# SAIDI

The System Average Interruption Duration Index (SAIDI)[1] is commonly used as a reliability index by electric power utilities. SAIDI is the average outage duration for each customer served, and is calculated as:

${\displaystyle {\mbox{SAIDI}}={\frac {\sum {U_{i}N_{i}}}{N_{T}}}}$

where ${\displaystyle N_{i}}$ is the number of customers and ${\displaystyle U_{i}}$ is the annual outage time for location ${\displaystyle i}$, and ${\displaystyle N_{T}}$ is the total number of customers served. In other words,

${\displaystyle {\mbox{SAIDI}}={\frac {\mbox{sum of all customer interruption durations}}{\mbox{total number of customers served}}}}$

SAIDI is measured in units of time, often minutes or hours; it is usually measured over the course of a year. According to IEEE Standard 1366-1998, the median value for North American utilities is approximately 1.50 hours. According to the U.S. Energy Information Administration Annual Electric Power Industry Report, it is 2.0 hours, rising to the range of 3.5 to 8 hours, when "major events" are included.[2]

## Comparison of SAIDI by country

The following is a table of SAIDI for different countries, calculated using the methodology in the World Bank's Doing Business 2016-2020 studies:

Country Population

(million) in 2020[3]

SAIDI

(hours) in 2019[4]

SAIDI

(hours) in 2020[5]

Austria 8.9 0.7 0.6
Belgium 11.5 0.7 0.4
Croatia 4.0 4.8 3.3
Cyprus 1.2 0.3 0.6
Czechia 10.7 0.5 0.5
Denmark 5.8 0.5 0.5
Estonia 1.3 0.3 0.3
Finland 5.5 0.6 0.2
France 67.6 0.2 0.4
Germany 83.2 0.2 0.3
Greece 10.7 1.9 1.6
Hungary 9.8 2.8 2.6
Ireland 5.0 0.3 0.8
Italy 59.4 0.5 1.3
Latvia 1.9 1.0 1.0
Lithuania 2.8 0.4 0.4
Luxembourg 0.6 0.4 0.4
Malta 0.5 0.6 0.8
Netherlands 17.4 0.8 0.8
Norway 5.4 0.7 1.5
Poland 37.9 1.3 1.1
Portugal 10.3 0.6 0.5
Romania 19.3 2.1 3.1
Slovakia 5.5 1.0 0.9
Slovenia 2.1 0.6 0.1
Spain 47.4 0.5 0.5
Sweden 10.4 0.6 0.6
Switzerland 8.6 0.2 0.2
United Kingdom 67.1 0.3 0.3
United States 331.5 1.2 1.3

## References

1. ^ Yeddanapudi, Sree. "Distribution System Reliability Evaluation". Iowa State University. Archived from the original on 26 December 2011. Retrieved 18 June 2011.
2. ^ "U.S. electricity customers averaged seven hours of power interruptions in 2021", (published November 14, 2022), Average duration of total annual electric power interruptions, United States (2013--2021)) hours per customer.
3. ^ The World Bank, Data Bank "World Development Indicators", total population 2020, https://databank.worldbank.org/reports.aspx?source=2&series=SP.POP.TOTL&country=
4. ^ The World Bank, Data Bank "Doing Business", SAIDI index WB 2019, https://databank.worldbank.org/SAIDI-Index-WB/id/dd1d6036
5. ^ The World Bank, Data Bank "Doing Business", SAIDI index WB 2020, https://databank.worldbank.org/SAIDI-Index-WB/id/dd1d6036