Nuclear and Renewables: Allies, not Enemies, for a Stable Grid
When looking at low-carbon energy options, there are four main contenders. Hydroelectric power is the most widely used carbon-free source, accounting for approximately 15% of global electricity generation, followed by nuclear energy at 9%, wind energy at 8%, and solar energy at 6%. While each energy source plays a role in reducing carbon emissions, nuclear energy is the most vital of the four. Nuclear energy’s ability to provide reliable baseload power sets it apart from its clean energy counterparts. Though valuable as flexible energy contributors, renewable energy sources cannot be relied upon to meet continuous energy demands.
The capacity factor is a measure of how efficiently an energy source, like a power plant, produces electricity compared to its maximum potential output. It is expressed as a percentage and represents the ratio of actual energy generated over a given period of time—typically a year—to the energy that would have been produced if the system operated at full capacity the entire time. Having a high-capacity factor is important because it directly relates to the reliability and efficiency of an energy source. In other words, the higher the capacity factor, the more consistently an energy source produces electricity. A high capacity factor means that an energy source can consistently generate electricity to meet demand.
Nuclear energy has the highest capacity factor of any energy source—carbon-free or otherwise. Solar energy has the lowest capacity factor with 25%, and wind and hydroelectric aren’t much better with about 35% and 42% respectively. All sources, even carbon-emitting ones like coal and natural gas, are dominated by nuclear energy’s staggering 92.5% capacity factor.
So what makes the capacity factor for nuclear power so high? Nuclear power plants have a high capacity factor because they are designed to run for long periods of time, usually about 1.5 to 2 years, before needing refueling—minimizing downtime and maintenance interruptions. In contrast, natural gas and coal plants experience more frequent stops for routine maintenance and fuel replenishment, lowering their overall capacity factors.2 Renewable energy sources such as wind and solar are limited by natural fluctuations in their fuel availability. In other words, it isn’t always windy or sunny enough. Hydroelectric power has a relatively low-capacity factor because its electricity generation depends on the availability of water, which can fluctuate seasonally.
Nuclear energy's high-capacity factor makes it an ideal baseload energy source. Baseload energy refers to the consistent, reliable electricity needed to meet the continuous demand of the power grid. This reliability ensures that, even when the energy demand grows or shrinks, nuclear can maintain a stable supply—supporting the grid's foundational energy needs. This energy goes toward acts like heating or cooling our homes and powering our hospitals, so it is crucial that we have a stable source.
Our other three carbon-free energy options don’t have high enough capacity factors to make them reliable options for baseload energy, but that doesn’t mean they’re bad. Solar, wind, and hydroelectric energy sources offer flexibility and can supplement the energy supply during peak demand. Their ability to generate power when conditions are favorable helps diversify the energy grid, reducing reliance on any single source.3 This diversification is important because it allows for a more stable grid, minimizing the risks associated with outages and unexpected disruptions. Renewables play a part in a clean energy future, but nuclear energy is vital because of its high capacity factor and ability to provide consistent, carbon-free power.
References
Low Carbon Power. (n.d.). Low carbon power. Retrieved from https://lowcarbonpower.org/
U.S. Department of Energy. (2022). Nuclear power: The most reliable energy source, and it's not even close. Retrieved from https://www.energy.gov/ne/articles/nuclear-power-most-reliable-energy-source-and-its-not-even-close
U.S. Department of Energy. (n.d.). Energy reliability. Retrieved from https://www.energy.gov/eere/energy-reliability
U.S. Energy Information Administration. (n.d.). Glossary. Retrieved from https://www.eia.gov/tools/glossary/?id=B
Visualizing Energy. (n.d.). What are capacity factors and why are they important? Retrieved from https://visualizingenergy.org/what-are-capacity-factors-and-why-are-they-important/
