Realising the full potential of expanding solar PV and wind requires proactive integration strategies. Between 2018 and 2023, solar PV and wind capacity more than doubled, while their share of electricity generation almost doubled. Governments are positioning these sources as key pillars for decarbonising the energy sector, and capacity is expected to continue expanding at speed towards 2030, driven by a supportive policy environment and recent cost reductions in solar PV and wind. The COP28 pledge to triple global renewable capacity by 2030 suggests growth could accelerate even more than anticipated, requiring intensified efforts and investments to meet this ambitious target.

Maximising the benefits from increased solar PV and wind capacity requires effective integration into power systems. While power systems have always managed demand variability, variable renewable energy (VRE) such as wind and solar PV introduces supply variability depending on the weather. This variability will require increasing the flexibility of the entire power system, by leveraging dispatchable generation, grid enhancements, increased storage and demand response. Successful integration maximises the amount of energy that can be sourced securely and affordably, minimises costly system stability measures, and reduces dependency on fossil fuels.

Delaying the implementation of measures to support integration could jeopardise up to 15% of solar PV and wind power generation in 2030 and would likely result in up to a 20% smaller reduction of carbon dioxide (CO₂) emissions in the power sector. Should integration measures fail to be implemented in line with a scenario aligned with national climate targets, up to 2 000 terawatt-hours (TWh) of global VRE generation would be at risk by 2030, endangering achieving national energy and climate pledges. This potential loss – equivalent to the combined VRE output of China and the United States in 2023 – stems from possible increases in technical and economic curtailment, as well as potential project connection delays. Consequently, the share of solar PV and wind in the global electricity mix in 2030 would reach 30%, lower than the 35% in the case where integration measures are implemented on time. If this decrease is compensated by increased reliance on fossil fuels, it could lead to up to a 20% smaller reduction of CO₂ emissions in the power sector. 

Governments must strategically support targeted integration measures, but guidance is needed on which to prioritise at different stages. Integration of VRE has been a key research focus for many years in leading markets, resulting in the proposal of numerous technological, policy and operational measures. Despite this extensive research, identifying specific priority measures for implementation remains challenging. This report aims to support policy makers on this issue by presenting an update of the IEA’s phases of VRE integration framework, originally developed in 2017 and subsequently refined with the Clean Energy Ministerial Initiative, 21^st Century Power Partnership.

This framework identifies six phases1 of increasing system impacts from solar PV and wind generation, each with corresponding challenges and solutions. By mapping a system to its current phase, the framework helps identify priority integration measures and facilitates the sharing of experiences across systems in similar circumstances.

The IEA's stocktake reveals proven strategies and concrete measures for successful VRE integration. This report presents a first-ever comprehensive stocktake of integration measures implemented across 50 power systems worldwide, covering nearly 90% of global solar PV and wind generation. The analysis identifies a core set of measures universally adopted by systems in Phase 2 of VRE integration and higher. These serve as a guide for governments to identify and implement proven, effective integration approaches. Additionally, the stocktake provides insight into the measures adopted in systems at the forefront of VRE integration, offering a guide for creating forward-looking strategies.

Most of the growth in VRE generation will occur in systems at low phases of VRE integration (Phases 1 to 3). In a scenario in which countries meet their climate and energy commitments in full and on time, nearly two-thirds of additional solar PV and wind generation in 2030 compared to 2022 is projected to occur in systems at low phases of VRE integration. These systems are primarily located in emerging market and developing economies (EMDEs), including India and Brazil, along with others in the Middle East, Asia, Africa and Latin America. The remaining third of VRE generation growth would take place in energy systems at high phases of integration, many of which are in advanced economies.

Measures based on progressive and targeted adjustments can integrate most new capacity in lower-phase systems. Systems in early integration phases experience relatively low impacts as solar PV and wind generation increase, with most challenges addressable through straightforward modifications to existing assets or operational improvements that increase flexibility. Our stocktake, which identified core integration measures implemented in all of the 40 systems in Phase 2 or higher, revealed a common characteristic: they could be implemented in a targeted and progressive manner. These measures include optimising dispatch processes and improved forecasting, soliciting higher flexibility and system services from both conventional and VRE power plants, enabling industrial demand response and enhancing grid infrastructure. The key advantage of these measures lies in their adaptability, as they do not require complete implementation or sweeping transformations of the power system, regulatory frameworks or market structures. Instead, they provide a flexible approach that can be tailored to address specific challenges as they arise, facilitating a cost-effective and scalable integration process that evolves alongside the changing needs of the power system.

Integration challenges should not be seen as a significant barrier for expanding VRE capacity in systems at low phases of integration. The relatively low system-level impacts of VRE in low-phase systems, coupled with the availability of cost-effective, progressively implementable integration measures, should alleviate concerns about integration challenges for countries with low VRE penetration. By implementing the core integration measures we identified in tandem with VRE deployment, systems with currently limited VRE capacity can significantly accelerate their clean energy ambitions. This strategic approach is crucial for maximising the benefits of VRE technologies, including their positive impacts on decarbonisation, delivering affordable energy to consumers and reducing dependency on fossil fuels.

Some frontrunner power systems today are effectively managing high levels of VRE. Systems such as those in Denmark, Ireland, South Australia and Spain have reached Phase 4 or higher, integrating from 35 up to 75% of VRE in their annual generation, depending on the system. At these penetration levels, challenges in stability and flexibility across all timeframes become more acute. These systems often see VRE cover most of their generation for over a day, necessitating innovative solutions in terms of operating, planning, and financing their power system. Their experiences provide valuable insights for other systems around the world aiming to accelerate VRE integration.

Existing technologies are successfully helping to tackle the challenges associated with integrating high shares of VRE. Most technological solutions addressing emerging challenges – namely, a higher focus on stability and a growing need for flexibility across all timeframes – are either mature or commercially available. The key to their successful rollout often lies in appropriate policy and regulatory action rather than new technological breakthroughs. For many systems, reaching Phase 4 or even 5 depends mainly on effective deployment of existing technologies rather than developing new ones. While for Phase 6, viable technologies exist but their implementation at a large scale remains limited, requiring additional testing or economic incentives for deployment.

Achieving this level of integration requires a paradigm shift in system operation, planning, and financing. Integrating high shares of VRE requires rethinking the traditional way in which power systems are operated, planned, and financed. Essential elements include modernising system operation practices, improved strategic planning, and overhauling regulatory frameworks. Market design must evolve as well to accommodate the unique characteristics of solar and wind-dominated grids, new technologies, and the new role of conventional generation as the provider of essential system services rather than energy. This includes developing new methods for procuring and rewarding necessary system services, ensuring they are maintained and evolved as needed.

While significant progress has been made by frontrunner systems, not all answers exist today for future very high VRE penetration levels. The continued and accelerated VRE growth in the coming decade will likely unveil new integration challenges. These may come from frontrunner systems reaching unprecedented levels of VRE or from systems with unique local conditions that require innovative solutions. Many additional systems – including those in Australia, Japan, Italy and Brazil – are expected to reach Phase 4 or higher by 2030. For these systems, an ongoing focus on developing integration measures – coupled with global sharing of effective policies, regulatory frameworks, and market design elements – will be crucial in supporting a secure energy transition.

Some key issues for power systems with very high VRE penetration remain unresolved. These topics include addressing seasonal variability concerns, operating systems with very high levels of converter-based resources, ensuring the profitability of new investments amid increasing price volatility, and appropriately remunerating assets that provide flexibility for their system value. Resolving these challenges will require continued innovation, collaboration and commitment from policy makers, technology leaders and researchers worldwide.