Frequently Asked Questions
Common questions about electric utility reliability metrics and how to use PlainUtility.
What is SAIDI and why does it matter?
SAIDI stands for System Average Interruption Duration Index. It measures the average total minutes per year that a typical customer is without power. A lower SAIDI means fewer total minutes of outages. For example, a SAIDI of 120 means the average customer experienced 2 hours of total power outage time over the year. It is the most widely used measure for comparing utility reliability.
What is SAIFI?
SAIFI stands for System Average Interruption Frequency Index. It measures how many times per year the average customer experiences a power interruption. A SAIFI of 1.5 means the average customer had 1.5 outage events in a year. Combined with SAIDI, it helps you understand whether outages are frequent but short (high SAIFI, moderate SAIDI) or infrequent but long (low SAIFI, high SAIDI).
What is the difference between 'with MED' and 'without MED' reliability?
MED stands for Major Event Day — typically a large storm or catastrophic event. 'With MED' includes all outages including storms, giving the full customer experience. 'Without MED' (nMED) excludes major events to show day-to-day infrastructure reliability. Both are published by utilities to the EIA and serve different analytical purposes.
Where does PlainUtility get its data?
Reliability data (SAIDI, SAIFI) comes from the U.S. Energy Information Administration Form 861 Annual Electric Power Industry Report — the federal survey of all US electric utilities. ZIP code to utility mappings come from OpenEI's Utility Rate Database (URDB) service territory files.
Why is my utility not listed?
Not all utilities report reliability data to the EIA. Smaller municipal utilities and some cooperatives may be exempt from reporting requirements or may not participate voluntarily. The database covers approximately 900+ utilities that submitted Form 861 reliability data.
Can I look up reliability by ZIP code?
Yes. PlainUtility uses OpenEI service territory data to map ZIP codes to their serving utility, then shows that utility's reliability metrics. Some ZIP codes are served by multiple utilities, in which case you may see more than one result.
How do I compare my utility to state or national averages?
Each utility page shows SAIDI and SAIFI values alongside state averages for context. The state pages show aggregated reliability statistics for all utilities in each state. National comparisons are available on the rankings pages.
How current is the data?
Current data covers 2020–2023. The EIA publishes updated Form 861 reliability data annually, typically 12–18 months after the survey year. We update our database when new annual data becomes available.