The System Average Interruption Duration Index (SAIDI) measures the average number of minutes an average customer was without power in a year. We achieved an overall SAIDI of 78.49 in 2011, beating our target of 86.20. This means that, on average, customers in our eight-state region had electric power 99.9 percent of the time last year.
The Customer Average Interruption Index (CAIDI) measures the length of the average power outage in a year.
The System Average Interruption Frequency Index (SAIFI) measures the average number of power outages that an average customer experienced in a year.
We published our first corporate responsibility report (formerly known as the Triple Bottom Line report) in April 2005, with the contents covering the 2004 calendar year, and we have published a similar report in each following year. Our report is based on Global Reporting Initiative (GRI) G3 Sustainability Reporting Guidelines, the most widely used sustainability reporting framework in the world. Additionally, we incorporate the GRI’s Electric Utilities Sector Supplement indicators wherever possible.