solar vs nuclear

Solar vs. nuclear: battle for the best carbon-free power

Over the last few years, solar capacity in the United States has truly taken off. Over 58 gigawatts (or million kilowatts) of solar capacity are currently installed across nearly 2 million projects, and at least 3.7 gigawatts more are in the pipeline as of late 2018. At the same time, the fate of nuclear power in the country is at a crossroads. Only one single nuclear unit has been completed in the U.S. since the 1990s, and the two most recent projects are experiencing delays, cost overruns, and ultimately cancellations.

With both nuclear and solar energy making headlines recently, it’s worth a deeper dive into how each power source stacks up against the other. While both are carbon-free sources of electricity, the big similarities end there. This article compares how much each power source costs, how much energy they produce, how long they last, and importantly, how long each resource takes to build.

Cost and time to build solar vs. nuclear power

The biggest differences between solar and nuclear power are the cost and time it takes to build each type of generating facility. Nuclear power is much more expensive and takes much longer to bring online.

The recent history of nuclear power construction in the U.S. provides a useful point of comparison. Only a single nuclear power plant has been completed in the U.S. in the last 30 years: the two-unit Watts Bar Nuclear Plant in Tennessee, which required 23 years for one reactor to be operational and 33 years for the other. What’s more, the two most recent nuclear projects under construction — the Vogtle Electric Generating Plant and the V.C. Summer Nuclear Station — received approval in 2012 from the Nuclear Regulatory Committee (NRC), and are both over budget and far from completing construction. For instance, a revised cost forecast for the Vogtle plant projects a total project cost of $25 billion, which is a 75 percent increase over its original $14.3 billion estimate.

In the six years since the approval of the Vogtle plant and V.C. Summer station, the Solar Energy Industries Association lists 57 utility-scale solar projects of at least 100 megawatts (MW) that have come online, with 14 additional 100-plus MW projects currently under construction. One such project currently under construction, the 250 MW Phoebe Solar Project in Texas, is scheduled to cost $397 million and take less than one year to bring online.

These stark differences are echoed in the most recent Levelized Cost of Energy Analysis by Lazard, a leading financial advisory and asset management firm. Their findings suggest that the cost per kilowatt (KW) for utility-scale solar is less than $1,000, while the comparable cost per KW for nuclear power is between $6,500 and $12,250. At present estimates, the Vogtle nuclear plant will cost about $10,300 per KW, near the top of Lazard’s range. This means nuclear power is nearly 10 times more expensive to build than utility-scale solar on a cost per KW basis.

Interestingly, Lazard also forecasts the construction time required to build the different facilities and finds that utility-scale solar takes nine months to complete, while nuclear may take 69 months to build. Given the recent experience of building nuclear power in the U.S., 69 months (or slightly less than six years) might be optimistic. In fact, the revised estimated operational dates for the two units of the Vogtle plant are now 2021 and 2022, a full decade after the plant received approval from the NRC.

Deciding to build solar vs. nuclear power

Consider a hypothetical scenario where an energy developer must decide to begin construction of a new nuclear power plant or to build utility-scale solar farms. The developer can decide to build one single 2,430 MW nuclear unit in 10 years or to build as many 250 MW solar farms as possible within that same 10-year time period. If the goal is to add as much carbon-free electricity to the grid as possible, which option should they choose?

The clear choice is utility-scale solar. Because one new 250 MW solar farm can be built every nine months, a total of 14 utility-scale solar farms could be built sequentially and back-to-back within the same decade it takes to build one nuclear power plant. The result of these 14 solar projects would be 3,500 MW of utility-scale solar, which equals 46 percent more carbon-free generating capacity per decade of construction. What’s more, whereas the nuclear power plant comes online all at once, building utility-scale solar generates nine additional years of solar electricity while waiting for the one nuclear facility to finish construction (see graph).

solar vs nuclear capacity over time

Importantly, this hypothetical scenario assumes that only one utility-scale solar facility is built at a time, as opposed to the nearly sixty 100-plus MW solar farms that have been completed since the Vogtle plant received its approval in 2012. From a cost perspective, the 3,500 MW of solar capacity will cost around $3.3 billion, which is less than one-seventh of the cost of the $25 billion dollar Vogtle nuclear plant.

Creating an apples-to-apples comparison

There’s more to the comparison of solar vs. nuclear power than costs, capacity, and construction timelines. One of the most important factors to consider is how much energy each produces per year.

Power sources have two key characteristics: capacity, which is a measure of the power that a source can output in megawatts, and generation, which is a summation of the amount of energy that a power source can supply to an electric grid in a given time period (measured in megawatt-hours, or MWh). For instance, an incandescent light bulb requires 60 watts of power, and keeping that light on for an hour requires 60 watt-hours of energy.

A measure of how much energy a certain power source puts onto the grid is its “capacity factor,” which calculates how close to the maximum amount of possible annual generation a source produces. For instance, a nuclear power plant will run at its max until it needs new fuel, which may be six or twelve months later. As such, nuclear has a capacity factor of close to 100 percent because it typically produces as much generation as possible during every hour of the year. Solar power, on the other hand, can only produce electricity when the sun is out. This means that over the course of the year, solar power plants will produce their maximum amount of generation in just 17 to 20 percent of total hours, on average.

In other words, the 2,430 MW Vogtle nuclear plant could be expected to generate 21 million MWh per year, enough to power about 1.75 million residential households. The 3,500 MW of hypothetical solar power from the example above would produce just under 6 million MWh of electricity per year, enough to power 500,000 homes.

For solar to produce as much electricity as is generated by the 2,430 MW Vogtle nuclear plant it would require about 13,000 MW of utility-scale solar capacity, nearly four times as much as built in the above example. However, the cost to build that capacity would be $12.4 billion, which is still just 50 percent of the cost of the $25 billion Vogtle nuclear plant.

Solar: more capacity in less time for less money

As this hypothetical scenario explains, solar projects can be built in substantially less time and at a much lower cost than a single nuclear project. Even when accounting for capacity built and energy produced from a nuclear facility, large-scale solar farms remain much less expensive and quicker to bring online than nuclear. As governments and utilities across the U.S. plan for the next century of power generation, utility-scale solar easily bests nuclear as the leading source of carbon-free power.

This post originally appeared on Earth 911.

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About Spencer Fields

Spencer is the Manager of Market Strategy & Intelligence at EnergySage, where he's able to showcase his expertise around all things energy. Prior to joining EnergySage, he spent five years at Synapse Energy Economics, providing environmental, economic and policy analysis for public interest groups. Spencer has degrees in Environmental Studies and Hispanic Studies from Brown University, meaning when he's not in the office you can find him outside or traveling somewhere to work on his Spanish.

7 thoughts on “Solar vs. nuclear: battle for the best carbon-free power

  1. vince

    California right now uses lots of wind and solar, Denmark is similar. Yet it has very high electricity prices. But OK lets ignore that

    When it is a non windy night, the only reason why california and Denmark do not have blackouts is because it can import power from other neighboring states. Similar things happen for Denmark. The only reason these neighbors have spare electricity is because they have fossil fuel, fission and hydro. What happens when all your neighbors get rid of all their fossil fuel and fission and also rely on wind and solar and the entire area is non windy and it is night time?
    Sure you can rely on storage in theory but there is a reason why California uses imports mostly and only has tiny amounts of storage. Same thing for Denmark and Denmark also uses large amounts of wood instead of storage. Wood that is imported long distances and which displaces carbon stored in old growth forests with much lesser carbon stored in tree plantations with young trees.

  2. vince

    Lazard’s LCOE may be wrong. To put it briefly, if you look at older versions of Lazard’s report, in the graph there are end notes that say that they only took the value from an AP100 reactor. The newer reports omit this end note but the value is not that different, slightly higher.

    You use only one gen 3+ reactor design from a country that is known to have the highest nuclear construction costs. I don’t think you can generalize that to other countries and other reactor designs.

  3. Ben Bethel

    Another thing to consider… 1) the cost to decommission a nuclear power plant… Arizona’s Palo Verde Nuclear Generating Station will cost $130 *billion* to decommission… And 2) it uses enough water each year to cover Phoenix (over 500 square miles) in 26.4 inches of water each year… Not wise for a hot desert city that is in a horrible drought, and the cost of the water will increase. This water could feed the needs of the 5th largest city in the united states.

  4. Kees

    Besides the above arguments, one must also not forget that the life span of a modern nuclear plant is around 75 years while solar panels are around 25 years. Also, in the 25 year life span, the solar panels gradually lose efficiency. Thus making solar in the example above much more expensive than nuclear. (3 x 12.4 billion vs 25 billion)

  5. Stanley Tolle

    Not a good comparison. Nuclear produces 24 hour power while solar produces power only when the sun shines. Solar also produces it’s power for the most part when demand and prices paid for generated power are low. So maybe something like the value of power produced should be considered vs the cost of that power. Done this way nuclear comes out much better particularly when longer time frames are used. This is, however, if one assumes the same type of nuclear plants that were built in the past, strict baseload plants. Like a high tempature molten salt plant can be built with high tempature salt energy storage that can make it a plant that produces power for times of high power demand and high prices for generated power. When this possiblity is considered the economics of nuclear starts to look allot better.

  6. Chris

    Thank you for this comparison. A few points.
    Using the Watts Bar reactors to talk about build time is misleading at best. Most of that time no construction was taking place.
    Pricing solar generation without including the price of the backup generation or storage is also not a valid comparison. That backup generation and storage has its own global warming and material footprint.

  7. Scott

    Great report except you left out one of the biggest detractors for solar in comparison to nuclear.
    How much land for 2500MW for both nuclear and solar?
    Solar takes at least NINE TIMES the amount of space that nuclear does.


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