County annual report · FIPS 30039
2021 Granite County, MT Power Outage Report
In 2021, customers in Granite County, MT went without power for an average of 9.7 hours, a total of 22K customer-hours (Montana average 5.0 hours). That ranks 13th worst of 51 Montana counties and 799th 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 Granite 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 | August 18, 2021 13:45 | August 18, 2021 21:45 | 8h | 910 | 2,335 |
| 2 | May 26, 2021 23:15 | May 27, 2021 02:30 | 3h 15m | 895 | 2,722 |
| 3 | July 20, 2021 05:00 | July 20, 2021 08:15 | 3h 15m | 895 | 2,347 |
| 4 | August 28, 2021 04:30 | August 28, 2021 07:15 | 2h 45m | 895 | 230 |
| 5 | January 13, 2021 18:00 | January 18, 2021 23:15 | 5d 5h | 450 | 5,043 |
| 6 | August 26, 2021 15:00 | August 26, 2021 18:45 | 3h 45m | 390 | 1,167 |
| 7 | December 27, 2021 20:00 | December 28, 2021 00:30 | 4h 30m | 210 | 945 |
| 8 | September 7, 2021 19:00 | September 7, 2021 23:45 | 4h 45m | 154 | 693 |
| 9 | June 27, 2021 19:00 | June 27, 2021 23:45 | 4h 45m | 149 | 434 |
| 10 | July 20, 2021 21:15 | July 21, 2021 02:30 | 5h 15m | 147 | 601 |
Outage episodes by size in 2021: 14 reached 100+ customers, 0 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 Granite 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 |
| Missoula Electric Coop, Inc | 2021 | 12.7 hrs | 3.21 | 6.5 hrs | 2.76 |
| Bonneville Power Administration | - | - | - | - | - |
| NorthWestern Energy | - | - | - | - | - |
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 ÷ 2,293 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. Granite County has data for 2019–2025.
Cite this report
MassOutage (massoutage.com), Granite 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/granite-county