Rooftop solar refers to solar power plants that are installed typically on residential, commercial or industrial rooftops.
In the early days of solar power, rooftop solar dominated over utility solar power plants. The situation reversed starting around 2010 with utility solar power plants contributing to about two thirds of total global solar PV installations for the 2010-2020 period. In absolute numbers, rooftop solar installations globally are still significant, about 40 GW per annum.
Rooftop solar power plants represent a fairly mature technology in themselves. However, there are still many innovations happening around inverters and batteries used for these power plants. In addition, regulatory systems for rooftop solar and its integration with the grid are still evolving in many parts of the world.
Rooftop solar power plants can be installed in most parts of the world, including in regions that have only moderate amounts of sunlight.
The key advantages with rooftop solar are its ease of installation, operations and the ability to just plug it into the existing electrical infrastructure in a residence or commercial building. The key challenge for rooftop solar power is its intermittency, necessitating the use of batteries for those who wish to rely on solar power for a substantial portion of the day. In addition, for many industrial and commercial segments with large power requirements that have limited rooftop areas, rooftop solar can provide only a portion of their total electricity requirements - in some cases, this could be less than 10%.
For the 2020-2030 period, innovations in rooftop solar can be expected in the increasing use of digital tools (especially AI & IoT), business models (subscription-based, OPEX/lease models), mounting structures and better roof integrations, use of distributed solar in microgrids, and virtual rooftop solar power plants.
The decarbonization potential for a kW of rooftop solar PV is in theory the same as what it is for large, utility scale solar PV power plants. In practice, rooftop solar power plants could have a slightly higher decarbonization potential as the power generated is consumed at the same location in most cases, eliminating transmission and distribution losses. In many cases, rooftop solar can also reduce the amount of diesel used as a backup power when the grid is down.
About 250 GW of rooftop solar was installed worldwide by the end of 2020. While utility scale solar power plants will dominate capacity additions during the 2020-2030 period, IEA expects rooftop and distributed solar capacity additions to be in the 60-65 GW range for the 2019-2024 period. Assuming conservatively that this will be the trend until 2030, there could be a cumulative 850 GW of rooftop solar PV capacity worldwide by the end of 2030.
850 GW of solar PV would save about 500 million tons of CO2 emissions per year, when compared to power from conventional power sources.
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