Nameplate and summer capacity explained
Nameplate capacity is the rating stamped on a generator by its manufacturer; net summer capacity is what the operator says the unit can actually deliver to the grid during summer peak, after its own plant use. Across all US generators in the 2025 EIA-860 data, summer capacity comes to 93% of nameplate. The gap is small for solar, wind and hydro and large for gas turbines and geothermal.
Every plant page on this site leads with nameplate capacity and shows summer capacity next to it. Rankings always use nameplate, so that a plant is never compared on two different measures.
The ratio by technology
| Technology | Units | Nameplate | Net summer | Summer as share |
|---|---|---|---|---|
| Gas combined cycle | 1,857 | 313.4 GW | 282.3 GW | 90% |
| Coal steam | 445 | 182.2 GW | 168.0 GW | 92% |
| Gas combustion turbine | 2,237 | 160.2 GW | 135.5 GW | 85% |
| Onshore wind | 1,565 | 159.5 GW | 158.8 GW | 100% |
| Solar photovoltaic | 7,968 | 152.9 GW | 151.9 GW | 99% |
| Nuclear | 96 | 103.7 GW | 98.4 GW | 95% |
| Gas steam turbine | 549 | 83.1 GW | 76.4 GW | 92% |
| Hydro | 3,951 | 80.0 GW | 79.9 GW | 100% |
| Battery | 1,003 | 43.6 GW | 43.3 GW | 99% |
| Oil-fired | 3,801 | 30.5 GW | 26.3 GW | 86% |
| Pumped-storage hydro | 150 | 22.2 GW | 23.0 GW | 104% |
| Wood and wood waste | 271 | 8,011 MW | 7,104 MW | 89% |
| Gas engine | 1,849 | 7,299 MW | 7,027 MW | 96% |
| Geothermal | 163 | 4,049 MW | 2,684 MW | 66% |
| Municipal solid waste | 73 | 2,265 MW | 1,891 MW | 84% |
| Other gases | 67 | 1,947 MW | 1,773 MW | 91% |
| Other | 83 | 1,655 MW | 1,474 MW | 89% |
| Landfill gas | 1,210 | 1,587 MW | 1,493 MW | 94% |
| Other waste biomass | 199 | 659 MW | 577 MW | 88% |
| Other natural gas | 177 | 344 MW | 337 MW | 98% |
Why gas turbines lose the most
A combustion turbine breathes air, and hot air is thin. On a summer afternoon the same machine moves less mass through its compressor and produces less power, which is why gas combustion turbines report summer capacity at 85% of nameplate. Combined-cycle plants recover part of that loss in their steam section and sit at 90%. Coal steam units (92%) and nuclear units (95%) lose less, mostly to their own pumps, fans and cooling systems, which run on the plant’s output.
Geothermal has the lowest ratio in the table, 66%: taken together, geothermal units report only about two thirds of their rated output as available in summer. EIA-860 records the two numbers but not the reason for the gap.
Why solar, wind and hydro look identical
For solar photovoltaic, wind and most hydro units, summer capacity is reported at or very near nameplate. For solar, the nameplate in EIA-860 is the inverter (AC) rating, which is also the most the plant can push to the grid. That does not mean these plants deliver their full rating on a summer day; how much the sun, wind or river supplies is a separate question that EIA-860 does not answer.
When summer is higher than nameplate
Some units report summer capacity above nameplate. Of the units of 50 MW or more with both figures, 465 do. The survey records both numbers as the operator reports them and does not ask why one exceeds the other. During cleaning, this site set aside 40 summer values that were negative or above 1.6 times nameplate; nameplate was kept for those units.
Which number to use
Use nameplate to compare the size of equipment and to match other EIA-860 statistics. Use summer capacity when the question is how much a plant can deliver at summer peak demand. For the full definitions see how to read the data; for plant sizes in nameplate terms see how big is a US power plant.
How big the gap is overall
Added up across the country, nameplate exceeds net summer capacity by 91.0 GW. Natural gas units account for 69% of that difference, more than any other fuel. By state, the ratio is lowest in Kentucky, where summer capacity is 86% of nameplate, and highest in Washington at 98%. The difference follows each state’s mix: fleets with a large gas share sit low, fleets of hydro, wind and solar sit near 100%.
Large plants with the widest gap
Among plants of 500 MW or more that report summer capacity for every unit, these have the lowest summer share. Their plant pages show both figures for each unit, so the units that pull the ratio down are easy to spot.
| Plant | State | Main fuel | Nameplate | Net summer | Summer share |
|---|---|---|---|---|---|
| Geysers Unit 5-20 | California | Geothermal | 1,236 MW | 644 MW | 52% |
| Goose Creek Energy Center | Illinois | Natural gas | 684 MW | 432 MW | 63% |
| Gleason Generating Facility | Tennessee | Natural gas | 568 MW | 360 MW | 63% |
| Montana Power Station | Texas | Natural gas | 527 MW | 352 MW | 67% |
| Kingston | Tennessee | Coal | 1,700 MW | 1,147 MW | 67% |
| Lincoln Combustion | North Carolina | Natural gas | 2,156 MW | 1,485 MW | 69% |
| Sonoran Solar Energy | Arizona | Solar | 750 MW | 520 MW | 69% |
| White Bluff | Arkansas | Coal | 1,800 MW | 1,253 MW | 70% |
Storage and missing values
Storage plants follow the same rule as generators: the summer figure is what they can discharge to the grid. Pumped-storage hydro units report 104% of nameplate in summer taken together, and battery units 99%. Neither number says how long the plant can keep discharging; EIA-860 records that separately for batteries, and this site does not use it.
Not every unit reports a summer figure. Of the 27,866 operable units in the data, 112 have no usable summer value, either because none was reported or because it failed the cleaning rule above. When any unit of a plant lacks the figure, the plant page shows nameplate only and leaves the summer total out instead of adding up an incomplete number. The notes on the data list every cleaning rule with the number of records it touched.
Source: U.S. Energy Information Administration, Form EIA-860 (Annual Electric Generator Report), 2025 final data (Sep 2026). Downloaded 2026-10-28. Figures are computed by GridPlants from the plant, generator and ownership files; see how to read the data.