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The Understand Energy Learning Hub is a cross-campus effort of the Precourt Institute for Energy.

Solar Energy

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Fast Facts About
Solar Energy

Principal Energy Uses: Daylight, Electricity, Heat
Forms of Energy: Thermal, Radiant

Solar energy is radiant energy from the sun—a fully renewable energy resource. We use the solar resource to provide daylight, electricity, and heat in four ways (in order of prevalence):

  1. Indirect: Our primary use of the sun’s energy is for free light and warmth (not counted in the data below but important for energy efficiency)
  2. Solar PV: Converting photons (light) into electricity through photovoltaics (PV), also known as solar panels
  3. Direct (solar thermal heat): Using the sun to heat water and buildings (hot water, warm pools, space heating/cooling)
  4. Solar Thermal Power (CSP): Concentrating sunlight to produce high-temperature heat to generate electricity, sometimes called concentrating solar power (CSP)

Solar PV is the fastest-growing electricity resource in the world. It is fully renewable with few environmental impacts, and the cheapest source of electricity in many countries.


Energy Mix

2% of world 🌎
(#7 resource)
1% of US 🇺🇸
(#8 resource)

Electricity Generation

5% of world 🌎
(#6 resource)
3% of US 🇺🇸
(#6 resource)

Global Solar Use

Solar PV 74%
Solar thermal heat 25%
CSP 1%

Global Solar PV

Most Installed Capacity

China 37% 🇨🇳
of global installed capacity

Most Generation

China 33% 🇨🇳
of global solar electricity

Highest Penetration

Chile 16% 🇨🇱
of country’s electricity comes from solar

Change in Global Solar PV Electricity Generation

⬆ 197%

US Solar PV

Most Installed Capacity

California 27%
of US installed capacity

Most Generation

California 29%
of US solar electricity

Highest Penetration

California 27%
of state's electricity comes from solar

Global Solar Thermal Heat

Most Installed Capacity

China 73% 🇨🇳
of global installed capacity

(US has 2.5%)

China’s main use is for heating buildings and water, while the main use in the US is for heating swimming pools

Change in Global Solar Thermal Heat Capacity

⬆ 15%

Global Solar Thermal Power (CSP)

Most Installed Capacity

Spain 37% 🇪🇸
of global installed capacity

(US has 21%, 64% of which is in California)

Change in Global CSP Capacity

⬆ 29%

Costs of US Solar PV

Costs increase as size of installation falls:

  1. Utility scale: largest scale, unsubsidized LCOE* = $24 - $96
  2. Community, commercial, industrial: medium scale, unsubsidized LCOE = $49 - $185
  3. Rooftop solar / residential: smallest scale, unsubsidized LCOE = $177 - $282

*LCOE (levelized cost of electricity) - price for which a unit of electricity must be sold for system to break even

Compare costs with subsidies and for other resources on the Introduction to Renewable Energy Fast Facts

Costs of solar PV have fallen over time:

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  • Abundant, nondepletable source of energy
  • Low climate and environmental impact
  • Utility-scale solar PV: very low LCOE relative to fossil fuels, competitive with onshore wind
  • Continued PV cost declines and productivity gains
  • Declining energy storage costs enable grid integration
  • No fuel price volatility/risk
  • Short implementation timeframe from project start to electricity generation
  • Financial incentives (investment tax credit)
  • Renewable energy/climate targets
  • Rooftop solar PV: no transmission needed; no additional land use
  • Solar thermal heat: low-cost option for heating buildings, certain industrial processes


  • Grid integration challenges due to intermittency and duck curve*
  • Inconsistent/decreasing incentives
  • NIMBY/BANANA** concerns
  • US economic sanctions against panels manufactured in China, which is the largest solar PV manufacturer in the world
  • Lack of solar PV recycling capacity at end of life
  • Rooftop solar PV: very high LCOE; net metering reforms and utility rate redesign threaten economic viability
  • Solar thermal heat: hard to reach high enough temperatures for certain industrial processes

*Non-solar power plants are forced to ramp up quickly when the sun goes down because solar electricity drops and net demand peaks
**NIMBY - not in my backyard; BANANA - build absolutely nothing anywhere near anything

Climate Impact: Low

Low gradient
  • Near-zero emissions

Environmental Impact: Low

Low gradient
  • No air pollution
  • Little / no water use
  • Land use and habitat impact can be significant

Updated January 2024

Before You Watch Our Lecture on
Solar Energy

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential videos and readings below before watching our lecture on Solar Energy. Include selections from the Optional and Useful list based on your interests and available time.


Optional and Useful

Our Lecture on
Solar Energy

This is our Stanford University Understand Energy course lecture on solar energy. We strongly encourage you to watch the full lecture to understand solar as an energy system and to be able to put this complex topic into context. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Kirsten Stasio

Presented by: Kirsten Stasio, Adjunct Lecturer, Civil and Environmental Engineering, Stanford University; CEO, Nevada Clean Energy Fund (NCEF)
Recorded on: November 22, 2022   Duration: 73 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Significance of Solar Energy
13:06 Solar PV Technology
30:26 Solar PV Market Trends
49:59 Solar PV Environmental Impact
54:08 Solar PV Economics
58:12 Solar Thermal Heat
1:04:20 Concentrating Solar Power (CSP)
1:12:40 Conclusion

Lecture slides available upon request.

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Additional Resources About
Solar Energy

Fast Facts Sources

More details available on request.
Back to Fast Facts