Gas and Nuclear: A Comparison of Two Local Plants

By Meredith Angwin

Many recent speeches (and blog posts) have compared nuclear and gas as sources of electricity generation for our future.  In this post, I will bring the comparisons closer to home, describing some of the similarities and differences between the Vermont Yankee nuclear power plant in Vernon, Vt., and the Granite Ridge Combined Cycle power plant near Manchester, N.H. Which technology is the future: gas or nuclear? Or are they both the future?

Overview of the plants

Vermont Yankee is a 620-MW boiling water reactor nuclear power plant, owned by Entergy Corporation. It was commissioned in 1972. Entergy owns more than 40 power plants in the United States (natural gas, nuclear, coal, and oil), as well as an extensive distribution system.

Granite Ridge is a modern combined cycle gas turbine plant (CCGT) whose maximum output varies between 660 MW and 790 MW, depending on the season. It went online in 2003. The plant was built by AES, a multi-national company that owns 34 power plants and an extensive distribution system in the U.S., and further holdings in 27 countries.

The ILEAD Energy Safari course visited Granite Ridge on November 8.  Bob Hargraves wrote an excellent blog post about that visit, including many pictures.

The public face of the two plants

Everyone in New England knows that Vermont Yankee exists:  It is always in the news. The plant also operates several websites, including:

In contrast, few people know that the Granite Ridge plant exists.  It is seldom in the news, and does not have its own website.

Vermont Yankee nuclear power plant


Vermont Yankee is located on the Connecticut River near Vernon Dam. It gets its cooling water from Vernon Pond (the lake behind the dam).



Granite Ridge gas power plant

Granite Ridge is tucked away in an industrial park. It gets its cooling water from the Manchester sewage treatment plant. The round object near the forefront of the Granite Ridge picture is a tank of yogurt from the StonyField Farms yogurt factory next door.

In the picture, you can also see that Granite Ridge has relatively low stacks. The plant does an excellent job of cleaning NOx, so the stacks emit only carbon dioxide and water. They do not need to be very high. Also, the plant is located in an industrial park on the flight path to the Manchester airport, which necessitates building height restrictions at the site.

Plant economics

Vermont Yankee is a major employer in its region, employing 650 people.

In contrast, a shift of four people can operate Granite Ridge. My guess is that Granite Ridge employs less than 100 people.

Working principle of a combined cycle power plant (Legend: 1-Electric generators, 2-Steam turbine, 3-Condenser, 4-Pump, 5-Boiler/heat exchanger, 6-Gas turbine)

Granite Ridge has 50-percent thermal efficiency, higher than any coal or nuclear plant. Though the plant is efficient and the price of natural gas is at historic lows, natural gas remains a high-end fuel. This means that natural gas plants are dropped from the mix when the grid doesn’t need much power. Power prices on the grid are frequently below Granite Ridge’s break-even point. The Energy Safari group was told that the plant does not operate as steadily as it would like to operate.

Granite Ridge is not a “peaker” plant, but it can easily move output up or down 5 MW a minute. It is frequently instructed to “load-follow” by the grid operator. Vermont Yankee is a “base load” plant, and thus usually runs at 100 percent. Both are very reliable plants.

Vermont Yankee is running steadily after 40 years, operating under a power purchase agreement put in place in 2002. This agreement gives Vermont Yankee about 4.5 cents per kWh. Granite Ridge is trying to be profitable and keep running while having the advantage of historically low gas prices. I believe that Granite Ridge sells at the market price, which goes above and below 4.5 cents quite regularly. For example, at late afternoon Friday, November 18, the local grid day-ahead market was 3.7 cents per kWh, while the real-time market was 5.1 cents per kWh.

Which is the future?

In my opinion, the future balance between gas and nuclear will basically be determined by whether or not Americans consider carbon dioxide to be important. Americans are quite willing to do small personal things to lower emissions (e.g., replacing light bulbs). We do not, however, tend to take carbon dioxide seriously when it comes to choices about power plants.

Granite Ridge is an impressive plant, with excellent control of NOx, and high thermal efficiency. It can load-follow, and it is using sewage treatment effluent as cooling water. Plants like this will be part of the future.

But the whole future? First, all fossil fuels carry carbon dioxide and climate change concerns. Second, grid operators do not like to see the grid overly dependent on a single fuel source, especially one like natural gas with major price volatility. The grid needs a mix of plants. Nuclear and natural gas must both be part of that mix.



Meredith Angwin is the founder of Carnot Communications, which helps firms to communicate technical matters. She specialized in mineral chemistry as a graduate student at the University of Chicago. Later, she became a project manager in the geothermal group at the Electric Power Research Institute (EPRI). Then she moved to nuclear energy, becoming a project manager in the EPRI nuclear division. She is an inventor on several patents.

Angwin serves as a commissioner in the Hartford Energy Commission, Hartford, Vt.  Angwin is a long-time member of the American Nuclear Society and coordinator of the Energy Education Project. She is a frequent contributor to the ANS Nuclear Cafe.

9 thoughts on “Gas and Nuclear: A Comparison of Two Local Plants

  1. bill eaton

    Thanks for the well stated article. In comparing nuclear and natural gas, the issue is not a competitive technology comparison for the reasons stated below as much as it is a statement of how complimentary nuclear and natural gas generation are today in support of a transistion away from higher emitting technologies (coal and oil).
    The utilities that will decide on nuclear versus natural gas versus coal will always look at the long term outlook for fuel and other variable costs and will decide on those with less volatility as a means of justifying/supporting their business case. Price volatility has a greater negative impact on base load generation than it does on load following or peaking generation for obvious market price reasons. And, in the case of nuclear, with the economics of the new and available designs, you will buy a 1300-1500 MW base load plant in any case. In the case of natural gas, the flexibility of using the generation in load following along with lower initial capital investment will follow historical patterns until more burdensome variable costs of emissions controls are placed upon coal.With that said, the prognosis for natural gas versus nuclear will still be weighted heavily on the experience base and the infrastrucutre of the parent utility. In other words, those that have nuclear will be the ones that build the new ones. In my region of the country (mid-south) the aversion to coal is not yet risen to the political leverage point and new coal is under construction. I agree that natural gas and nuclear will not only remain complimentary, but may in fact evolve differently in the next ten years as utilities not in a position to build nuclaer baseload may be stimulated to build natural gas base load as an alternative to coal. In any case, the wider understanding of the economics of natural gas and the market pressures that will come with more gas generation will likely make nuclear even more attractive to the investor. That could mean a return to the investment in nuclear facilites owned by multiple utilities and operated by one larger one. Thanks again for the article and its insights.

  2. Meredith Angwin

    Thank you for the comment. I read the book, and I think Robert Byrce may be right. However, I would like to see nuclear expand while we are using gas, rather then later, after the gas runs out.

  3. Robert Hargraves

    Robert Bryce, “Power Hungry”, believes in “N2N” — that is natural gas to nuclear. The US will burn more and more natural gas, eventually turning to nuclear.

  4. Rod Adams

    Meredith – I have visited fossil fuel burning power plants for my entire life. I have nearly always found that they are operated by the same kind of dedicated, safety conscious “salt of the earth” types that I loved to work with in the sea-going Navy.

    I have also had the privilege of working at somewhat “higher” corporate and organizational levels. Though most of the people who inhabit office suites and board rooms are individually pretty decent people, my overall impression is that they are far more motivated by numbers and dollars than by care for their fellow human beings or pride in doing important work well.

    The good people who work at the Granite Ridge plant are probably not activists who fight useful industrial infrastructure assets like the Vermont Yankee power station. Most of them would be offended by the waste and the loss of a good employer. On the other hand, the people at the CLF are all about winning and capturing more resources for their clients even if that hurts people who are not their clients.

  5. Meredith Angwin

    Marcel. I also think methanol is part of the future. However, right now, natural gas is inexpensive and methanol simply can’t compete.

    Rod, you are correct. Conservation Law Foundation’s profit-making arm, CLF Ventures, helped arrange the siting permits for Granite Ridge, and are quite proud of it.

    Though, as you can see by following the links in the post above, and reading the comments, CLF Ventures isn’t actually for-profit. Supposedly. Very confusing.

    When I saw the article you linked, from the free library, I was puzzled. 1200 acres of conservation land will adjoin the Granite Ridge plant? Huh? The plant is located in a small industrial park. Maybe Granite Ridge made some cash grant to the town for conservation, but the story sounds as if the plant is surrounded by forests, not by yogurt factories and sewage treatment plants. Again, very confusing.

    Of course knocking out Vermont Yankee will raise the average price on the grid and cause this plant to be more profitable! CLF is definitely looking after the interests of its fave technology by attacking Vermont Yankee.

    It turns out that a CLF Board of Directors member took the Energy Safari class, and he and I “had words” in front of the whole class, right before the Granite Ridge visit! He didn’t like me saying that the CLF support of this plant and attack on Vermont Yankee were probably related! Oh dear. Vermont is a small town! However, this person also said he personally doesn’t think CLF should do things like help site Granite Ridge, because it does leave them open to criticism. So we agree, at that level. He is a good, sincere man, and I like him. I hope he likes me!

    Also, Granite Ridge was a very gracious host. The people working at the plant were highly professional and very safety-oriented. We are truly grateful for the opportunity to visit the plant. In my blog post, I didn’t want to include the issues of who advocated for the plant, back in the early 2000s. Still, the advocacy story is part of the mix of what happens with energy, and I am glad you included a reference to it.

  6. Rod Adams


    The break even point for the gas plant may be proprietary information, but it is not difficult to compute the fuel cost relationship given the data that you provided.

    A natural gas plant that achieves a thermal efficiency of 50% requires 7500 BTUs of heat input for every kilowatt-hour of electricity it produces. That means that any time the market price for electricity is less than 0.0075 times the delivered cost of a million BTUs of natural gas at the power plant, the operators of the plant are paying more just to purchase fuel than they are receiving for selling electricity.

    If natural gas costs $5 per million BTU to deliver, the barest minimum price that Granite Ridge needs to charge for power – without paying employees or paying back any of the capital costs – is 3.75 cents per kilowatt hour. If the delivered price of gas goes up to $10, a situation that is not uncommon in New England during periods of high gas demand, the minimum price for electricity from Granite Ridge would be 7.5 cents per kilowatt hour.

    I guess that means that I disagree with one of your statements – the future balance between natural gas and nuclear may well be determined by the market demand driven price behavior of natural gas, even if we do not put a price on CO2 dumping into the atmosphere.

    My bet is that the average market price of natural gas during the course of each year will be considerably higher in New England if the forces arrayed against Vermont Yankee succeed in forcing its production out of the market.

    If the price of gas goes up and if ENVY is not available to supply low priced power, Granite Ridge may spend more time “in the money” and operating to supply higher priced electricity, thus paying off its capital cost with a higher annual rate due to cost saving effect of higher capacity factors.

    Didn’t I read somewhere that the Conservation Law Foundation (CLF), a stout Vermont Yankee opponent, has a profit-making arm called CLF Ventures that was heavily involved in the effort to construct the Granite Ridge combined cycle plant.…-a091037951

  7. Marcel F. Williams

    The nuclear industry’s biggest mistake, IMO, is their failure to at least build demonstration projects for the production of hydrogen for synthetic hydrocarbon fuel production. Because of the need for peak load electricity production, nuclear power plants will never completely replace natural gas power plants unless nuclear power plants are also utilized to produce peak load synthetic fuels like methanol.

    The nuclear production of methanol from hydrogen and CO2 (from biowaste or extracted from the atmosphere) could allow nuclear power plants to fuel methanol electric power plants for peak load electricity production. Methanol can also be converted into gasoline, diesel fuel, and jet fuel for transportation.

  8. Meredith Angwin

    Thank you for your comments, John!

    The gas plant did not tell us the number of employees, just that it only took a minimum of four per shift to run the plant. I figured that was a minimum of 28 employees for all the shifts, but clearly they have more employees. So I used 100 as my number.

    We were not trying to find out proprietary information. “How many employees” might be something they don’t want to share. “Just what IS your set-point for selling power?” is not a question plants want to answer. See our Safari blog posts for wind, biomass, etc. They didn’t answer that question. Still, most articles comparing types of plants don’t actually visit the the plants. So I felt this comparison was worth making, even if it is not complete.

    I think we need both types of plants.

  9. John Grosso

    1. I didn’t notice the comparison of capital costs of the 2 plants equated to a similar point in historical construction of the plants.
    2. Also, the gas plant suffers price penalties for being more flexible and being able to start up and shut down. The nuclear plant lacks this flexability.
    3.It was a surprise to see the difference in labor costs of 100 employees vs 650 employees between the 2 plants.
    4. Also, the differences in insurance costs for liability coverage should be included.
    Obviously we need both types of plants.

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