County annual report · FIPS 30043
2021 Jefferson County, MT Power Outage Report
In 2021, customers in Jefferson County, MT went without power for an average of 4.8 hours, a total of 26K customer-hours (Montana average 5.0 hours). That ranks 27th worst of 51 Montana counties and 1363rd of 2,974 nationally.
Compared with MT, the US and 2020
Coverage line is EAGLE-I's share of Montana customers tracked each year.
Biggest outages in Jefferson County, 2021
The 10 outage episodes with the most customers out at once. Times are UTC.
| # | Started (UTC) | Ended (UTC) | Duration | Peak out | Customer-hours |
|---|---|---|---|---|---|
| 1 | March 9, 2021 18:15 | March 9, 2021 19:30 | 1h 15m | 1,694 | 1,758 |
| 2 | October 25, 2021 16:45 | October 25, 2021 21:15 | 4h 30m | 566 | 1,118 |
| 3 | October 7, 2021 17:45 | October 7, 2021 22:30 | 4h 45m | 565 | 1,839 |
| 4 | March 12, 2021 06:15 | March 12, 2021 09:30 | 3h 15m | 485 | 1,576 |
| 5 | July 21, 2021 22:00 | July 22, 2021 02:15 | 4h 15m | 473 | 659 |
| 6 | July 16, 2021 00:30 | July 16, 2021 07:00 | 6h 30m | 361 | 724 |
| 7 | January 13, 2021 19:45 | January 15, 2021 15:45 | 1d 20h | 233 | 4,240 |
| 8 | January 9, 2021 18:30 | January 9, 2021 19:30 | 1h | 211 | 211 |
| 9 | June 18, 2021 14:15 | June 18, 2021 21:00 | 6h 45m | 199 | 1,343 |
| 10 | April 8, 2021 03:00 | April 8, 2021 05:00 | 2h | 192 | 321 |
Outage episodes by size in 2021: 16 reached 100+ customers, 1 reached 1,000+ customers, 0 reached 10,000+ customers.
Utility reliability filed with the EIA
SAIDI (average outage time per customer) and SAIFI (average interruptions per customer) that utilities serving Jefferson County reported on EIA Form 861 for 2021, or their most recent earlier filing. Utility-wide figures, not county-specific.
| Utility | EIA year | SAIDI | SAIFI | SAIDI excl. major events | SAIFI excl. major events |
|---|---|---|---|---|---|
| NorthWestern Energy LLC - (MT) | 2021 | 2.5 hrs | 1.37 | 2.1 hrs | 1.18 |
| Bonneville Power Administration | - | - | - | - | - |
| NorthWestern Energy | - | - | - | - | - |
| Vigilante Electric Coop, Inc | - | - | - | - | - |
About this data
- Outage figures come from DOE/ORNL EAGLE-I, which records customers out by county every 15 minutes. EAGLE-I tracked about 76% of Montana's customers in 2021; utilities it does not see are not counted.
- Hours per customer = outage customer-minutes ÷ 5,322 customers (ORNL modeled county customer count), including major storm days. It is comparable across counties but is not the SAIDI a utility files.
- An outage event is a continuous stretch with customers out; counts at 100, 1,000 and 10,000+ use its peak.
- Years loaded: 2015–2025. Jefferson County has data for 2019–2025.
Cite this report
MassOutage (massoutage.com), Jefferson County, MT annual power outage report, 2021, data as of Oct 3, 2026 02:41 UTC, sources: DOE EAGLE-I (https://eagle-i.doe.gov/); EAGLE-I modeled customer counts (MCC) (https://figshare.com/); EIA Form 861 (utility reliability) (https://www.eia.gov/electricity/data/eia861/). https://massoutage.com/reports/2021/montana/jefferson-county