The energy transition is one of the most pressing challenges of our time, and the comparison between nuclear energy and renewable sources such as solar, wind, and hydropower has become a hot topic. When analyzing the latest data and the arguments that dominate public and scientific debate, it is essential to understand how each energy source ranks in terms of cost, efficiency, environmental impact, and future potential.
This article compiles and expands on information from the best studies, reports, and specialized portals, focusing on the Spanish context but with global data. This article offers a clear and up-to-date overview of the advantages and disadvantages of nuclear energy versus renewables, while also integrating technical and socioeconomic nuances that often go unnoticed in many analyses.
Current overview of electricity generation in Spain and around the world
Renewable sources have substantially increased their weight in the energy mix, both nationally and internationally. According to the latest data from Red Eléctrica de España (REE), renewables accounted for 2024% of the electricity generated in the country in January 52,1, equivalent to more than 12.200 GWh. Wind energy leads the way with 24,6%., followed by hydropower (17,4%) and solar, which, although its percentage is not specified, has experienced meteoric growth in recent years. Nuclear power, meanwhile, accounted for 22% of the supply, lagging behind the main renewables combined.
This change of leadership in the energy landscape This is no coincidence. Technological advancement, cost competitiveness, and regulatory incentives have boosted solar and wind energy in particular, making them more affordable and accessible for both investors and consumers.
What do we mean by renewable energies and how are they classified?
Renewable energies are those obtained from inexhaustible natural sources. or with the capacity to regenerate in the short term. The main ones include wind, solar (photovoltaic and thermal), and hydropower. Biomass and geothermal energy complete the group, although their specific weight is lower in the Spanish and European context.
- Clean: They generate very little waste and do not emit greenhouse gases in their operations.
- Inexhaustible: They come from sources such as the sun, wind or water, whose natural flow is not depleted by human consumption.
- Native: They allow us to take advantage of the resources available in each territory, reducing dependence on foreign countries.
- No hazardous waste: Unlike nuclear power, they do not leave behind long-lasting toxic or radioactive materials.
In contrast, conventional sources (among which nuclear has mixed characteristics) have historically been:
- Contaminants: Especially fossil fuels, although nuclear power emits very little CO2 during operation.
- Limited: By depending on finite raw materials (uranium, gas, coal, oil).
- Dependents from abroad: Especially in the case of Spain, which imports almost all of its uranium for nuclear power.
- Producers of hazardous waste: In the nuclear case, radioactive waste that requires management for thousands of years.
What makes nuclear energy different?
Nuclear energy is generated from the fission (and in the future, fusion) of atomic nuclei of elements such as uranium and plutonium. Its main advantage is the ability to produce large amounts of electricity continuously., without depending on weather conditions and without emitting CO2 during its generation cycle.
Nuclear power plants present a high energy density. This means that with a relatively small amount of fuel, they can generate huge amounts of electricity. In addition, its operation is constant (except for technical shutdowns), which provides stability to the electrical system.
However, nuclear It faces considerable challenges such as radioactive waste management, high construction and decommissioning costs, and the potential risk of major accidents. (Historical cases such as Chernobyl and Fukushima remain present in the collective memory and in international regulations). For more information on these aspects, you can consult the environmental impact of nuclear energy.
Cost comparison: Who is more competitive today?
One of the most relevant aspects for investors, governments and citizens is the levelized cost of energy (LCOE). This indicator measures the total cost of building and operating a plant divided by all the electricity it will generate over its useful life. It allows different technologies to be compared on equal terms.
According to data from the World Nuclear Industry Status Report (WNISR) and the World Nuclear Association (WNA), Levelized costs of solar energy have fallen by 90% in the last decade, and those of wind energy by 72%.Nuclear energy, for its part, has reduced its cost by only 36% since 2009, and in some cases, it has increased due to high safety requirements and project complexity. For a more in-depth analysis, you can visit benefits and risks of nuclear energy.
- Solar energy: $36 per megawatt hour (MWh).
- Wind power: $38 per MWh.
- Nuclear energy: $67 per MWh (almost double that of major renewables).
Renewables have a clear advantage, as their costs continue to fall steadily., while nuclear power requires high initial investments and long construction times (on average, 7 to 9 years).
Construction time and return on investment
Renewable energy facilities can be built in much shorter timeframes. than a nuclear power plant. For example, a wind or solar farm can be operational in a matter of months or a couple of years, while a nuclear plant requires 7 to 9 years of construction (in some cases, longer). To better understand how these facilities work, we recommend How a nuclear power plant works.
During this period, the invested capital remains "idle," which represents a significant opportunity cost. Furthermore, Regulatory and technological uncertainty could make the start-up of new nuclear plants even more expensive., while renewables often benefit from regulations that incentivize their deployment.
Generation capacity, availability and efficiency
One of the most used arguments in favor of nuclear power is its constant supply capacity, which allows for continuous electricity supply, regardless of the weather or time of dayRenewable energy, on the other hand, depends on wind power, solar radiation, or river flow, which makes their production more variable. To learn more about how a nuclear power plant works, you can visit .
However, recent data show that Installed capacity and annual production of renewables already exceed nuclear energy in many countries.For example, solar power has a global capacity of between 848 and 942 GW, while wind power is around 823,5 GW (2021 data). Based on annual production, wind power generates 1850 TWh and solar power 1032 TWh each year, making wind power the world leader in renewable electricity production.
In Spain, the trend is even more marked., with the sum of wind and hydropower almost doubling the contribution of nuclear power in some months, according to data from 2024.
Investment Analysis: How Much Do the Same Euros Invested Yield?
Comparative studies, such as that conducted by the Department of Electrical Engineering at the Polytechnic University of Valencia, offer a revealing perspective. For every €4.000 billion invested, a 1 GW nuclear power plant can generate approximately 7.423 GWh annually. The same amount invested in wind energy (where the cost per GW installed is €600 million) allows for the installation of 6,666 GW, which, even operating 2.000 hours per year, produce 13.333 GWh annually (179% more energy). To better understand the investment potential in renewables, see .
In the case of solar photovoltaic energy, which currently costs around €1.200 billion per GW installed, the same €4.000 billion would allow for the construction of a 3,333 GW plant, capable of generating around 5.333 GWh annually in an average location like Alicante. In regions with higher radiation, this figure increases significantly. The maintenance and fuel costs of solar plants are also almost zero compared to nuclear plants..
This analysis shows that Investment in wind and solar power is significantly more efficient from an economic and energy perspective., without taking into account the problems of waste management and the risks associated with nuclear energy.
Advantages and disadvantages of nuclear energy compared to renewable energy
Main advantages of nuclear energy
- High energy density: It can generate huge amounts of electricity in a small physical space, ideal for countries with territorial limitations.
- Constant electricity: Its production is independent of weather conditions, ensuring a stable and predictable supply.
- Low GHG emissions: Virtually zero during operation, key in decarbonization scenarios.
- Conversion efficiency: High efficiency in the transformation of fuel into electricity.
Key disadvantages of nuclear power
- Radioactive waste management: It generates hazardous waste that must be stored safely for thousands of years, with technological and social uncertainty. For more details, see Nuclear radiation.
- High initial and maintenance costs: Construction, operation, and decommissioning involve high outlays and long payback periods.
- Risk of serious accidents: Although the probability of accidents is low, they have disastrous consequences, as demonstrated by the historical cases of Chernobyl and Fukushima.
- Dependence on imported materials: Spain, for example, imports most of the uranium needed for its power plants.
- Proliferation problems: Nuclear technology and materials can be diverted for military purposes, adding to the geopolitical concern.
Advantages of renewables over nuclear energy
- Decreasing cost and greater competitiveness: Solar and wind power have massively reduced their costs and are now more profitable than nuclear power for new plants.
- Lower environmental and social impact: They do not generate hazardous waste or risk of major accidents.
- Ease and speed of deployment: They allow for increasing installed capacity in short periods of time.
- Autonomy and less external dependence: Spain, for example, can exploit its natural resources (sun and wind) without depending on imports.
The role of hydraulics and the integration of renewables
Hydropower, although its growth is limited by the availability of water resources, remains fundamental to the Spanish electricity system, allowing large amounts of energy to be stored and regulating the grid. In particularly rainy months, its contribution can exceed 17% of total production, as was the case in January 2024..
Renewable energy as a whole, thanks to the complementarity of different technologies and advances in storage solutions (batteries, pumped hydro), are increasingly capable of guaranteeing stable and sustainable coverage for electricity demand.
Critical points and future challenges
Despite the strength of renewables, there are still challenges: variability of solar and wind power It requires advanced backup, interconnection, and storage systems. The upgrade of the electrical grid and regulatory reforms accompany the process.
For its part, nuclear energy faces pressure from public opinion, rising costs and the climate urgency This requires rapid and scalable solutions to decarbonize the economy. Although some experts defend its usefulness as part of the transition mix, the global trend points toward an accelerated expansion of renewables, particularly due to their lower cost and their ability to reduce dependence on imported and polluting sources. For more information on nuclear energy, see .
Technological advances, falling costs, and the increased integration of renewable energy mean that, in practical terms, the future of the global electricity system clearly points toward more sustainable, efficient, and indigenous solutions, leaving behind the dependence on technologies with higher risks and costs.
