Why Do Power Outages Happen?

There are two main reasons that power outages occur: 1) as a result of damage to or failure of some part of the electrical system; 2) as a preventative measure to protect life and safety.

Outages Caused By Damage

Outages can happen as a result of damage to equipment or failure of markets involved in the generation, transmission, or distribution of electricity from remote locations to where it is used. Outages can also occur due to problems on a customer’s own property.

  1. Customer Property - Damage to the wires bringing electricity to a customer’s property from the grid (“service drop”) due to contact with a tree branch is one potential source of an outage. Damage to equipment that is confined a customer’s property only affects the power to that customer.
  2. Distribution - Distribution refers to the portion of the electric grid that directly provides power to your home. Distribution lines are generally what you see in front of your house on a pole. Damage to distribution lines generally impacts a smaller area and fewer people than damage to transmission lines. Damages to distribution lines may be caused by errant drivers, stray balloons, or animals, or malfunctioning equipment.
  3. Transmission -Transmission lines move electricity generated in a distant location to locations closer to where people live. Damage to transmission lines tend to create disruptions across larger geographic areas than damage to distribution or customer equipment and can threaten grid stability if not properly managed.
  4. Generation - On very rare occasions, there may not be enough electricity offered to meet everyone’s anticipated needs. The causes of this type of outage can vary and be difficult to assess, but may include extreme deviations from historical weather conditions, market manipulation, and fuel supply problems, among others. Without appropriate management, this type of outage could have serious consequences for grid stability.

Outages To Protect Safety

Electricity is inherently dangerous. As little as 100 milliamps of electrical current can be lethal to human beings. Climate and weather conditions, together with land use and resource management decisions, have increased the probability of wildfires starting for any reason and have worsened the consequences of fires that do start.  Shutting off power is a long and widely practiced method of protecting people and property from electrical risks. Utilities are applying this method in new ways to reduce wildfire risk, subject to oversight by CPUC. Over time, CPUC expects utilities’ investments in other methods of wildfire mitigation to eliminate the need to rely on shutting off the power. Below are examples of outages that are intended to protect safety:

  1. Tripped Circuit Breaker - Circuit breakers are protective devices required by the National Electric Code and local building ordinances that shut off power when they detect a problem to prevent electrocution or fire.
  2. Fire Safety Settings on Protective Equipment - Utilities install protective equipment on their distribution and transmission lines that are very similar to circuit breakers in homes. These shut off power in the event of a problem to prevent electrocution or fire. Unlike the circuit breakers in homes, the sensitivity of utility equipment can be adjusted. Utilities apply more sensitive settings in areas more prone to fire during riskier conditions. These more sensitive settings can quickly cut power to a line to prevent a spark which could cause a wildfire.
  3. Public Safety Power Shutoffs - Due to increased risks and impacts of wildfire ignitions under certain weather and landscape conditions, utilities may initiate a public safety power shutoff (PSPS) on transmission and/or distribution lines. These areas impact High Fire Threat districts as well as can impact neighboring areas depending on the risk of fire for that geographic area.
  4. Planned Work - Utilities may temporarily shut off the power in certain areas in order to perform planned maintenance or construction work safely, or to facilitate work by others.
  5. Rotating Outages - To avoid the catastrophic outcome of the grid become destabilized in the event of insufficient generation, CPUC requires utilities to develop and maintain an active plan for shutting off the power to different small areas of customers for short periods of time. 

Is a Power Outage Likely Where I Live or Work?

Disasters can strike at any time, anywhere, without warning. The California Governor’s Office of Emergency Services (Cal OES) encourages all Californians to take simple steps to prepare for emergencies in their homes, businesses, and communities.  Although power outages are still rare in California, the risk of an outage in certain areas has increased in recent years. There are several resources available for determining your exposure to different types of power outages:

  1. Distribution (overall reliability) – You can review the IOUs annual electric reliability reports to determine if you live in an area that has historically lower than average reliability. You can also request reliability information directly from your utility. See this page for more information: Electric System Reliability Annual Reports (ca.gov)
  2. Areas where fire safety settings may be activated – In general, utilities are more likely to activate fire safety settings in areas designated as Tier 2 or Tier 3 on the HFTD map during conditions that are more likely to lead to a catastrophic fire.
  3. Areas more subject to PSPS events – Areas of elevated fire risk shown on the HFTD map are more likely to be subject to PSPS events, although PSPS events can be called anywhere.
  4. Generation & Transmission – You can use the website or app of the California Independent System Operator to alert you to any current or potential issues with the bulk generation and transmission system: CAISO outlook

How Can I Prepare for a Power Outage?

Individual, family, and community preparedness is important during disasters. An outage may cause minor inconveniences, but it can also cause major disruptions, such as having no power for your essential medical equipment or accessibility devices.

  1. Cal OES Information Resources - CalOES has a collection of documents, links and videos, all in one place to help make it easier for you to get prepared for when - not if - the next emergency will occur
    1. Cal OES Preparedness Advice for Individuals and Families
    2. Cal OES Power Outage Preparedness Page
  2. Utility Programs – Electric utilities under CPUC jurisdiction offer a variety of programs to provide customers with access to backup power and other support.
    1. Backup generator programs
      1. PG&E – Using backup power
      2. SCE – Customer Resources & Support (sce.com)
      3. SDG&E – Generator Assistance Program and Whole House Generator Program | San Diego Gas & Electric (sdge.com)
      4. PacifiCorp – Backup electric power
    2. Self-Generation Incentive Program (SGIP) - Participating in Self-Generation Incentive Program (SGIP) (ca.gov)
    3. Low Income Energy Assistance Program (LIHEAP) - LIHEAP is a federally funded assistance program overseen by the California Department of Community Services and Development (CSD) and administered by 31 Action Agencies throughout California. LIHEAP may also prioritize applicants based on the greatest need and income, as well as households with vulnerable populations, including the elderly, disabled and households with young children. LIHEAP offers the following types of assistance:

The Power Is Out - Where Do I Find Out What’s Going On?

    1. Distribution
      1. PG&E System Outage Center
      2. SCE Outage Center
      3. SDG&E Outage Center
      4. PacifiCorp Outage Center
      5. Liberty Outage Center
      6. BVES Outages News & Outage Safety
    2. PSPS
      1. PG&E PSPS Outage Map
      2. SCE PSPS Outage Map
      3. SDG&E PSPS Outage Map
      4. PacifiCorp PSPS Outage Map
      5. Liberty PSPS Outage Map
      6. BVES PSPS Outage Page
    3. Generation & Transmission – CAISO Outlook

Who Restores Electricity?

Your utility will restore electricity to your residence. It assesses the site for any electric hazard, repairs any damage, then restores power per CPUC rules.  Disaster areas can still be dangerous after the hazard passes, so utility crews follow the guidance of local public safety officials before entering an area that has been impacted by disasters.

For larger scale disasters that involve local, county or state emergency management organizations, the CPUC requires investor-owned electric utilities to coordinate and support local, county and state governments on issues related to power restoration and supplying temporary power to critical facilities.

ADDITIONAL RESOURCES