Grid reliability · 2024 · 13 reporting utilities

Power outages in South Dakota

The utilities that reported here serve 365,552 customers between them, not the whole state. Weighted by customer count, they averaged 62 min without power in an ordinary year and 86 min once major events are counted. Each figure comes only from the filers that published it, and the counts are below.

What it means

Why there are two numbers

Across the utilities that filed both figures, major events account for 28% of the outage time South Dakota recorded once they are counted: 86 min against 62 min without them, a factor of 1.4×. Solar panels alone do not help during an outage, because a grid-tied array shuts down when the grid does, so riding through one is a battery question. This figure will not answer it: it is an annual average across a utility’s customers, not the length or the load of any single outage. What it does say is how much of the outage time here arrives with major events rather than on ordinary days.

The comparison is drawn from the 13 utilities that filed both figures, which is all of them, so both sides of the ratio describe the same set of customers. The two headline figures above are averaged over everyone who filed each one, so dividing them would not give this number.

Ordinary year62 min48 of 51 jurisdictions, longest first · 13 filings

With major events86 minStorms, ice, and fires included as filed · 13 filings

Interruptions a year0.7×Ordinary year; 0.8× with major events

The bill sideWhat solar offsetsRates and modelled output by utility

The utilities behind the average

Each of South Dakota’s figures is a customer-weighted average of the filings that carried that metric, not of the table as a whole: the ordinary-year average is built from 13 filings and the storm-inclusive average from 13 filings, out of 13 filings that published an outage figure at all. Those are the same utilities on both sides. A utility that filed without publishing a metric, or whose two major-event variants contradicted each other, is absent from that metric rather than counted as zero.

Reported interruption metrics for 2024, largest utility first.
Utility	Customers	Ordinary year	With major events	Interruptions
Northern States Power Co - Minnesota	104,471	64 min	100 min	0.7×
Black Hills Power, Inc.	73,846	57 min	57 min	0.9×
NorthWestern Energy - (SD)	64,209	66 min	76 min	0.6×
Sioux Valley SW Elec Coop	24,475	71 min	71 min	1.0×
West River Electric Assn Inc	21,594	44 min	44 min	0.5×
Watertown Municipal Utilities	14,404	3 min	3 min	0.1×
City of Brookings - (SD)	12,252	11 min	11 min	0.1×
Otter Tail Power Co	11,930	71 min	2.2 hr	1.0×
Black Hills Electric Coop, Inc	11,305	102 min	3.8 hr	0.8×
Montana-Dakota Utilities Co	9,258	2.5 hr	2.6 hr	1.4×
Northern Electric Coop, Inc	6,888	50 min	50 min	0.7×
Rosebud Electric Coop Inc	5,621	95 min	112 min	0.8×
MidAmerican Energy Co	5,299	42 min	7.1 hr	0.6×

What this page is not

It is a state average of utility filings, not a measurement at any address. Each filing is itself an average over a whole service territory, so a rural feeder and a downtown network arrive here as one number, and nothing in this dataset says how far an individual address sits from it. Nothing here predicts a future year either, and a single severe storm can move a utility’s figure by an order of magnitude.

The methodology page states the sources, the definitions, and the limits. Back to the Grid Reliability Index

Source: U.S. Energy Information Administration, Form EIA-861 reliability file, data year 2024, covering 2024-01-01 through 2024-12-31. The snapshot covers no later period.