Three Mile IslandOut of service
Dauphin County, Pennsylvania · EIA plant ID 8011 · Operator: Exelon Nuclear
Nameplate981MWSummer 803 MW
Generators1in service
Net generation—GWh12 mo
Capacity factor—no 923 generation in the last 12 months
Heat rate—thermal plants only
First online1974
Monthly net generation
EIA-923, all units at the plant. Net of station use; storage can go negative.
FinalPreliminary
Capacity factor by year
Net MWh ÷ (summer MW × hours), primary-fuel units. Each year uses that year's EIA-860 ratings; the hollow dot is the latest 12 months.
Heat rate by year
Electric fuel MMBtu × 1000 ÷ net MWh (Btu/kWh, HHV), fossil units only; CT + CA counted as one combined-cycle block.
Heat rate applies to fuel-burning (thermal) units only.
Annual data table
| Year | Net GWh | Capacity factor | Heat rate (Btu/kWh) |
|---|---|---|---|
| 2001 | 5,416.8 | 75.8% | — |
| 2002 | 7,313.5 | 102.3% | — |
| 2003 | 6,197 | 90.0% | — |
| 2004 | 7,273.2 | 102.2% | — |
| 2005 | 6,755.5 | 98.1% | — |
| 2006 | 7,227 | 105.0% | — |
| 2007 | 6,645.3 | 96.5% | — |
| 2008 | 7,365.1 | 106.7% | — |
| 2009 | 5,888.9 | 83.5% | — |
| 2010 | 6,633.8 | 94.1% | — |
| 2011 | 6,518.8 | 92.4% | — |
| 2012 | 7,038.3 | 99.5% | — |
| 2013 | 6,659.1 | 94.4% | — |
| 2014 | 7,327.6 | 104.2% | — |
| 2015 | 6,598 | 93.8% | — |
| 2016 | 7,082.7 | 100.4% | — |
| 2017 | 6,860.3 | 97.5% | — |
| 2018 | 7,335.8 | 104.3% | — |
| 2019 | 5,214.2 | 111.4% | — |
Generators
EIA-860 (annual) with EIA-860M updates through Sep 2026. EIA-923 reports generation by plant, prime mover and fuel, not by unit, so unit-level output isn't shown.
| Gen ID | Technology | Prime mover | Nameplate MW | Summer MW | Online | Status | Planned retirement | OEM / model |
|---|---|---|---|---|---|---|---|---|
| 1 | Nuclear | ST | 980.8 | 802.8 | Aug 1974 | Operating (Out of service) | — | coming soon |
Owner / operator
Operator: Exelon Nuclear. Ownership shares by in-service nameplate MW (EIA-860 Schedule 4; units not listed there are wholly owned by the operator).
| Exelon Nuclear | 100.0% | 981 MW |
Nearby plants
Within 80 km.
| York Haven | 20 MW | 4.3 km |
| Brunner Island | 1,616 MW | 6.6 km |
| Strinestown Solar | — | 7 km |
| Phoenix Contact - CCHP Plant | 1 MW | 9 km |
| Lancaster County Resource Recovery | 36 MW | 11.2 km |
| GSK York RDC Solar Facility | 3 MW | 12 km |