IOU · South Dakota · EIA 13809

NorthWestern Energy - (SD)

IOU · South Dakota · 65K customers. According to the U.S. Energy Information Administration's EIA Form 861, reliability for 2023 shows SAIDI 117 minutes/customer.

Reliability detail ↓ South Dakota utilities

Reliability verdict

NorthWestern Energy - (SD) shows above-average chronic reliability in 2023: 74 minutes SAIDI excluding major events across 65K customers.

117 min
SAIDI 2023
1.37
SAIFI 2023
74 min
SAIDI ex-MED
65K
Customers

Chronic reliability judged on SAIDI excluding major event days when reported (IEEE 1366). Source: EIA Form 861 · August 2026.

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Signature read: mid-cohort SAIDI between the 96 and 258 minute tercile cuts.

What mid-pack NorthWestern Energy - (SD) filings show

NorthWestern Energy - (SD) is an 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. Investor ownership puts this utility under the regulatory authority of the state public utility commission, which reviews its rate requests and reliability record.

In 2023, the average NorthWestern Energy - (SD) customer experienced 116.5 minutes of power interruptions, the industry-standard SAIDI metric (System Average Interruption Duration Index). That is comfortably under the 120–180 minute national benchmark range, a sign of solid grid resilience and quick outage response. Over the same period, SAIFI (outage events per customer) was 1.37, putting the typical customer at 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 dropped from 159.0 to 116.5 minutes across that span, a direction regulators and prospective customers tend to watch closely.

C
Reliability Score
58/100
NorthWestern Energy - (SD) · 3 of 3 dimensions reported

Based on this utility's own EIA Form 861 reliability record -- baseline (major-event- excluded) outage duration, total outage duration, and outage frequency -- each benchmarked against every reporting utility nationwide. Not a measure of electricity rates or customer service, which this portal does not track.

Baseline Reliability C+ 73.9 min/yr
SAIDI excluding major-event days — day-to-day grid performance
Total Outage Duration C+ 116.5 min/yr
SAIDI including storms and major events — the full-year experience
Outage Frequency D 1.37/yr
SAIFI — average number of interruptions per customer per year
SAIDI vs. national mean (341 min) 15.5%

117 min/year per customer

NorthWestern Energy - (SD) SAIDI

Power-out minutes per year (2023)

117 SAIDI117 SAIDINat. avg 341341SAIDI117SAIDI

Excellent

SAIDI by year (2020-2023)

Minutes per customer-year · EIA Form 861

Year-by-year SAIDI for NorthWestern Energy - (SD) from the same EIA filings as the table below. Lower is better; major-event years can spike the headline figure.

Source: U.S. EIA Form 861 As of August 2026

NorthWestern Energy - (SD) SAIDI trend

0 30 60 90 120 150 180 2020 2021 2022 2023 159 91.3 127.8 116.5
Year-by-year SAIDI from the same EIA filings as the table below. Lower is better; major-event years can spike the headline figure.

NorthWestern Energy - (SD) vs the nationwide SAIDI distribution

Where this utility's headline SAIDI sits among every EIA Form 861 utility with a reported figure

117 Lower than most fewer outage minutes than 61% of 911 utilities

Utilities nationwide, banded by latest reported SAIDI (minutes)

Each bar is a band; taller bars hold more utilities. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.

Source U.S. EIA Form 861 reliability filings · August 2026

Price vs. reliability

Where NorthWestern Energy - (SD) sits on price vs. reliability

Among the 781 U.S. utilities large enough to report both revenue per customer and a recent outage record, NorthWestern Energy - (SD) charges more per customer than 60% of them, and is more reliable (lower SAIDI) than 65% of them, placing it in the quadrant where it pays more and is more reliable. Revenue per customer and outage minutes are independent figures: paying more does not guarantee fewer outages.

NorthWestern Energy - (SD) vs. a 40-utility national peer sample, price percentile vs. reliability percentile. Scatter plot of 41 data points (bubble-sized by third dimension). 050100150 050100150 Best valuePays for itCheap + riskyWorst deal Price percentile Reliability percentile Point, Price percentile: 0 · Reliability percentile: 30Point, Price percentile: 3 · Reliability percentile: 40Point, Price percentile: 5 · Reliability percentile: 32Point, Price percentile: 8 · Reliability percentile: 80Point, Price percentile: 10 · Reliability percentile: 45Point, Price percentile: 13 · Reliability percentile: 87Point, Price percentile: 15 · Reliability percentile: 12Point, Price percentile: 18 · Reliability percentile: 25Point, Price percentile: 20 · Reliability percentile: 17Point, Price percentile: 23 · Reliability percentile: 77Point, Price percentile: 25 · Reliability percentile: 10Point, Price percentile: 28 · Reliability percentile: 50Point, Price percentile: 30 · Reliability percentile: 60Point, Price percentile: 33 · Reliability percentile: 57Point, Price percentile: 35 · Reliability percentile: 7Point, Price percentile: 38 · Reliability percentile: 0Point, Price percentile: 40 · Reliability percentile: 72Point, Price percentile: 43 · Reliability percentile: 2Point, Price percentile: 45 · Reliability percentile: 20Point, Price percentile: 48 · Reliability percentile: 15Point, Price percentile: 50 · Reliability percentile: 43Point, Price percentile: 53 · Reliability percentile: 37Point, Price percentile: 55 · Reliability percentile: 97Point, Price percentile: 57 · Reliability percentile: 100Point, Price percentile: 60 · Reliability percentile: 5Point, Price percentile: 65 · Reliability percentile: 70Point, Price percentile: 68 · Reliability percentile: 92Point, Price percentile: 70 · Reliability percentile: 75Point, Price percentile: 73 · Reliability percentile: 52Point, Price percentile: 75 · Reliability percentile: 47Point, Price percentile: 78 · Reliability percentile: 90Point, Price percentile: 80 · Reliability percentile: 22Point, Price percentile: 83 · Reliability percentile: 95Point, Price percentile: 85 · Reliability percentile: 35Point, Price percentile: 88 · Reliability percentile: 27Point, Price percentile: 90 · Reliability percentile: 82Point, Price percentile: 93 · Reliability percentile: 65Point, Price percentile: 95 · Reliability percentile: 85Point, Price percentile: 98 · Reliability percentile: 67Point, Price percentile: 100 · Reliability percentile: 55NorthWestern Energy - (SD), Price percentile: 60 · Reliability percentile: 65
NorthWestern Energy - (SD) vs. a 40-utility national peer sample, price percentile vs. reliability percentile.

Revenue per customer: $2,688/year · Latest SAIDI: 116.5 minutes/year.

SAIDI 2023 breakdown: 116.5 minutes

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. Excluding major storm impacts, this beats the national average, a sign of above-average reliability.

What type of utility is NorthWestern Energy - (SD)?

NorthWestern Energy - (SD) is classified as a IOU serving South Dakota.

How many customers does NorthWestern Energy - (SD) serve?

NorthWestern Energy - (SD) serves approximately 64,654 customers in South Dakota.

How has NorthWestern Energy - (SD)'s reliability changed over time?

NorthWestern Energy - (SD) has 4 years of reliability data (2020-2023). This utility's SAIDI has stayed fairly flat over the period. Review the trend table above for year-by-year detail.

Utility Profile

Type
IOU
State
South Dakota
Customers
64,654
Annual Revenue
$0.17B
EIA ID
13809

Explore

Utilities with similar EIA profiles

Two cross-state peer sets for NorthWestern Energy - (SD). Same-state SAIDI neighbors stay in Read-with below; these neighborhoods are nearest other-state utilities with at least 10,000 reported customers.

Similar customer count

Nearest utilities by Form 861 customers (65K here), outside South Dakota.

Unitil Energy Systems 64K · NH Laurens Electric Coop, Inc 64K · SC Central Georgia El Member Corp 66K · GA Lumbee River Elec Member Corp 66K · NC

Similar chronic SAIDI

Nearest utilities by latest SAIDI minutes (116.5 here), outside South Dakota, excluding the customer-peer set.

Empire Electric Assn, Inc 116.4 min · CO Albany Utility Board 116.3 min · GA Southern California Edison Co 115.9 min · CA Polk-Burnett Electric Coop 117.4 min · WI

Source: U.S. Energy Information Administration Form 861 annual electric power industry survey · ZIP service territory: OpenEI. Disclaimer: informational only, not professional advice. See full disclaimer · methodology.