IEA Scenarios and the Outlook for Nuclear Power
The energy projections produced by the International Energy Agency (IEA) are frequently consulted by policymakers, the media, and analysts. This information page discusses the nuclear power sector projections of the main IEA scenarios alongside those produced by other organizations.
Several scenarios are produced and regularly updated by the IEA to explore different versions of the future and the circumstances that could lead to them. Two main approaches are used to develop these scenarios:
- Exploratory – this method applies the effects of certain policies and actions being carried out to build up possible versions of the future.
- Normative – derives potential pathways needed to achieve a particular outcome by a given date.
The former approach (exploratory) provides a picture of what the future might look like if certain conditions are met. Usually a ‘business-as-usual’ scenario would be provided as a reference point to show what the outcome could be if current policies and plans were to continue their trend through the forecast period. The IEA’s Stated Policies Scenario (STEPS) – which is “designed to provide a sense of the prevailing direction of energy system progression, based on a detailed review of the current policy landscape” – is an example of this type of scenario.
World Energy Outlook scenarios
The IEA’s annual World Energy Outlook report relies on three main scenarios derived from its Global Energy and Climate (GEC) Model:
- The Stated Policies Scenario (STEPS) aims to describe the prevailing direction of the energy system, based on a sector-by-sector and country-by-country assessment of energy-related policies that are in place and under development.
- The Announced Pledges Scenario (APS) assumes that all climate commitments made by governments and industries around the world will be met in full and on time.
- The Net Zero Emissions by 2050 (NZE) Scenario provides a pathway for the energy sector that is consistent with the Paris Agreement target of limiting the increase in the global average temperature to 1.5 °C above pre-industrial levels.
The STEPS provides a more conservative benchmark than the APS as it assesses the likelihood of achieving the energy-related targets and aspirations that have been announced, whereas the APS takes for granted that these will be reached. The version of the APS that was updated in 2023 (that takes account of relevant policies and measures adopted by the end of August 2023) is associated with a temperature rise of 1.7 °C in 2100 (with a 50% probability), compared with 2.4 °C in the STEPS.
As exploratory scenarios, both the STEPS and APS are not designed to achieve a particular outcome. In contrast, the normative NZE Scenario provides a pathway to achieve a given target by a given date, i.e. net zero energy-related carbon dioxide emissions by the year 2050. By comparing the STEPS or APS with the NZE Scenario, it can be seen what additional measures and policies are needed to comply with the Paris Agreement.
In addition to government policy, the GEC Model takes into account many other influences on the energy sector such as technology costs, energy prices and affordability, as well as social, economic and demographic factors. The focus of this information page is on the comparison between the IEA’s nuclear capacity projections and those of the International Atomic Energy Agency (IAEA) and World Nuclear Association.
IAEA capacity projections
The 43rd edition of the IAEA’s annual Reference Data Series No. 1 report, titled Energy, Electricity and Nuclear Power Estimates for the Period up to 2050, contains estimates of energy, electricity and nuclear power trends up to the year 2050. The low case is essentially a ‘business-as-usual’ scenario where the current market, technology and resource trends continue. The high case assumptions are more ambitious, with policies on climate change also being taken into account.
The increased recognition of the nuclear sector’s contribution to mitigating climate change and strengthening energy security is reflected by the 14% increase in the low case and 2% in the high case compared with the 2022 edition of the report.
The IAEA quotes the 2022 nuclear capacity as 371 GWe from 411 operable reactors; a further 22.8 GWe from 24 units in Japan and four units in India are classed as ‘suspended operation’. This would increase to 458 GWe in the low case and 890 GWe in the high case by 2050.
Nuclear Fuel Report scenarios
The biennial Nuclear Fuel Report published by World Nuclear Association presents three exploratory scenarios for nuclear generating capacity, referred to as the Reference, Lower, and Upper Scenarios. The Reference Scenario is largely a reflection of current government policies and plans officially announced by utilities for nuclear over the next 10-15 years. The Upper Scenario is underpinned by more favourable conditions for nuclear development – including the acceptance that nuclear power will play an indispensable role in reaching net-zero carbon emissions by mid-century. The Lower Scenario, on the other hand, does not foresee a noticeable impact of climate change policy on nuclear power development and assumes that nuclear’s contribution to security of electricity supply and grid resilience (amongst other factors) is not sufficiently valued.
In the 2023 edition of The Nuclear Fuel Report, the projections for nuclear capacity in 2040 are 486 GWe (Lower), 686 GWe (Reference) and 981 GWe (Upper). The projections in all three scenarios were significantly higher than those in the 2021 edition of the report (449 GWe, 615 GWe and 839 GWe), reflecting the trend of improving prospects for nuclear power that began towards the end of the last decade.
The outlook period for these scenarios goes up to 2040. The projections for that year in the 2023 edition of the IAEA’s Reference Data Series No. 1 report are 434 GWe (low case) and 681 GWe (high case). Both the IAEA and World Nuclear Association projections follow very similar methodologies and assumptions, so a high level of consistency between these two organizations’ nuclear capacity projections should be expected. The assumptions used in the IAEA’s low case and high case broadly match those used in World Nuclear Association’s Nuclear Fuel Report for the Reference Scenario and Upper Scenario, respectively; however, the nuclear capacity projections for 2040 in the IAEA’s low case are 37% lower than those in The Nuclear Fuel Report’s Reference Scenario and the IAEA’s high case is 31% lower than The Nuclear Fuel Report’s Upper Scenario (see Figure 1).
Figure 1: IAEA and World Nuclear Association nuclear capacity projections
IEA nuclear capacity projections
The nuclear projections within the two main exploratory scenarios of the IEA – the Stated Policies Scenario (STEPS) and Announced Pledges Scenario (APS) – are based on broadly similar assumptions as those used in the IAEA’s and World Nuclear Association’s scenarios discussed above.
In the 2023 edition of the IEA’s World Energy Outlook (WEO 2023), nuclear capacity reaches 557 GWe in 2040 and 622 GWe in 2050 in the STEPS; and 677 GWe and 769 GWe in the APS (see Figure 1). Comparing the 2040 projected nuclear capacities in the STEPS and APS with the Reference and Upper Scenarios of The Nuclear Fuel Report, the IEA’s projections are 19% and 22% lower, respectively, than those of World Nuclear Association.
As an example of the IEA’s past performance, the 2000 edition of the World Energy Outlook presents one scenario, referred to as the Reference Scenario, which projects 2020 nuclear capacity to be 323 GWe. This figure is 14% below the actual figure of 375 GWe in 2020. As a comparison, the Reference Scenario in the 2000 update to The Global Nuclear Fuel Market (the former title of The Nuclear Fuel Report) was 5% higher (395 GWe) than the actual figure for 2020.
The differences in the projections between the two organizations demonstrate the degree of subjectivity involved in producing projections for future nuclear capacity.
NZE Scenario
There are many pathways that are consistent with the targets outlined in the agreement made at the 21st UN Climate Change Conference (COP21) in December 2015 (known as the Paris Agreement). One such pathway is the IEA’s Net Zero Emissions by 2050 (NZE) Scenario, introduced in the 2020 edition of the World Energy Outlook report and described in detail in Net Zero by 2050: a Roadmap for the Global Energy Sector, which was launched in May 2021.
By the time of the publication of the 2022 edition of the World Energy Outlook, the NZE Scenario had changed significantly. In the earlier report (i.e. the Roadmap), projected energy supply in 2050 (543 EJ) is 2% higher than in WEO 2022 (532 EJ); meanwhile projected total electricity generation (71,200 TWh) is 3% lower in the earlier report than in WEO 2022 (73,200 TWh). Projected nuclear capacity in 2050 is increased by 7% from 812 GWe in the 2021 report to 871 GWe in WEO 2022.
The Roadmap report was updated in September 2023 as Net Zero Roadmap: A Global Pathway to Keep the 1.5 °C Goal in Reach – 2023 Update. The NZE Scenario was again revised extensively. Projected energy supply in 2050 was slightly lowered to 541 EJ, while electricity generation increased by a further 5% to 76,800 TWh; and nuclear capacity was also up by 5%, to 916 GWe.
As the world proceeds on a path that will fall short of attaining net zero carbon emissions by 2050, normative scenarios with this target have to be frequently revised to account for the ongoing shortfall – resulting in increasingly more ambitious measures required to achieve that outcome.
Given the scale of the challenge, scenario modellers are faced with relying on early-stage technologies (e.g. nuclear fusion or hydrogen/ammonia fuel), or on increasing the deployment of existing technologies at highly ambitious rates. On the demand side, energy savings can be increased – though demand-side savings are likely to have already been assumed to an extent that compromises the scenario’s plausibility. The version of the NZE Scenario in the 2023 Roadmap (which is also used in WEO 2023) for example, projects 2050 energy supply being 541 EJ, which is a decrease of 14% compared with the historic 2022 figure of 632 EJ. Meanwhile, in late 2022 world population reached 8 billion and is estimated to increase to 9.8 billion by 2050 – which would mean that the NZE Scenario relies on a reduction in energy supply per capita of well over 40% between 2022 and 2050.
Electrification, especially of transport, is a key means of reducing carbon emissions – for example, running electric vehicles on electricity produced by low-carbon sources will reduce the demand for fossil-fuelled combustion engines. Compared with the projected electricity generation in 2050 in the STEPS (53,985 TWh), electricity generation for that year in the NZE Scenario is 42% higher (76,838 TWh). At the same time, the use of unabated fossil fuels in electricity generation is projected to decrease.
Combining all these factors, net zero emissions by 2050 is unlikely to be achieved if the proportion of nuclear generation in the electricity mix is reduced. However, the NZE Scenario in WEO 2023 projects the proportion of nuclear generation to decrease from 10.0% of total generation in 2020 to 7.8% in 2050.
Under the NZE Scenario, installed nuclear capacity would be 916 GWe in 2050, providing 6015 TWh of electricity. This implies an average capacity factor of 75.0% (compared with the 2020 nuclear electricity capacity factor of 73.5%) – which indicates that the IEA affords little scope for nuclear generation to provide any other form of energy (e.g. industrial heat) than electricity in 2050.
Net Zero Nuclear initiative
In order to maintain the 10.0% share of total electricity generation that was achieved in 2020, nuclear generation would have to account for 7690 TWh of the 76,838 TWh total generation in 2050 that is projected in the NZE Scenario. Assuming the same average capacity factor used in the NZE Scenario (75.0%), this would require 1170 GWe installed nuclear capacity, or 2.8 times the amount of nuclear capacity in 2020.
Global nuclear capacity factors have generally been above 80% since around 2000. However, nuclear energy is likely to be used in several other applications beyond electricity production – e.g. hydrogen production and process heat – due to its reliability, scale and environmental advantages.
The more energy from nuclear that is used in non-electric applications, the lower the overall electricity capacity factor. Therefore, while plant performance is improving, it is likely that nuclear worldwide capacity factors (for electricity production) may decline over the coming decades. In order to maintain its current proportion of electricity generation, at least a tripling of nuclear capacity (compared to 2020 levels) would be needed.
In late 2023 the Net Zero Nuclear initiative was launched, with the aim of tripling nuclear capacity by 2050 in order to achieve climate targets. Given the recent stagnation of the sector, this level of expansion is extremely ambitious. However, this goal would only maintain nuclear’s current contribution to electricity generation. If net zero carbon emissions are to be achieved over this timescale, then the nuclear sector would need to expand even more.