IEA: Net Zero Emissions by 2050 - Acting now to limit overshoot

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2. Energy pathways in the NZE Scenario

Please note: this is quoted from a Creative Commons source:

IEA (2025), World Energy Outlook 2025, IEA, Paris https://www.iea.org/reports/world-energy-outlook-2025, Licence: CC BY 4.0 (report); CC BY NC SA 4.0 (Annex A)

7.3 Energy pathways in the NZE Scenario
The NZE Scenario illustrates a possible global path to the goal of net zero emissions by 2050. Each country will have its own pathway, depending on their circumstances. The energy transition set out in the NZE Scenario has four main pillars: deployment of low-emissions sources of electricity and electrification to reduce emissions in end-uses; improvements in energy efficiency; use of low-emissions fuels such as hydrogen, biofuels, and CCUS; and reductions in methane emissions. These strategies rapidly reduce emissions and drive a demand-led transition away from fossil fuels in this scenario.

7.3.1 Clean electrification
Today, the power sector accounts for about 40% of global energy-related emissions. Shifting electricity generation to low-emissions sources and increasing the deployment of low-emissions electricity in existing and new end-uses are central to the NZE Scenario: these strategies give rise to around two-thirds of the emissions reductions to 2035 (Figure 7.12). In the NZE Scenario, low-emissions sources provide nearly all electricity generation by 2040, while electricity increases its share in total final consumption to around 40% by 2040 and 55% by 2050. The expanding role of electricity in total final consumption and the increase in electricity supply from variable renewable sources underline the importance of electricity security in the NZE Scenario.



Generating electricity with low-emissions sources
Low-emissions sources of electricity – renewables, nuclear, fossil fuels with CCUS, hydrogen and ammonia – accounted for just over 40% of global electricity generation in 2024, up from around 30% a decade ago. Renewables were responsible for 32% of power generation worldwide, and nuclear for around 9%: there was also a very small contribution of less than 0.003% from fossil fuels equipped with CCUS.

Global installed capacity of renewables triples to 2030 from a 2022 baseline in the NZE Scenario, building on the strong momentum already seen in the power sector, and meeting the goal set at COP28 in 2023 (Figure 7.13). As a result, renewables expand from around one-third of total generation today to around three-quarters by 2035. Achieving this while maintaining electricity security means ensuring that investment in electricity system flexibility keeps pace. Having surged by over 80% in 2024, the installed capacity of stationary batteries increases 17-fold to 2035, average of 30% per year, reaching almost 2 900 gigawatts (GW) in capacity terms and more than 8 400 gigawatt-hours (GWh) in energy terms. In the NZE Scenario, investment surges in grid infrastructure, and around 30 million kilometres (km) of new transmission and distribution lines are added by 2035.

As variable renewables such as solar PV and wind account for a rising share of generation, dispatchable capacity plays a critical role to ensure electricity security. Long lead-times for nuclear limits its role in the near term, but installed nuclear capacity in the NZE Scenario increases 70% by 2035 from the current level, and by 2050 it is two-and-a-half times higher. By the 2030s, the nuclear industry delivers annual additions of around 40 GW per year (Box 7.3). Hydropower capacity also expands strongly, with generation increasing more than 1.5-times by 2050. Unabated fossil fuel plants are operated increasingly for flexibility and capacity adequacy, and consequently their installed capacity falls more slowly than their output across the Outlook period. Fossil fuel plants equipped with CCUS and plants fired with hydrogen or ammonia are also deployed, providing additional low-emissions dispatchable capacity.

Box 7.3 ⊳ What would it take to meet the pledge of tripling installed nuclear capacity?
At the COP28 in December 2023, more than 20 countries, representing 70% of current installed nuclear capacity, pledged to triple global nuclear power capacity by 2050. Six additional countries signed the pledge at the COP29 in 2024. If fully realised, this commitment would increase global nuclear capacity from 413 GW in 2020 to 1 240 GW by mid-century, which would exceed the level in the NZE Scenario by 160 GW.

Reaching the tripling target by 2050 would require immediate efforts to scale up the nuclear industry in the 2020s to accelerate deployment in the 2030s and beyond, with annual deployment rates rising quickly in the 2030s to around 40 GW and being maintained throughout that decade and the 2040s. According to our analysis, this would lead to levels of global nuclear capacity additions never achieved before (Figure 7.14). This expansion would support a wide range of applications. Beyond its traditional role in the power sector, nuclear energy could contribute to water desalination and to low-emissions hydrogen production, for example. In the NZE Scenario, the pace of nuclear capacity additions is expected to slow after the mid-2030s, in line with other low-emissions technologies, as most electricity systems become largely decarbonised by then: as a result, capacity rises 2.5-times from the current level rather than tripling.



Achieving this tripling of nuclear capacity would require a significant increase in investment. Annual investment spending would need to rise from over USD 70 billion today to a peak of about USD 210 billion around 2035 before plateauing at around USD 160 billion through the 2040s. Investment would need to be on average 50% higher throughout the 2040s than in the NZE Scenario, resulting in an additional USD 900 billion of spending by 2050. This scaling up would be heavily dependent on robust supply chains, skilled labour and long-term policy support.

The United States could play a central role in this global effort. An Executive Order issued in May 2025 to reform the US Nuclear Regulatory Commission aims to revitalise the domestic nuclear industry and sets a goal of adding 300 GW of new capacity by 2050. It is reinforced by the One Big Beautiful Bill Act, which makes continued tax credits available to the nuclear industry. Countries in the European Union, Middle East, Africa, East Asia and North and Central America are also showing renewed interest in nuclear power as part of their decarbonisation strategies.