SAIDI
117 min per year
Average outage minutes (2023)
What This Utility Data Tells You
NorthWestern Energy - (SD) is a investor-owned utility operating in South Dakota under EIA identifier 13809. It reports service to approximately 64,654 customer accounts and generated about $0.17 billion in annual electric revenue. As an investor-owned utility, it operates under state public utility commission oversight that reviews rate cases and reliability performance.
In 2023, the average NorthWestern Energy - (SD) customer experienced 116.5 minutes of power interruptions — a metric called SAIDI (System Average Interruption Duration Index). That sits within the 120–180 minute national benchmark range, indicating performance typical of U.S. distribution utilities. SAIFI — the average number of outage events per customer — was 1.37 for the same period, so customers statistically faced roughly 1 distinct interruption that year. Excluding major event days (hurricanes, ice storms), SAIDI drops to 73.9 minutes — the gap between that figure and the headline 116.5 reveals how much weather, not day-to-day infrastructure, drove outages.
The EIA dataset includes 4 years of continuous reporting (2020–2023) for NorthWestern Energy - (SD), which lets you see whether reliability is trending up or down rather than judging from a single snapshot. SAIDI has improved from 159.0 to 116.5 minutes over that window — a meaningful direction for prospective customers and regulators watching capital investment outcomes. All figures on this page come directly from EIA Form 861, the federal annual electric power industry survey — you can cross-reference them with your own utility bill or use them when comparing providers before relocating.
SAIFI
1.37 interruptions/yr
Outage frequency (2023)
Customers
64,654
Served in South Dakota
SAIDI vs. National Average (180 min) 29.1%
117 minutes per customer per year
Minutes without power per year (2023)
Reliability Trend (2020–2023)
| Year | SAIDI (min) | SAIDI nMED | SAIFI | Customers |
|---|---|---|---|---|
| 2020 | 159.0 | 112.6 | 1.543 | 58,953 |
| 2021 | 91.3 | 81.4 | 0.954 | 57,129 |
| 2022 | 127.8 | 79.6 | 1.264 | 62,989 |
| 2023 | 116.5 | 73.9 | 1.367 | 63,238 |
SAIDI nMED = SAIDI without major event days. Source: EIA Form 861.
Frequently Asked Questions
How reliable is NorthWestern Energy - (SD)?
NorthWestern Energy - (SD) had a SAIDI of 116.5 minutes in 2023, meaning the average customer experienced about 117 minutes of outages that year. This is near the national average.
What type of utility is NorthWestern Energy - (SD)?
NorthWestern Energy - (SD) is classified as a IOU serving South Dakota. Investor-owned utilities (IOUs) are for-profit companies regulated by state public utility commissions.
What does SAIDI mean for NorthWestern Energy - (SD)?
SAIDI (System Average Interruption Duration Index) measures the average total minutes per year that a customer of NorthWestern Energy - (SD) experiences power outages. A lower SAIDI indicates better reliability. The national average is roughly 120-180 minutes per year, so comparing NorthWestern Energy - (SD)'s SAIDI to that benchmark shows whether this utility is above or below average.
How many customers does NorthWestern Energy - (SD) serve?
NorthWestern Energy - (SD) serves approximately 64,654 customers in South Dakota. Customer count can affect reliability metrics because larger utilities may face different infrastructure challenges compared to smaller ones.
How has NorthWestern Energy - (SD)'s reliability changed over time?
NorthWestern Energy - (SD) has 4 years of reliability data (2020-2023). SAIDI has remained relatively stable over this period. Review the trend table above for year-by-year detail.
What is SAIDI without major event days?
SAIDI "without major event days" (SAIDI nMED) excludes outages caused by hurricanes, ice storms, and other catastrophic weather events. It better reflects day-to-day infrastructure reliability rather than vulnerability to extreme weather. Both standard SAIDI and SAIDI nMED are shown in the reliability trend table above.
Utility Profile
- Type
- IOU
- State
- South Dakota
- Customers
- 64,654
- Annual Revenue
- $0.17B
- EIA ID
- 13809
Related Data
Guides
Data Source: U.S. Energy Information Administration Form 861 annual electric power industry survey. ZIP service territory from OpenEI.
Related
Data sourced from official EIA reliability statistics and OpenEI utility rate database. See our methodology for details. Retrieved and formatted by PlainUtility Editorial
Disclaimer: This information is provided for informational purposes only and does not constitute professional advice. Data is sourced from the U.S. Energy Information Administration (EIA) Form 861. Consult a qualified professional before making decisions based on this data.
Read our methodology — how this data is sourced, computed, and verified.