THREE MILE ISLAND
OperatingNuclear power plant
- Capacity
- 976 MW
- Primary fuel
- Nuclear
- County
- Dauphin County
- Operator
- EXELON NUCLEAR
- Status
- Operating
- Commissioned
- 1974
- EIA plant ID
- 8011
- Coordinates
- 40.1545, -76.7249
THREE MILE ISLAND, a 976 MW Nuclear power plant in Dauphin County, Pennsylvania. Operated by EXELON NUCLEAR, commissioned 1974.
Weather peril exposure
THREE MILE ISLAND is a 976 MW nuclear power plant in Dauphin County, PA, operated by EXELON NUCLEAR, commissioned in 1974. Dauphin County carries low modeled catastrophe exposure in the FEMA National Risk Index, scoring 1.3 of 5 at the 9th national percentile. Hurricane is the leading peril, rated Relatively Moderate by FEMA at the 77th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a nuclear plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Dauphin County hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Hurricane | Relatively Moderate | 77th | 4.1 of 5 | 0.07 |
| Riverine flooding | Relatively High | 70th | 3.8 of 5 | 2.0 |
| Earthquake | Relatively Low | 58th | 3.3 of 5 | <0.01 |
| Winter weather | Very High | 50th | 3.0 of 5 | 12.3 |
| Tornado | Relatively Moderate | 29th | 2.1 of 5 | 0.28 |
| Strong wind | Relatively High | 16th | 1.6 of 5 | 4.7 |
| Wildfire | Very Low | 12th | 1.5 of 5 | <0.01 |
| Hail | Very Low | 11th | 1.4 of 5 | 2.2 |
| Lightning | Relatively High | 10th | 1.4 of 5 | 35.2 |
| Ice storm | Relatively Low | 9th | 1.3 of 5 | 0.58 |
| Heat wave | Relatively Moderate | 7th | 1.3 of 5 | 5.1 |
Perils not assessed in Dauphin County
These perils carry no usable National Risk Index figure for this county, so they are excluded from the scoring rather than scored zero. A zero would claim the peril was assessed and found benign.
| Peril | Why it is not scored |
|---|---|
| Coastal flooding | FEMA rating is "Not Applicable" for this county |
Model hail, wind and flood exposure for Dauphin County in the weather risk calculator
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.