The Environmental Case for Rooftop Solar Energy
Protecting California’s Climate and Land

Executive Summary

California has long been a global leader in environmental protection. California’s pioneering actions to reduce air pollution, safeguard natural areas, and protect vulnerable species have set a high standard for the United States and beyond.

Today, California faces its biggest environmental challenge: climate change. Over the next several decades, California will need to repower its economy with clean, renewable energy – and do so with as little impact as possible on wildlife and wild places.

Rooftop solar power is a key tool in the fight against climate change. Solar energy on homes, schools, farms and other buildings can be deployed at the speed and scale required to meet the climate crisis, and it can do so while contributing to a resilient, ecologically vibrant future for California.

Installing more rooftop solar can increase renewable electricity generation while protecting the state’s open spaces and helping to make communities more resilient to global warming-related disruptions to the power grid. To accelerate the transition to a 100% clean energy system while protecting our environment, California should adopt policies that continue the growth of solar power on homes, businesses, schools, farms and other buildings.

Rooftop solar is critical to helping California meet its climate goals. California has set out to achieve net-zero greenhouse gas emissions by 2045 and also to obtain 100% of retail electricity sales from renewable and zero-carbon sources by 2045.1

  • State officials assume that California will nearly quadruple its current rooftop solar capacity – from 10.5 gigawatts to 39 gigawatts (GW) – as it seeks to reach its 2045 climate and clean energy goals.2 This is in addition to even larger amounts of utility-scale solar.3
  • California has extensive potential for generating more electricity from rooftop solar installations (see Figure ES-1). A 2016 analysis by the National Renewable Energy Laboratory found that the state has the technical potential to meet more than three quarters of its electricity demand with rooftop solar energy.4

Figure ES-1. Rooftop solar has plenty of room to grow in California5

Rooftop solar can be installed more quickly than any other electricity generating source, enabling California to respond at the speed and scale necessary to address the climate crisis.

  • A residential rooftop solar project is typically installed within three months of inception, and commercial rooftop installations typically take between two and four months.6
  • Avoiding climate emissions today can help limit the extent of warming that the state and the rest of the world will experience.7 Pollution reductions today provide greater benefit than the same emission reductions a year or 10 years in the future.

Rooftop solar energy does not change existing land uses and can help California protect agricultural land, fragile habitats and natural areas. These places are disrupted by utility-scale solar projects, which California will need to meet its climate and clean energy goals. However, by tapping rooftop solar opportunities, California can reduce the total amount of utility-scale solar needed and help to protect natural areas. State regulators calculate an additional 28.5 GW of rooftop solar will be built by 2045.8 By using this amount of rooftop solar instead of utility-scale solar, California can maintain existing land uses on more than 148,000 acres of land – an area about half the size of the City of Los Angeles.9

  • In October 2020, Governor Gavin Newsom issued an executive order committing California to protecting 30% of its natural land and water areas by 2030, up from the 22% that is protected currently.10 Rooftop solar can help minimize conflicts between the state’s conservation and clean energy goals.
  • Rooftop solar is built on already developed land. By reducing the need for utility-scale facilities, it can reduce the impacts of electricity generation on the natural environment that California is seeking to protect.
  • An additional land conservation benefit of rooftop solar is that it produces electricity close to where it is consumed. As a result, it reduces the need for new transmission infrastructure, which can damage or destroy farmland and ecosystems.

Climate change will have disruptive effects on California, even if we move quickly to curb emissions. Rooftop solar energy and batteries can help California communities be more resilient to climate-related disruptions to the electricity grid. When paired with energy storage, solar on homes, businesses, schools and other locations can help buildings or communities keep the power on during emergencies.

  • Californians have experienced numerous climate-related blackouts in recent years, both during pre-emptive power shut-offs intended to prevent transmission lines from sparking fires in drought-stressed forests and during unprecedented heat waves when electricity demand outstripped supply.
  • If a rooftop solar system is connected to battery storage, the energy the solar panels generate can be used to power a home even when the rest of the grid loses power.11 This can keep food cold, operate well-water pumps, and provide cooling and lighting.

To ensure the installation of enough solar on homes, businesses, schools, farms and other buildings to meet its climate and clean energy goals, California needs a range of policies supporting rooftop solar generation, including.

  • As California updates its net energy metering policy, which allows the owners of rooftop solar panels to be compensated for the electricity they provide to the power grid, it should ensure that the revised policy provides sufficient support to allow the undiminished growth of rooftop solar. Slower growth of distributed solar creates a risk that the state will not meet its climate and clean energy targets.
  • California should seek to accelerate solar energy adoption on affordable and rental housing, including by allowing financing through utility bills and ensuring solar owners who pay reduced rates are fully compensated for the power they provide to the grid.
  • In addition, cities and counties should establish online automated permitting systems for small onsite solar projects, using systems like SolarAPP+ developed by the National Renewable Energy Laboratory.

 

 


  1. California Energy Commission et al., 2021 SB 100 Joint Agency Report, 15 March 2021, p. 24 and 26, downloaded at https://www.energy.ca.gov/sb100; California Public Utilities Code § 454.53 (8 November 2018); Emissions goal executive order: Executive Department of the State of California, Executive Order B-55-18 to Achieve Carbon Neutrality, 10 September 2018, archived at http://web.archive.org/web/20210416215514/https://www.ca.gov/archive/gov39/wp-content/uploads/2018/09/9.10.18-Executive-Order.pdf.↩︎
  2. 39 GW: California Energy Commission et al., 2021 SB 100 Joint Agency Report, 15 March 2021, p. 104, downloaded at https://www.energy.ca.gov/sb100; 10.5 GW: California Distributed Generation Statistics, California Leads the Nation in Distributed Generation, accessed 25 May 2021 at https://www.californiadgstats.ca.gov/.↩︎
  3. California Energy Commission et al., 2021 SB 100 Joint Agency Report, 15 March 2021, p. 76, 84, 85, 87, 88, 91, 95 and 100, downloaded at https://www.energy.ca.gov/sb100.↩︎
  4. Technical potential: Pieter Gagnon et al., National Renewable Energy Laboratory, Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment, January 2016, p. 35, archived at http://web.archive.org/web/20210320150001/https://www.nrel.gov/docs/fy16osti/65298.pdf; California’s 2019 retail sales of electricity totaled 250.38 TWh: U.S. Energy Information Administration, State Electricity Profiles, 2 November 2020, archived at https://web.archive.org/web/20210603192740/https://www.eia.gov/electricity/state/.↩︎
  5. 10.5 GW: California Distributed Generation Statistics, California Leads the Nation in Distributed Generation, accessed 25 May 2021 at https://www.californiadgstats.ca.gov/; 2045 modeled capacity: California Energy Commission et al., 2021 SB 100 Joint Agency Report, 15 March 2021, p. 104, downloaded at https://www.energy.ca.gov/sb100; Technical potential: Pieter Gagnon et al., Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment, National Renewable Energy Laboratory, January 2016, p. 35, archived at http://web.archive.org/web/20210320150001/https://www.nrel.gov/docs/fy16osti/65298.pdf.↩︎
  6. Kerry Thoubberon, “How long does it take to install solar panels?,” Energy Sage, 2 January 2019, archived at http://web.archive.org/web/20201027215009/https://news.energysage.com/how-long-does-it-take-to-install-solar-panels/; Yellow Lite, How Long Does it Take to Install Solar, From Start to Finish?, 27 May 2016, archived at http://web.archive.org/web/20200808063209/https://www.yellowlite.com/blog/post/how-long-does-it-take-to-install-solar-from-start-to-finish/; Yujing Lin, “How long do commercial solar projects take?,” Energy Link, 14 February 2019, archived at http://web.archive.org/web/20200930085004/https://goenergylink.com/blog/how-long-do-commercial-solar-projects-take/.↩︎
  7. A recent study shows that stringent, rapid emission reduction measures taken today have climate benefits not just long-term but in the near future, meaning that the faster we can reduce emissions the more stable we can keep the climate. In other words, a unit of avoided pollution today counts not just for long-term emissions reductions or long-term warming limits, but for short term benefits as well, and so is more valuable than the same unit of avoided pollution a decade or two decades in the future. See: Christine M. McKenna et al., “Stringent mitigation substantially reduces risk of unprecedented near-term warming rates,” Nature Climate Change, volume 11: p. 126-131, doi: 10.1038/s41558-020-00957-9, 7 December 2020.↩︎
  8. See note 2; 28.5 GW is the difference between current capacity (10.5 GW) and projected 2045 capacity (39 GW).↩︎
  9. See the methodology of this report for calculation of land area that could be conserved or kept in current use. Area of Los Angeles converted from square miles to acres: U.S. Census Bureau, QuickFacts: Los Angeles City, California, accessed 27 April 2021 at https://www.census.gov/quickfacts/losangelescitycalifornia.↩︎
  10. Gavin Newsom, Executive Order N-82-20, 7 October 2020, archived at http://web.archive.org/web/20201121082807/https://www.gov.ca.gov/wp-content/uploads/2020/10/10.07.2020-EO-N-82-20-.pdf; Associated Press, “Newsom calls for protecting 30% of state land in league with international effort,” LA Times, 7 October 2020, archived at https://web.archive.org/web/20210414153943/https://www.latimes.com/environment/story/2020-10-07/california-newsom-state-land-protections.↩︎
  11. SolarHub Energy, How To Use Solar Panels During Power Outage?, archived at http://web.archive.org/web/20210123071114/https://www.solyndra.com/how-to-use-solar-panels-during-power-outage/.↩︎