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America’s top electricity-producing power plants

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Kent Knutson's picture
Energy Market Specialist Hitachi Energy USA Inc.

Kent Knutson is a market specialist focusing on energy industry intelligence for Hitachi Energy.  He has more than 30 years of experience designing and developing intelligence products for some...

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The key to a reliable power grid is the diversity of energy supply.  The combination of all types including fossil, nuclear, hydro, wind, solar, and other renewable resources like geothermal and biofuels all help to balance the grid and keep overall costs lower for customers.  Today’s electricity industry is experiencing rapid change as the industry transitions to a lower-carbon future.  Through the transition, it is important to recognize the energy contribution all resources in the fuel mix are making. 

The most prolific power plants in the U.S. have a few things in common including high energy output, relatively high capacity factors, and, if the plants burn fossil fuel, low overall heat rates.  Along with big contributing fossil and nuclear power plants, there are some outstanding performances by wind and solar farms in the mix. 

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These rankings are the result of research by Hitachi Energy’s Velocity Suite team.  The analysis compares power plants by type and by fuel.  Type refers to the prime mover technology like combined-cycle, steam, gas turbines, nuclear reactors, hydro turbines, wind turbines, and solar photovoltaic systems.  Natural gas combined-cycle units are the most efficient at converting fuel into electricity.  The most heavily run are nuclear reactors that commonly record higher than 90% capacity factors with several units approaching 100% over an entire year. 

The indicators

The capacity factor is the measure of how often a power plant runs for a specific period. It’s expressed as a percentage and calculated by dividing the actual unit electricity output by the maximum possible output. This ratio is important because it indicates how fully a unit’s capacity is generating electricity.  For the purposes of this analysis, the capacity factor is determined using the ‘seasonal’ capacity in the denominator which can vary substantially between winter and summer months for individual generators. 

Heat rate is the amount of energy used by an electrical generator/power plant to generate one kilowatt-hour (kWh) of electricity.  Heat rates are commonly expressed in British thermal units (Btu) per net kWh generated.  The lower the heat rate value the more efficient the generator is at converting fuels into electricity.   Combined Cycle natural gas units record the lowest average heat rates among fossil fuel systems generally running about one-third less than similar-sized steam units running on coal and natural gas.

U.S. natural gas and coal generation (MWh) and heat rate (Btu/kWh) by prime mover 

In the United States, over the past decade, the average annual capacity factor of natural gas combined-cycle units has increased from around 50% to about 60% today.  During the same period, steam coal units have declined from around 60% on average to around 40%.  Nuclear reactors continue to run above 90% while wind and solar farms have improved to the mid-40% and mid-30% respectively.

U.S. electricity capacity factor by fuel source, %

Driven by coal plant closures and the availability of competitively priced natural gas, electricity producers in the U.S. have dramatically increased natural gas in the fuel mix.  In 2020, natural gas accounted for an annual record of 40.5% of the generation mix.  Despite the high growth in wind and solar electricity production, the recent increase in gas prices, combined with supply shortages, is expected to push coal back into the mix in 2021.  Historically when gas prices have increased coal has filled the gap and 2021 is not an exception.  Through August 2021, coal was up 26.7% (135.0 million MWh) from the same period in 2020.  Wind and solar are up as well 13% (37.0), while natural gas has declined 5% (-55.8). 

U.S. electricity production by fuel source, TWh

So how do the various types of power plants perform and how do they compare? 

The top U.S. generating power plants by fuel and prime mover

Natural gas combined cycle

Most of the large generating natural gas combined cycle (NGCC) power plants reside in the southeastern U.S.  Of the top-10 power plants, four are in Florida, one in Georgia, and one in Alabama.  There are two large facilities in Virginia and one in Arizona also making the list.  All top-10 NGCC plants recorded average annual heat rates between 6,600 and 7,400 Btu/kWh – extremely efficient.  The top generating natural gas plant in the nation is NextEra Energy’s mammoth West County Energy Center located on a 220-acre site in western Palm Beach County, Florida.  The three-unit facility totaling about 3,700 MW generated 19.7 million MWh in 2020.  Southern Company’s Jack McDonough (18.7) and Franklin (12.6) represented the second and third highest power producers in 2020.  The two plants are in Georgia and Alabama respectively.  Two Duke Energy-owned power plants in Florida fill out the top five spots.  They are Crystal River (11.7) in Citrus County and the Hines Energy Complex (11.6) in Polk County.

Top 10 U.S. electricity-producing natural gas combined cycle (CC) plants, annual performance in 2020

Coal steam

Topping the list of Top-10 largest producing steam coal power plants is Ameren Corp’s Labadie Station in Missouri.  In 2020, the power plant generated 16.5 million MWh running at an average annual seasonal capacity factor of 77.4% with an average heat rate of 10,602 Btu/kWh.  Close behind Labadie Station is Southern Companies James H Miller Jr plant (16.4) located on 800 acres in West Jefferson, Alabama.  The next three largest electricity-producing steam coal plants are DTE Energy’s Monroe (13.2) MI, Vistra Energy’s Oak Grove Steam Electric Station (13.1) TX, and ArcLight Capital Partner’s Gavin (13.1) OH.

Top 10 U.S. electricity-producing coal steam (ST) plants, annual performance in 2020  

Gas turbines

Six of the Top-10 largest gas turbine (GT) power producers are in Texas with ExxonMobil Corporation’s Beaumont Refinery leading the way.  In 2020, the Beaumont facility generated about 3.3 million MWh.  The next four facilities in the Top-10 ranking of GT producers include Phillips 66’s Sweeny Cogeneration Facility (3.1) TX, ExxonMobil’s Baytown Turbine Generator Project (2.8) TX, Consolidated Edison’s East River (2.5) NY, and Air Liquide Group’s Bayou Cogeneration Plant (2.3) TX. 

Top 10 U.S. electricity producing natural gas turbine (GT) plants, annual performance in 2020  

Nuclear

During 2020, the Top-10 nuclear-producing power plants generated an astounding 225 million MWh.  For perspective, consider that the total power production from all hydroelectric resources in 2020 totaled 291 million MWh – this coming from over 2,000 operating hydropower plants compared to only 10 nuclear facilities.  Topping the list was Arizona’s behemoth Palo Verde Nuclear Generating Station at 31.6 million MWh, Alabama’s Browns Ferry (28.8), Texas’s South Texas (22.0), Pennsylvania’s Peach Bottom (21.8), and South Carolina’s Oconee power plant (21.5).  

Top 10 U.S. electricity-producing nuclear plants, annual performance in 2020  

Conventional Hydro

Topping the list of the Top-10 largest hydro power-producing plants in America is the US Bureau of Reclamation’s Grand Coulee in eastern Washington state.  In 2020, the 80-year-old hydro facility generated 20.3 million MWh – about one-fifth of all power generated in the state of Washington which is home to five of the Top-10 largest generating hydropower plants in the country.  New York is residence to two of the Top-10 including the second-ranked New York Power Authority (NYPA) Robert Moses Niagara hydro project (17.5) and the sixth-ranked, NYPA’s R.H. Saunders (Moses) Power Project (7.8).  Two projects in the northwest, both operated by the U.S. Corp. of Engineers, are in positions 3 and 4.  They are Chief Joseph (11.9) in Douglas County, Washington, and John Day (8.5) in Sherman County, Oregon.

Top 10 U.S. electricity-producing conventional hydropower plants, annual performance in 2020  

Wind turbines

The largest generating wind farm in the U.S. is the Alta Wind Energy Center spanning 3,200 acres in Kern County, California.  The project is owned by Terra-Gen Power, an affiliate of Arclight Capital Partners and Global Infrastructure.  In 2020, Alta Wind, also known as the Mojave Wind Farm, produced about 3 million MWh.  NextEra Energy owns the next three largest producing wind farms including Horse Hollow (2.5) TX, Capricorn Ridge Wind Farm (2.3) TX, and the Limon Wind Energy Center (2.1) CO.  Rounding out the top five projects is Axium Infrastructure Inc.’s Meadow Lake Wind Farm (2.1) spread over Benton and White Counties, Indiana.  The most efficient, in terms of an average annual capacity factor in 2020, was Xcel Energy’s Hale County Wind Project (49.6%) located near Plainview, TX. 

Top 10 U.S. electricity-producing wind farms, annual performance in 2020  

Solar photo-voltaic

The largest power-producing solar PV facility in the U.S. is Consolidated Edison’s Copper Mountain Solar plant in Boulder City, Nevada.  In 2020, the facility produced roughly 1.4 million MWh.  Following in positions 2 through 5 was Berkshire Hathaway’s Topaz Solar Farm (1.3) CA, NextEra Energy’s Desert Sunlight Solar (1.3) CA, Consolidated Edison’s Mesquite Solar (1.1) AZ, and 8 Minute Solar’s Springbok Solar Farm (0.95) CA. The most efficient in terms of the annual average capacity factor was the Desert Sunlight Solar project (32.7%) in the Mojave Desert near the town of Desert Center in Riverside County, California.

Top 10 U.S. electricity-producing solar farms, annual performance in 2020  

What will the 2021 Top U.S. plants list look like? 

We will know in a matter of months.  The recent expansion of wind and solar capacity across the country is sure to result in some shuffling among the largest wind and solar farms. In 2020, and through October 2021, there have been 1,097 solar (85.5%) and wind (14.5%) projects that have been brought online, according to research by the Hitachi Energy Velocity Suite research team.  Topping the list of newly operating wind farms are CMW Energy’s Aviator Wind (525 MW) in Texas, Enel Green Power North America’s Cheyenne Ridge Wind Farm (500 MW) in Colorado, and Invenergy’s Sagamore Wind Project (527 MW) in Texas. Topping the list of large solar farms to start operations since 2020, are Orsted’s Eunice Solar and Storage Project (427 MW), Longwood Energy Holding’s Prospero I and II (379 MW), and Copenhagen Infrastructure Partner’s Greasewood Solar Project (255 MW) – all located in Texas. 

America’s top generating electric power plants are diverse and important contributors to keeping the grid energized and balanced.  We’ll be keeping an eye on how they continue to perform.

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Matt Chester's picture
Matt Chester on Nov 11, 2021

When going through this data, did you get a sense for how the production and capacity factor related to year of install? That is, are plants built more recently successfully moving up the list of the most productive plants thanks to new tech and strategies? 

Bob Meinetz's picture
Bob Meinetz on Nov 11, 2021

Kent, though Exxon-Mobil's Beaumont Refinery may have generated 3.2 TWh of electricity at an extraordinary 80% capacity factor, comparing it to plants that generated electricity for public consumption is apples/oranges.

Presumably the vast majority of that energy (if not all) was consumed by the refinery itself. With few transmission losses and without any need to meet independent demand, of course it will have outstanding "performance" - at helping to make the fuels causing climate change. And hopefully both the refinery and the plant generating its electricity will be completely unnecessary, sooner than later.

Roger Arnold's picture
Roger Arnold on Nov 12, 2021

I doubt very much that the greater part of the Beaumont power plant was consumed by the refinery itself. Refineries don't consume all that much electrical energy. Thermal energy, I believe, is what they consume most heavily. They get that by burning natural gas and off-gas from the refinery process itself. You're probably right, however, that little of Beaumont's electrical power would have been sold for distribution to public consumers. Baseload power, in general is more often sold on long term contract to industrial users. Or to energy traders betting that they can wheel it to the wholesale market at a profit.

 

I don't see that any of that really matters much. Capacity factor for dispatchable assets is more a function of market demand than technology. The marginal cost of generation for wind and solar assets is zero -- or negative, due to PTCs and RECs. Those resources bid into the wholesale market at their marginal cost of generation, and then receive the clearing price for the auction. If there will be sufficient wind and solar capacity to meet demand for the period covered by the auction, then the clearing price will be zero or negative. All resources with above-zero marginal generation costs will be shut out. That includes any baseload generation that has not been pre-sold on long term contract. 

 

CCGTs have the highest efficiency and lowest carbon footprint of any generation from fossil fuels. They are 50% more efficient than simple combustion turbines. But they have twice the capital cost. As grid penetration of variable renewables rises, it's increasingly difficult for these expensive, high-efficiency assets to sell their output. They have to shut down, even thought there's still a need for the capacity that they represent. The low CF available for high-efficiency assets playing backup to variable renewables drives a trend toward reliance on lower efficiency but cheaper simple combustion turbines. It's hard to quantify, but declining efficiency of the backup fleet constitutes a hidden carbon footprint for variable renewables.

Bob Meinetz's picture
Bob Meinetz on Nov 12, 2021

3.3 TWh/yr works out to an average of 375 MW. Although Exxon claims Beaumont can generate up to 500MW, they're probably running the plant steadily at 375 GW to maximize efficiency and selling what they don't need to the grid as a "price taker" (bidding $0/MWh, and taking what they can get).

 

Jim Stack's picture
Jim Stack on Nov 12, 2021

Kent, Great data but I think you are looking at the wrong items. It's not the capacity factor it is the over system from fuel supply to pollution and matching of the consumer need to production.  An example is a coal power plant. It can't be ramped down and then back up to meet the high peak demand to the low off peak demand. The same for Nuclear.   Compare that to how a Solar power plant makes the most when you need the most power and then shuts down at night when your use is at it's lowest. Pair that with Hydro that produced the same power day and night and you have the perfect renewable synergy.

Solar and Wind also don't use any water. And water is becoming more a key item every day. 

Bob Meinetz's picture
Bob Meinetz on Nov 13, 2021

"Compare that to how a Solar power plant makes the most when you need the most power and then shuts down at night when your use is at it's lowest."

Peak electricity consumption in the U.S. is ~ 8PM in the winter and ~6:30 PM in the summer, when solar is consistently generating no electricity at all (at least at night it's consistent),

"Solar and Wind also don't use any water." 

Modern nuclear plants don't consume any water either, Jim. Diablo Canyon is a closed-loop system that returns every drop of the 2 billion gallons of salt water is uses for cooling every day to the Pacific Ocean - from whence it came.

Kent Knutson's picture
Kent Knutson on Nov 16, 2021

Thanks for all the comments.  The story is not meant to compare all categories of generation resources (apples to oranges) -- it's meant to highlight the top electricity producers in each category by prime mover and fuel (apples to apples).  The capacity factor and heat rate are meaningful within the prime mover fuel category only.  I found it interesting that the Top-10 nuclear power plants generate more than one-quarter of all nuclear power in the country . . . now that is impressive.  Thx again for your comments.    

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