A global study finds India to be the most cost-effective country for rooftop solar energy generation, ahead of China, the UK, and the USA. The cost of the maximum PV electricity generation (LCOE) from a given rooftop area in India is the lowest at US$66/MWh, according to the study which is based on data available as of 2018. After India, China (at US$68/MWh) has the lowest cost for attaining the potential energy. The USA ($238/MWh) and the UK ($251/MWh) are among some of the costliest countries.

Even though the LCOE difference between India and China is minimal, rooftop solar PV technology rollout becomes more favorable in India than in China due to greater solar endowment and high yield factor. The average cost of obtaining solar rooftop potential in India would vary between $60 and $85 per megawatt-hour, with the costs being the lowest in Gujarat and Rajasthan, as per the study.

This first-of-its-kind study to assess global energy generation from rooftop solar PV systems has been co-authored by Priyadarshi Shukla, professor at Ahmedabad University and director of its Global Centre for Environment and Energy, Shivika Mittal from Imperial College London, and James Glynn from Columbia University. The team was led by Siddharth Joshi, researcher at MaREI, the SFI Research Centre for Energy, Climate and Marine in University College Cork. Joshi was supported by his colleagues, Professor Brian Ó Gallachóir and Professor Paul Holloway.  

Generation potential

The study also found a global rooftop solar energy generation potential of 27 petawatt-hour per year. Nearly 20% (5 PWh/year) of the global potential is located within the areas with a high population density (>1500 people/km2) due to a corresponding increase in the building stock, with 55% (15 PWh/year) of the potential being dispersed within the low-density areas within the low-density areas (<500 people/km2).  

Among the countries, China (4.3 PWh/year), USA (4.2 PWh/year) and India (1.7 PWh/year) have the highest solar energy generation potential.

In India, Maharashtra (181 terawatt-hour per year) and Uttar Pradesh (168.07 terawatt-hour per year) have the highest solar rooftop potential. 

“Solar energy is generated during daytime coinciding with the time when electricity demand is at its peak. India’s solar rooftop potential of 1.7 petawatt-hour per year is very significant. We would be able to match India’s current electricity demand of 1.3 petawatt-hour per annum if we install efficient solar panels on 40% of the country’s available rooftop area,” said Professor Shukla. 

Methodology

The researchers employed a modeling framework to assess the electricity generation potential of rooftop solar PV systems globally and its associated costs. The authors mapped 130 million km2 of global land surface area to identify 0.2 million km2 of rooftop area using a machine learning algorithm. This rooftop area was then analyzed to document the global electricity generation potential of rooftop solar PV. 

“For the first time, we can analyze the spatial and temporal characteristics of global rooftop photovoltaics with improved accuracy using a combination of big data, machine learning, and GIS. This study can aid in improved representation of RTSPVs in global energy systems,” said Joshi of UCC.

The energy generation potential of rooftop solar panels exceeded the global yearly aggregated energy consumption in 2018. However, its future potential will depend on the development and cost of storage solutions for the generated energy.