# SAIDI

The System Average Interruption Duration Index (SAIDI)[1] is commonly used as a reliability indicator 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, and according to IEEE Standard 1366-1998 the median value for North American utilities is approximately 1.50 hours.

## Comparison of SAIDI by country

The following is a table of SAIDI for different countries; the share of renewable energy (gross electricity consumption) is also given:[2]

Country Population

(million)

SAIDI

(minutes)

Renewable energy

share (%)

Year

(2013 if not named)

USA 328 280 23 2019[3][4]
Luxembourg 0.5 10 5.8
Denmark 5.6 11.25 43.1
Switzerland 8.1 15 19
Germany 83.2 12.2 49.3 2020[5][6]
Netherlands 16.8 23 10
Austria 8.5 33.96 68
Belgium 11.2 34.75 with major e. 12.4
Italy 59.8 42.27 31.3
Great Britain 64.1 54.71 13.8
Spain 46.6 58.2 36.7 2011
Slovenia* 2.1 60 33.1
France 63.9 68.1 16.8
Hungary 9.9 67.21 6.6
Sweden 9.6 70.77 61.8
Lithuania 3 72.67 13.1
Ireland 4.6 82 20.8 2010
Portugal 10.5 88.7 49.1
Greece 11.1 96 21.2
Czechia 10.5 98.01 12.8
Slovakia 5.4 110.9 20.8
Finland** 5.4 138 with major e. 30.9
Norway* 5.1 144 with major e. 37.4
Cyprus 1.1 148 6.6 2012
Croatia 4.3 176.1 42.2
Poland 38.5 254.9 10.7
Malta* 0.4 360 1.6
Estonia 1.3 378.5 with major e. 13
Latvia 2 621 48.8
Romania 21.3 635 37.5 2009

*, ** = Alternative SAIDI (e.g. T-SAIDI)