, are required to meet California central grid curtailment requests. The worst case scenario could mean involuntary rolling localized blackouts for Palo Alto businesses and residents that last up to a few hours.

Informational resources for CPAU customers

  • Electric Reliability Information Line at 650-306-8107 for updates on the California and Palo Alto electric supply situation
  • Energy savings tips and electric use reduction ideas
  • State's FlexYourPowerSM information
  • Automated power outage reporting system at 650-496-6914 provides a recording of areas impacted
  • Customer Service Center at 650-329-2161 from 8:00 am until 5:00 pm, Mondays through Fridays
  • Independent System Operator's state curtailment plans and shortage alerts at
  • Current weather and electricity capacity conditions at System Conditions

We will keep you informed about this issue and its impacts on Palo Alto as the summer progresses. 

Palo Alto's situation
The CPAU, through its electric supply contracts and partnership in the Northern California Power Agency, has sufficient generating capacity to fully meet the Palo Alto's electrical needs. Delivery from the supply sources to the City border, however, is made through the statewide, interconnected transmission system. Due to circumstances beyond CPAU's control, events affecting this system can impact Palo Alto electric customers. 

California's electricity delivery system is strained
The State’s electricity system is in delicate balance. If there is insufficient electricity on a statewide basis to meet demand, or if there is greater demand in one geographic area than existing transmission lines are able to meet, then the entire interconnected delivery system, or "grid", will be affected. This situation is due to a variety of factors:

  • Insufficient generating capacity (making power)
  • Insufficient transmission line capability (moving power)
  • High temperatures leading to increased air conditioning
  • Significant load growth within the state due to the booming economy

The only choices available to the operators of the system are to find additional capacity or to reduce the "load", or demand, for electric power. This demand reduction can be achieved in a variety of ways such as turning off unneeded equipment and lights, to lower thermostat settings or activating emergency generators. For ideas of how to reduce electric use, click here.

The not-for-profit California Independent System Operator (Cal-ISO) is chartered to manage the bulk of California's transmission system. They balance the available supply of electricity from generators inside and outside the state, with the demand from users. When demand exceeds supply, or demand exceeds the ability of the transmission system to move sufficient energy to meet demand, the Cal-ISO takes steps to return the system to equilibrium. These steps can include day-ahead "Warnings" or "Alerts", or same-day declarations of various "Stages of Emergency."

A 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 unneeded consumption.

A 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 will be asked to do so. Palo Alto does not have such customer contracts, so customer action when notified will be purely voluntary when they are notified of the first two Stages.

A Stage Three Emergency is initiated when generation reserves fall below one-and-a-half percent and will probably result in "rolling blackouts" among large "blocks" of electric utility customers throughout California, including Palo Alto. We will inform you as Cal-ISO notifications are made and request that you voluntarily reduce your electric demand to the greatest extent possible. We urge you to review or update your Emergency Plans, test emergency equipment, install Uninterruptible Power Supplies (UPS's) for your data processing equipment, and review fuel supply contracts for your emergency generators. If you are a large electricity user and do not have emergency or back-up generation on site for your critical loads, the CPAU can arrange for free technical assistance in evaluating your options. Contact Utility Marketing Services at 650-329-2241 for information.

Rotating outage blocks for CPAU customers
We have divided the City's total electric load into 20 blocks in order to shed large amounts of load should it become necessary to protect the integrity of the electric system and to meet our obligations as an electric utility. This will only be done as an emergency measure and there may not be time to provide advance warning prior to implementation. We anticipate that no single block will be without power for more than two hours.

During all power outages, whether rolling blackouts or other unplanned outages, Palo Altans can call 650-496-6914 for information about areas currently impacted.

We will provide ongoing updates about this statewide reliability issue to CPAU customers throughout the summer. And the CPAU remains committed to providing its customers with the finest service possible and appreciate your assistance.


Last Updated: February 6, 2007