The global energy transition is gaining momentum, and rooftop solar (RTS) systems are playing a significant role in addressing the world’s growing energy demand. With projections suggesting a 75% increase in global electricity demand by 2050 (IEA 2022), geopolitical disruptions, such as the Russia-Ukraine conflict and the COVID-19 pandemic recovery, have further underscored the need for a shift toward renewable energy (RE) sources. Solar photovoltaics (PV) in particular, including distributed solar technologies, are well-positioned to contribute to these global efforts.
Introduction: Evolution and growth of solar PV
Solar PV has evolved significantly from being dominated by rooftop installations in the early 2000s to seeing increased utility-scale deployments over the last decade. During the early years, rooftop solar accounted for over 90% of installed capacity, driven by the residential sector. However, between 2021 and 2022, utility-scale installations began declining due to supply chain disruptions and higher costs, leading to a resurgence of RTS among residential, commercial, and industrial consumers.
In 2023, the total installed capacity of RTS reached 636 GW globally, a 67% surge from the previous year. The commercial and industrial (C&I) sectors lead RTS installations, which are expected to grow further by 268 GW by 2027 (SolarPower Europe 2024). China remains the largest player in RTS, with 225 GW of installed capacity, followed by Germany and the United States. Looking ahead, the International Energy Agency (IEA) forecasts 100 million RTS installations in the residential sector by 2030, expanding to 240 million by 2050.
China: A Rooftop Solar Pioneer
China leads the global rooftop solar market with around 37% of its 609 GW total solar capacity installed as RTS. China aims to reach 1,200 GW of solar and wind energy by 2030. Its journey began with initiatives like the Golden Sun Programme, which promoted both distributed and utility-scale solar systems. Although challenges emerged due to policy implementation gaps, the programme drove substantial growth in solar capacity.
Furthering its commitment, China launched the Solar Energy for Poverty Alleviation Programme in 2014, which aimed to support rural villages by installing 10 GW of distributed solar. By 2020, 26 GW was installed, benefiting 4.18 million households. In 2021, the Whole County PV Programme was introduced to accelerate RTS deployment by targeting government buildings, public spaces, and rural homes.
China’s future outlook includes significant investments in grid modernization and energy storage, with CNY 500 billion (USD 70 billion) allocated for infrastructure improvements to support solar grid integration.
Germany: Putting Renewable Energy First
Germany’s renewable energy policies have propelled the nation’s RTS growth. With a technical potential of 409 GW, rooftop solar now accounts for 53 GW of installed capacity in Germany. The country’s target is to achieve 80% renewable energy in its gross electricity consumption by 2030, deploying 215 GW of solar, including 11 GW annually in RTS.
Key milestones in Germany’s journey include the 100,000 Roofs Programme and the Renewable Energy Sources Act (EEG), which offered attractive feed-in tariffs (FiTs) to promote RTS adoption. Over the years, Germany has reduced FiTs, yet innovations like energy cooperatives, landlord-to-tenant models, and balcony solar systems have driven consumer engagement.
Looking forward, Germany’s 2023 photovoltaic strategy is expected to enhance RTS growth through streamlined grid connection processes, higher FiTs for commercial RTS, and a focus on small-scale energy storage.
United States: Advancing a clean energy economy
The United States boasts one of the world’s largest RTS markets, with around 47 GW of installed capacity as of 2023. California leads in RTS, contributing 16 GW. Federal tax credits, such as the solar investment tax credit (ITC), have been essential drivers for adoption. Under the Inflation Reduction Act of 2022, tax credits were extended, providing a 30% reduction in installation costs.
State-level regulations also play a key role, with net energy metering (NEM) and net billing systems compensating consumers for excess electricity generation. The Solar Energy Technologies Office (SETO) has introduced several programs to accelerate RTS deployment, including SolSmart and SolarAPP+, which streamline permitting processes and reduce project timelines.
The US is also focused on equity in solar access. The EPA’s Solar for All program, introduced in 2023, aims to close the gap in solar energy access, particularly for low-income households. With these initiatives, the US is expected to maintain its growth trajectory, with rooftop solar at the heart of its clean energy future.
Japan: A consistent performer
Japan has long been a leader in distributed solar deployment, with RTS contributing 39% to its total renewable capacity. Japan’s feed-in tariff scheme, introduced after the 2011 Fukushima nuclear disaster, spurred a record 10.9 GW installation in 2015. Although FiTs were phased out by 2019, Japan transitioned to a feed-in premium system to continue incentivizing solar adoption.
Looking ahead, Japan aims to install 147 GW of PV capacity by 2030, with a focus on integrating rooftop solar into new buildings and enhancing consumer access to energy management tools.
Australia: Rooftop solar success story
Australia leads the world in per capita rooftop solar, with one in three homes equipped with RTS systems. Its 22.2 GW of installed capacity accounts for 30% of the country’s renewable energy mix. State-level FiTs and a high retail electricity tariff have made RTS highly attractive to Australian consumers.
Australia’s Renewable Energy Target (RET) mandates have also played a critical role in driving adoption. Looking forward, Australia’s Integrated System Plan projects 36 GW of RTS by 2030 and 86 GW by 2050, ensuring rooftop solar remains a key driver in its energy transition.
Comparative analysis
Across the selected countries, several common themes have emerged. Policy and regulatory support, especially through FiTs and tax credits, have been critical in accelerating RTS adoption. Innovative business models, such as community solar in the US and Germany’s energy cooperatives, have expanded consumer access to rooftop solar. Additionally, technological advancements have significantly reduced the costs of PV modules, making solar energy economically viable for both residential and commercial consumers.
Recommendations for scaling rooftop solar
Drawing from the lessons of leading economies, several key recommendations emerge for countries seeking to scale up their RTS deployment:
Consumer engagement: Countries should invest in consumer awareness campaigns to encourage rooftop solar adoption. Streamlining communication through national online platforms can also aid in information dissemination.
Targeted incentives: Governments should introduce phased-down incentive mechanisms like FiTs, combined with low-interest financing to ensure solar’s economic viability.
Regulatory frameworks: Policies such as net metering and net billing should be introduced to incentivize consumers, with special attention to simplifying procedures for installations.
Ecosystem development: Building an enabling ecosystem requires local capacity-building initiatives and streamlined permitting processes. Vendor rating programs, such as those in India and Australia, also improve consumer trust.
Conclusion
Rooftop solar energy presents a transformative opportunity for countries worldwide to transition to cleaner, more resilient energy systems. By adopting innovative policy mechanisms and leveraging best practices from leading economies, nations can unlock the full potential of rooftop solar, contributing to global energy security and sustainability goals.
This article is based on the report “Global Perspectives on Rooftop Solar Energy: A Deep Dive on How Leading Economies Advance Rooftop Solar Energy Adoption,” authored by Bhawna Tyagi, Debanjan Bagui, Arohi Patil, Kumaresh Ramesh, Aryadipta Jena, and Megha Chaudhary, and published by the Council on Energy, Environment and Water (CEEW).