States › South Dakota › NorthWestern Energy
investor-owned utility · EIA utility 13809
NorthWestern Energy
Average price is revenue divided by sales for the sector and year; it is not a tariff rate. Reliability figures are as reported by utilities to EIA on Form 861 and may use different calculation methods. Annual figures: Form EIA-861 for 2024, final release. Monthly state figures run to July 2026.
NorthWestern Energy serves 51,467 residential customers in South Dakota as an investor-owned utility, according to its 2024 Form EIA-861 filing, with a service territory that touches 27 counties.
Its average residential price that year was 12.56¢ per kilowatthour, about the same as the South Dakota average of 12.86¢ and 24% below the US average of 16.48¢. The figure is residential revenue divided by residential sales, so it folds in fixed charges, riders and every rate schedule the utility bills under.
That works out to an average residential bill of $113.36 a month on average use of 903 kWh a month. Across South Dakota the average bill was $127.81 on 994 kWh, so a bill gap reflects how much power households use as well as what each kilowatthour costs.
For reliability it reported a SAIDI of 76.0 minutes per customer with major event days included and 66.5 minutes with them excluded, calculated under IEEE 1366 standard. The median among South Dakota utilities reporting was 73.7 minutes with major event days; this utility's figure is 3.1% above that median.
The average price is up 18.4% on 2019, against up 11.3% for South Dakota as a whole, and up 11.5% on 2023. EIA's early release for 2025, which has not been fully edited, shows 13.35¢.
Compared with South Dakota, the US and other investor-owned utilities
| Measure, 2024 | This utility | Investor-owned utilities, US median | South Dakota | United States |
|---|---|---|---|---|
| Average residential price per kWh | 12.56¢ | 16.17¢ | 12.86¢ | 16.48¢ |
| Average monthly residential bill | $113.36 | $131.47 | $127.81 | $142.26 |
| Average monthly use, kWh | 903 | 787 | 994 | 863 |
| Residential price change, 1 year | +11.5% | — | +4.4% | +3.0% |
| Residential price change, 5 years | +18.4% | — | +11.3% | +26.7% |
| SAIDI, all events (minutes) | 76.0 | 278.7 | 73.7 median | 184.5 median |
| SAIDI, without major event days | 66.5 | 106.5 | 65.1 median | 99.8 median |
State and US prices, bills and use are EIA's own averages over every customer. The ownership column and the reliability columns are medians across utilities with at least 1,000 residential customers, computed on this site from the final 2024 file. Among the 6 filings by investor-owned utilities in South Dakota, the median price was 13.22¢. In South Dakota this utility's price ranks 10 of 20, counting from the highest.
Average price by year
NorthWestern EnergySouth Dakota averageUS average
Year by year
| Year | ¢ per kWh | South Dakota ¢ | Monthly bill | kWh a month | Residential customers | All sales |
|---|---|---|---|---|---|---|
| 2025 early release | 13.35¢ | 13.38¢ | $125.34 | 939 | 51,787 | 1.7 TWh |
| 2024 | 12.56¢ | 12.86¢ | $113.36 | 903 | 51,467 | 1.7 TWh |
| 2023 | 11.26¢ | 12.32¢ | $110.36 | 980 | 51,261 | 1.7 TWh |
| 2022 | 11.71¢ | 12.09¢ | $113.91 | 973 | 51,069 | 1.7 TWh |
| 2021 | 11.45¢ | 12.22¢ | $107.32 | 937 | 50,805 | 1.7 TWh |
| 2020 | 11.40¢ | 11.75¢ | $109.43 | 960 | 50,646 | 1.7 TWh |
| 2019 | 10.61¢ | 11.55¢ | $102.83 | 969 | 50,615 | 1.7 TWh |
| 2018 | 10.73¢ | 11.59¢ | $105.79 | 986 | 50,547 | 1.7 TWh |
| 2017 | 11.04¢ | 11.77¢ | $99.91 | 905 | 50,248 | 1.6 TWh |
| 2016 | 10.46¢ | 11.47¢ | $95.58 | 913 | 50,016 | 1.6 TWh |
| 2015 | 8.98¢ | 11.08¢ | $82.77 | 922 | 49,807 | 1.5 TWh |
| 2014 | 8.71¢ | 10.47¢ | $85.18 | 978 | 49,590 | 1.6 TWh |
| 2013 | 8.38¢ | 10.26¢ | $82.11 | 980 | 49,297 | 1.6 TWh |
Bundled residential service only in the price, bill and use columns. Bill = residential revenue ÷ customers ÷ 12; use = residential sales ÷ customers ÷ 12. EIA describes its early release as not fully edited; it is shown for this utility alone and enters no average, median or rank on this site.
Month by month
NorthWestern EnergySouth Dakota average
Sales by sector, 2024
| Sector | Customers | Sales | Share of sales | Revenue | ¢ per kWh, bundled |
|---|---|---|---|---|---|
| Residential | 51,467 | 557.5 GWh | 33% | $70,012,000 | 12.56¢ |
| Commercial | 13,444 | 668.8 GWh | 40% | $80,339,000 | 12.01¢ |
| Industrial | 60 | 438.7 GWh | 26% | $34,748,000 | 7.92¢ |
Customers, sales and revenue count every service type the utility reported (bundled, energy-only and delivery-only). The price column uses bundled service alone, because part-bill revenue would understate it. Sources of energy: 3.1 TWh in total, of which 35% was its own net generation and 2 TWh was bought wholesale; summer peak demand 326 MW.
Reliability
Minutes of sustained interruption per customer in 2024, as the utility reported them under IEEE 1366 standard. SAIFI: 0.70 interruptions per customer with major event days, 0.65 without; CAIDI 107.9 minutes per interruption. EIA's South Dakota total across all reporting utilities was 84.7 minutes with major event days and 62.1 without. Major event days are storms and similar events that a utility's chosen method sets apart; methods differ, so treat comparisons as approximate. What SAIDI and SAIFI mean.
| Year | SAIDI, all events | SAIDI, no major events | SAIFI, all events | SAIFI, no major events | Method |
|---|---|---|---|---|---|
| 2025 early release | 119.7 | 81.6 | 1.14 | 0.85 | IEEE 1366 |
| 2024 | 76.0 | 66.5 | 0.70 | 0.65 | IEEE 1366 |
| 2023 | 116.5 | 73.9 | 1.37 | 1.03 | IEEE 1366 |
| 2022 | 127.8 | 79.6 | 1.26 | 1.01 | IEEE 1366 |
| 2021 | 91.3 | 81.4 | 0.95 | 0.83 | IEEE 1366 |
| 2020 | 159.0 | 112.6 | 1.54 | 1.28 | IEEE 1366 |
| 2019 | 173.0 | 112.0 | 1.74 | 1.39 | IEEE 1366 |
| 2018 | 111.0 | 97.0 | 1.24 | 1.13 | IEEE 1366 |
| 2017 | 109.0 | 84.0 | 1.41 | 1.24 | IEEE 1366 |
| 2016 | 126.0 | 85.0 | 1.42 | 1.14 | IEEE 1366 |
| 2015 | 102.0 | 93.0 | 1.07 | 0.95 | IEEE 1366 |
| 2014 | 90.0 | 82.0 | 1.00 | 1.00 | IEEE 1366 |
| 2013 | 128.2 | 69.5 | 1.01 | 0.84 | IEEE 1366 |
Generation at plants it operates, 2025
- Wind 64.5% 282.3 GWh
- Natural gas 35.5% 155.2 GWh
Net generation of 437.5 GWh at power plants this utility operates, from Form EIA-923. It is not the mix delivered to customers: utilities also buy power wholesale (2 TWh in 2024), sell generation to others and may co-own plants that another company operates.
Counties in its service territory
- Aurora County
- Beadle County
- Bon Homme County
- Brown County
- Brule County
- Charles Mix County
- Clark County
- Codington County
- Davison County
- Day County
- Deuel County
- Douglas County
- Edmunds County
- Faulk County
- Hamlin County
- Hand County
- Hanson County
- Hughes County
- Hutchinson County
- Hyde County
- Jerauld County
- Kingsbury County
- Marshall County
- Sanborn County
- Spink County
- Turner County
- Yankton County
Counties the utility listed on Form EIA-861 for 2024. Listing a county does not mean the utility serves all of it.
Other utilities in South Dakota
| Utility | Ownership | Residential customers | ¢ per kWh | Monthly bill | SAIDI, all events | SAIDI, no major events |
|---|---|---|---|---|---|---|
| Black Hills Power, Inc. | Investor-owned | 62,981 | 14.33¢ | $110.12 | 55.5 | 55.5 |
| Sioux Valley SW Elec Coop | Cooperative | 25,583 | 12.87¢ | $172.31 | 64.4 | 64.4 |
| Southeastern Electric Coop Inc | Cooperative | 20,160 | 12.41¢ | $139.98 | 71.3 | 71.3 |
| West River Electric Assn Inc | Cooperative | 18,423 | 14.25¢ | $127.85 | 43.5 | 43.5 |
| Watertown Municipal Utilities | Municipal | 11,633 | 9.30¢ | $79.62 | 3.3 | 3.3 |
| City of Brookings | Municipal | 10,544 | 11.12¢ | $89.79 | 10.6 | 10.6 |
| Black Hills Electric Coop, Inc | Cooperative | 9,227 | 14.76¢ | $163.70 | 228.7 | 102.0 |
| Central Electric Coop, Inc | Cooperative | 6,483 | 13.64¢ | $201.08 | — | — |
All South Dakota utilities · Investor-owned utilities nationwide
Questions and answers
How much does electricity cost from NorthWestern Energy?
Residential customers paid an average of 12.56¢ per kilowatthour in 2024. EIA derives this by dividing residential revenue by residential sales; it is an average across all rate schedules and charges, not a tariff rate.
How does that compare with South Dakota?
The South Dakota average residential price in 2024 was 12.86¢ and the US average 16.48¢; NorthWestern Energy was about the same as the state figure. Among 20 utility filings with a bundled residential price in South Dakota, it had the 10th highest.
What is the average NorthWestern Energy bill?
$113.36 a month in 2024, on average residential use of 903 kWh a month (annual revenue and sales divided by customers and by twelve). The South Dakota average was $127.81 on 994 kWh.
How reliable is NorthWestern Energy service?
It reported 76.0 minutes of interruption per customer (SAIDI) including major event days and 66.5 minutes excluding them, with 0.70 interruptions per customer (SAIFI) in 2024. Utilities calculate these under differing methods, so comparisons are approximate.
Is the NorthWestern Energy price rising?
The average residential price was up 11.5% in 2024 compared with 2023 and up 18.4% compared with 2019. EIA's early, not fully edited release for 2025 shows 13.35¢.
Which counties does NorthWestern Energy serve?
Its Form EIA-861 service territory lists 27 counties, including Aurora County, SD, Beadle County, SD, Bon Homme County, SD, Brown County, SD, Brule County, SD and Charles Mix County, SD. A county can appear in several utilities' territories.
Provenance
Source: U.S. Energy Information Administration. Annual figures are from Form EIA-861 (sales to ultimate customers, reliability, operational data and service territory files), final release for 2024, respondent "NorthWestern Energy - (SD)", utility number 13809; the 2025 row is from EIA's early release. Monthly utility figures are from the Form EIA-861M sample. State and US averages are from the Form EIA-861M sales and revenue workbook, published through July 2026. Generation by fuel is from Form EIA-923, 2025 final. All are US government works in the public domain. Page built 30 Sep 2026. Errors in processing are corrected at the next build; see corrections. For tariffs and rate schedules, consult the utility or the state utility commission.