World Energy Model

Part of World Energy Outlook

Sustainable Development Scenario

A cleaner and more inclusive energy future

The world is not on track to meet the energy-related components of the Sustainable Development Goals (SDGs). The IEA’s Sustainable Development Scenario (SDS) outlines a major transformation of the global energy system, showing how the world can change course to deliver on the three main energy-related SDGs simultaneously.

Based on existing and announced policies – as described in the IEA Stated Policies Scenario (STEPS) – the world is not on course to achieve the outcomes of the UN SDGs most closely related to energy: to achieve universal access to energy (SDG 7), to reduce the severe health impacts of air pollution (part of SDG 3) and to tackle climate change (SDG 13).

The SDS sets out an ambitious and pragmatic vision of how the global energy sector can evolve in order to achieve these critical energy-related SDGs. It starts with the SDG outcomes and then works back to set out what would be needed to deliver these goals in a realistic and cost-effective way. In the WEO-2020, the Sustainable Development Scenario also integrates the stimulus packages required for a global sustainable recovery from Covid-19. Investments in the 2021-2023 period are therefore aligned with the Sustainable Recovery depicted in the World Energy Outlook Special Report.

The Paris Agreement has an objective of “holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels”. Energy production and use is the largest source of global greenhouse-gas (GHG) emissions, meaning that the energy sector is crucial for achieving this objective.

To achieve the temperature goal, the Paris Agreement calls for emissions to peak as soon as possible and reduce rapidly thereafter, leading to a balance between anthropogenic emissions by sources and removals by sinks (i.e. net-zero emissions) in the second half of this century. These conditions are all met in the SDS.

The SDS holds the temperature rise to below 1.8 °C with a 66% probability without reliance on global net-negative CO2 emissions; this is equivalent to limiting the temperature rise to 1.65 °C with a 50% probability. Global COemissions from the energy sector and industrial processes fall from 35.8 billion tonnes in 2019 to less than 10 billion tonnes by 2050 and are on track to net zero emissions by 2070.

Compare the new SDS 2020 to IPCC scenarios with a  temperature rise in 2100


Source: IAMC 1.5°C Scenario Explorer hosted by IIASA release 1.1,,

The IPCC Special Report on Global Warming of 1.5°C, published in 2018, assessed a large number of scenarios that led to at least a 50% chance of limiting the temperature rise to 1.5 °C. As the figure above makes clear, the SDS trajectory is well within the envelope of these scenarios.

Almost all of these IPCC scenarios (88 out of 90) assume some level of net negative emissions. The Sustainable Development Scenario does not rely on net negative emissions, but if the requisite technologies became available at scale, warming could be further limited. A level of net negative emissions significantly smaller than that used in most scenarios assessed by the IPCC would provide the Sustainable Development Scenario with a 50% probability of limiting the rise in global temperatures to 1.5°C.

Cumulative net-negative CO2 emissions between 2018 and 2100 in 1.5°C scenarios assessed by the IPCC


However, as frequently highlighted in the WEO, there are reasons to limit reliance on early-stage technologies for which future rates of deployment are highly uncertain: that is why the SDS emphasises the importance of early action on reducing emissions.

In the light of concern surrounding negative emissions technologies, it would be possible to construct a scenario that goes further than the Sustainable Development Scenario and delivers a 50% chance of limiting warming to 1.5 °C without any reliance on net-negative emissions. These conditions would require achieving net zero emissions globally by around 2050.

Eliminating the 10 Gt CO2 energy-sector emissions remaining in SDS in 2050 would not amount to a simple extension of the changes to the energy system described in the SDS. The additional changes involved – particularly those surrounding rates of technological change, infrastructure constraints, social acceptance and behavioural changes, and capital stock replacement – would pose challenges that would be very difficult and very expensive to surmount. This is not something that is within the power of the energy sector alone to deliver. Change on a massive scale would be necessary across a very broad front, and would impinge directly on the lives of almost everyone.

The Paris Agreement is also clear that climate change mitigation objectives should be fulfilled in the context of sustainable development and efforts to eradicate poverty. The Sustainable Development Scenario explicitly supports these broader development efforts (in contrast to most other decarbonisation scenarios), in particular through its energy access and cleaner air dimensions.

In the Sustainable Development Scenario, strong policy support and international co-operation are an integral part of national and international recovery plans, and this enables a ramping up of progress on expanding access programmes to achieve universal access to electricity and clean cooking by 2030, despite the near-term slowdown caused by the health crisis and economic downturn.  This scenario requires $40 billion of annual investment between 2021 and 2030 to reach universal access, making full use of decentralised solutions.  Achieving universal access will transform the lives of hundreds of millions, and reduce the severe health impacts of indoor air pollution, overwhelmingly caused by smoke from cooking.

Access to electricity in the Sustainable Development Scenario, 2010-2030


Access to clean cooking in the Sustainable Development Scenario, 2010-2030


Outdoor air pollution is reduced substantially, leading to more than 2 million fewer premature deaths globally in 2050 than projected in the STEPS. Household air pollution also falls sharply, with access to clean cooking contributing to 1 million fewer premature deaths.

Global premature deaths attributable to air pollution by scenario, 2019-2050


There is no trade-off between achieving climate objectives and delivering on energy access and air pollution goals.

Good policy design can exploit synergies between the three parallel objectives of the SDS. Achieving universal access to modern energy only leads to a small increase in CO2 emissions (0.1%), the climate effect of which is more than offset by lower methane emissions due to a reduction in use of traditional biomass cookstoves. Incorporating additional elements of the sustainable development agenda, such as energy and water, or energy and gender, highlight further synergies.

The transition to a low-carbon economy leads to a more efficient energy system that relies less on fuel combustion; this plays a major role in improving air quality, reducing both outdoor and household air pollution. In countries where reducing health impacts of air pollution is an urgent issue, low-carbon measures that reduce the overall quantity of fossil fuels being used – including energy efficiency measures on the demand side, and a shift to renewables on the supply side – are an important part of an action plan to tackle those health-related impacts.

The SDS requires around an increase in overall investment compared to STEPS of around 25% over the period to 2050. This additional investment cost is partially counterbalanced by reduced fuel costs, which mitigates the impact on the energy bills paid by consumers. There is a significant shift in capital spending away from fossil fuels to renewables and other low-carbon sources as well as to electricity.

The largest increase in supply investment comes from renewables-based power, which is on average double today’s level between 2020 and 2050. This is supported by additional spending on electricity grids and battery storage, in order to ensure reliable electricity supply.

The other major shift in spending is towards the demand side, to take advantage of the huge potential for energy efficiency. This means additional spending on more efficient buildings, industrial processes and transport, as well as new demand-side infrastructure, e.g. for EV recharging.

The investment needed to achieve universal energy access amounts to some $40 billion per year between 2021 and 2030, the lion’s share of it for electricity access. This is double the annual investment in STEPS, but still less than 2% of the total energy sector investment in SDS. Required investment was higher in WEO-2019, at $45 billion per year. The drop is due to huge progress in India and to the rapid decline of solar price.

Annual average energy investment in fuels in the Sustainable Development Scenario, 2015-2030


Annual average energy investment in End-use in the Sustainable Development Scenario, 2015-2030


Annual average energy investment in power in the Sustainable Development Scenario


The World Energy Outlook introduced a detailed energy transition scenario in 2009 – then called the 450 Scenario. The scenario got its name from 450 parts per million (ppm), the CO2 concentration that was seen at that time to be consistent with a 50% likelihood of keeping average global temperature rise below 2 °C (assuming that net zero emissions were reached in 2100).

Since then the global goalposts have shifted, technological progress has been uneven, and emissions have continued to grow. The SDS looks very different from the 450 Scenario proposed in the WEO-2009, for three main reasons:

  • A tougher starting point. Energy-related CO2 emissions in 2018 reached a record high of 33 billion tonnes (Gt) - a huge 2.5 Gt above the level what was set out in the 450 Scenario for 2018. Not only does this mean that emissions in the SDS must fall to a greater extent than in the 450 Scenario, but there is also a larger carbon-intensive capital stock that must be managed.
  • Higher ambition. The 450 Scenario was compatible with reaching net-zero CO2 emissions towards the end of the century whereas SDS aims to achieve net-zero CO2 emissions in 2070. The emissions trajectory of SDS, combined with the higher starting point, means that emissions decline by 730 million tonnes (Mt) on average each year compared with a 400 Mt average annual decline in the 450 Scenario.
  • Uneven technological progress. The SDS relies much more on solar and wind in the power sector, and less on carbon capture, utilisation and storage (CCUS) and nuclear than the 450 Scenario. For example, in 2030 in the 450 Scenario from the WEO-2009, nuclear and CCUS generated around 7 100 TWh of electricity while wind and solar PV generated 3 600 TWh. In the SDS these figures are broadly reversed with nuclear and CCUS generating 3 900 TWh, and wind and solar PV generating 8 100 TWh.