Reliability of U.S. Electric Utilities

Reliable electric power is central to the safety and sustainability of our communities. Power outages disrupt many elements of our lives. Outages happen to the power system for a variety of reasons, from accidents and aging equipment to inclement weather. Since electric power plays a critical role in our lives, freedom from these outages is critical, and utilities work hard to minimize their frequency and length. The system average interruption duration (SAIDI) and frequency (SAIFI) indices describe the way users experience these outages. These reliability indices detail the electric service reliability at the distribution level. They are the basis for many reliability goals and benchmark performance against peer utilities. Moreover, they can help a utility and the public track the tangible benefits of their investments.

Several bodies, including the U.S. Energy Information Administration (EIA) and the Institute of Electrical and Electronics Engineers (IEEE), develop and publish reliability indices such as SAIDI and SAIFI annually. To improve the usefulness of these data, this white paper details some of the recent work undertaken to understand the drivers of utility reliability.