Solar power, also called solar electricity, is the process of changing sunlight into electricity. This can happen directly through photovoltaics (PV), which use solar panels, or indirectly through concentrated solar power (CSP), which uses mirrors or lenses to focus sunlight. Solar panels use the photovoltaic effect to turn light into electricity. CSP systems use mirrors or lenses and tracking devices to concentrate sunlight into a hot spot, which is often used to power a steam turbine.

Photovoltaics (PV) were first used for small and medium-sized purposes, such as powering calculators with one solar cell or providing electricity to homes not connected to the main power grid. Commercial concentrated solar power plants were first built in the 1980s. Since then, as the cost of solar panels has decreased, the amount of electricity produced by grid-connected solar PV systems has doubled every three years. Three-quarters of new electricity generation capacity added globally is from solar power, with both millions of rooftop solar systems and large-scale solar power plants being built.

In 2024, solar power provided 7% of the world’s electricity and over 1% of total energy (2.7% by a different calculation method). It added twice as much new electricity as coal did. Along with onshore wind power, large-scale solar energy is the cheapest source of electricity for new projects in most countries. China produces about half of the world’s solar power. Nearly half of the solar power installed in 2022 was placed on rooftops.

More low-carbon energy is needed to power homes and reduce climate change. In 2022, the International Energy Agency stated that more work is required to connect solar power to the electrical grid and address challenges related to rules, policies, and funding. Despite these challenges, solar power can help lower energy costs. Solar energy is important for ensuring a stable and secure energy supply.

Potential

Geography influences how much solar energy can be collected because some areas get more sunlight than others. Areas near the equator usually receive more sunshine than places farther away. Solar panels that move to follow the Sun's position can help increase solar energy collection in areas farther from the equator. Clouds during the day can block sunlight, reducing the amount of light that reaches solar panels. The amount of available land also plays an important role in how much solar energy can be produced.

Technologies

Solar power plants use two main types of technology:

• Photovoltaic (PV) systems use solar panels, which can be placed on rooftops or in large ground-based solar farms. These panels convert sunlight directly into electricity.
• Concentrated solar power (CSP) systems use mirrors or lenses to focus sunlight into intense heat. This heat is used to create steam, which turns a turbine to generate electricity.

The photovoltaic effect in solar cells changes light into electric current. The first solar cell was built by Charles Fritts in the 1880s. Ernst Werner von Siemens, a German industrialist, recognized the importance of this discovery. In 1931, German engineer Bruno Lange created a photo cell using silver selenide instead of copper oxide. However, these early cells converted less than 1% of sunlight into electricity. In the 1940s, researcher Russell Ohl’s work led to the creation of the first silicon solar cell in 1954 by Gerald Pearson, Calvin Fuller, and Daryl Chapin. These early cells cost $286 per watt and had efficiencies of 4.5–6%. In 1957, Mohamed M. Atalla developed a process called silicon surface passivation at Bell Labs, which improved solar cell efficiency.

As of 2022, over 90% of the solar market uses crystalline silicon. A photovoltaic system produces direct current (DC) power, which changes based on sunlight intensity. For practical use, this DC power is usually converted to alternating current (AC) using inverters. Solar cells are grouped into panels, and panels are connected to form arrays. These arrays are linked to an inverter, which adjusts the power to the needed voltage and frequency for AC electricity.

Many homes in developed countries connect their solar systems to the electric grid when available. In these systems, energy storage is not always needed. In other cases, like on satellites, lighthouses, or in areas without reliable electricity, batteries or backup generators are added. These stand-alone systems allow power to be used at night or during low sunlight.

In a vertical agrivoltaics system, solar cells are placed vertically on farmland, allowing crops to grow and energy to be produced at the same time. Other setups include floating solar farms, solar canopies over parking lots, and rooftop solar installations.

A thin-film solar cell is a second-generation solar cell made by adding thin layers of photovoltaic material to a surface, such as glass, plastic, or metal. These cells are used in technologies like cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous thin-film silicon (a-Si).

A perovskite solar cell (PSC) uses a special material called a perovskite-structured compound, often made from lead or tin halides. These materials are inexpensive and easy to make. Laboratory tests show that perovskite solar cells have improved from 3.8% efficiency in 2009 to 27% in 2025 for single-junction cells and up to 34.85% in silicon-based tandem cells. However, challenges like long-term stability, sensitivity to moisture, and toxicity from lead remain. Managing lead toxicity is important because it can cause health issues, such as neurological disorders.

Concentrated solar power (CSP), also called concentrated solar thermal, uses mirrors or lenses and tracking systems to focus sunlight. The heat from this focused light is used to generate electricity through steam-driven turbines.

As of 2021, the levelized cost of electricity from CSP is more than twice that of PV. By 2022, less than 1% of solar power came from CSP.

A hybrid system combines solar power with energy storage or other energy sources, such as hydroelectric, wind, or batteries. These systems can adjust power output to match demand or reduce fluctuations in solar power. Hydroelectric power is widely available, and adding solar panels near existing hydro reservoirs is useful because hydro is flexible, cheaper at scale than batteries, and existing power lines can often be used.

Development and deployment

Solar technology began developing in the 1860s because people thought coal would run out soon. Augustin Mouchot conducted experiments during this time. In 1884, Charles Fritts installed the first rooftop solar array using selenium cells that were 1% efficient on a building in New York City. However, solar technology development slowed in the early 1900s because coal and petroleum became more available, cheaper, and more useful. In the 1950s, Bell Telephone Laboratories tested silicon wafers coated with boron. Their "Bell Solar Battery" had 6% efficiency, with each square yard of panels producing 50 watts of power. The first satellite with solar panels was launched in 1957.

By the 1970s, solar panels were still too expensive for use outside of satellites. In 1974, only six homes in North America used solar power for heating or cooling. However, the 1973 oil shortage and the 1979 energy crisis led countries to change their energy policies and focus more on solar technology. Programs like the Federal Photovoltaic Utilization Program in the U.S. and the Sunshine Program in Japan helped promote solar use. Research centers were created in the U.S., Japan, and Germany. Between 1970 and 1983, solar installations grew quickly. President Jimmy Carter aimed for 20% of U.S. energy to come from solar by 2000, but his successor, Ronald Reagan, stopped funding for renewable energy research. Falling oil prices in the 1980s slowed solar growth until 1996.

Solar power grew steadily after 1996 because of better policies and lower costs. In 2023, China added 60% of the world’s new solar capacity. In the mid-1990s, residential, commercial, and large-scale solar projects began growing again due to oil supply problems, global warming concerns, and better economics of solar power. In the early 2000s, feed-in tariffs—policies that guarantee a fixed price for solar electricity—led to more investments in Europe.

Solar growth was first driven by Europe but later shifted to Asia, especially China and Japan, and many other countries. Chinese companies became the largest solar equipment manufacturers. Although concentrated solar power (CSP) capacity increased tenfold, it remained a small part of total solar energy because utility-scale solar costs dropped 85% between 2010 and 2020, while CSP costs dropped only 68% in the same period.

During the 2021–2022 energy crisis, rising material costs like polysilicon did not stop utility-scale solar from being the cheapest energy source in many countries because other energy costs, like natural gas, rose sharply. In 2022, global solar generation capacity reached over 1 terawatt for the first time. However, fossil fuel subsidies have slowed solar growth. Africa is now the fastest-growing solar market, supported mostly by China.

About half of all solar power is from large-scale projects. Solar is expected to become the largest renewable energy source by the end of the 2020s, surpassing hydropower. By 2050, large-scale solar is predicted to be the main electricity source in most regions except sub-Saharan Africa.

A photovoltaic power station, also called a solar park or solar farm, is a large system that connects to the power grid and sells electricity to businesses. Unlike smaller solar systems, these stations supply power to the entire grid, not just local users. Utility-scale solar is different from concentrated solar power (CSP), which uses heat to generate electricity. So far, photovoltaic technology has been used more widely than CSP. In 2019, 97% of large-scale solar power was from photovoltaic systems.

In some countries, solar power stations are rated in megawatt-peak (MWp), which means the maximum power the panels can produce. In others, the size and efficiency of the panels are listed. Countries like Canada, Japan, Spain, and the U.S. often use megawatt-ac (MWac), a measure that compares directly to other power sources. Most solar farms are at least 1 MWp. By 2018, the largest solar farms exceeded 1 gigawatt. By the end of 2019, over 9,000 solar farms larger than 4 MWac had a combined capacity of more than 220 gigawatts.

Most large solar farms are owned by independent companies, but more community and utility-owned projects are being developed. In the past, these projects relied on government incentives like feed-in tariffs or tax credits. However, as costs dropped in the 2010s and solar became cost-competitive with other energy sources, these incentives are no longer needed in most places.

Concentrated solar power (CSP) plants, also called solar thermal power stations, were first built in the 1980s. The Ivanpah Solar Power Facility in California’s Mojave Desert is the largest CSP plant at 377 megawatts. Other large CSP plants are in Spain, including Solnova, Andasol, and Extresol. The main advantage of CSP is its ability to store heat, allowing electricity to be produced for up to 24 hours. Many CSP plants use 3 to 5 hours of thermal storage to meet peak electricity demand, which usually happens around 5 p.m.

Economics

Solar power is often the least expensive way to produce electricity in many countries. The cost of solar power includes the price of the solar panels, the frames that hold them, wiring, inverters, labor, any land needed, connecting to the power grid, maintenance, and the amount of sunlight the location receives.

Solar panels do not need fuel and can last 25 to 40 years. Because of this, the initial cost of buying and financing solar systems makes up most of the total cost, about 80% to 90%. This can be a problem in some countries where agreements to pay for solar power may not be kept, such as in parts of Africa. Some countries are thinking about setting maximum prices for solar power, while others prefer agreements that guarantee a certain price.

The cost of high-power solar panels has dropped a lot over time. In 1982, the cost was about $27,000 per kilowatt. By 2006, it had dropped to about $4,000 per kilowatt. In 1992, a solar system cost about $16,000 per kilowatt, and by 2008, it was about $6,000 per kilowatt. In 2025, residential solar in the United States costs about $2.50 per watt, though solar shingles cost more. Utility-scale solar in 2025 costs about 25 cents per watt.

The amount of electricity solar power can produce in a region depends on how much sunlight it receives, which changes throughout the day and year. This is affected by the region’s latitude and weather. Solar power output also depends on temperature, wind speed, the type of sunlight, and how clean the panels are.

Onshore wind power is usually the cheapest electricity source in parts of Northern Eurasia, Canada, some areas of the United States, and Patagonia in Argentina. In other areas, solar power (or sometimes a mix of wind, solar, and other clean energy) is considered the best option. Research from Exeter University suggests that by 2030, solar power will likely be the least expensive energy source everywhere except some Nordic countries.

Regions with the highest yearly sunlight are usually in dry tropical and subtropical areas. Deserts near the equator often have little cloud cover and can get more than ten hours of sunlight daily. These hot deserts form the Global Sun Belt, which includes parts of North and Southern Africa, Southwest Asia, the Middle East, Australia, and smaller deserts in North and South America.

Solar power is (or is expected to become) the cheapest energy source in Central America, Africa, the Middle East, India, Southeast Asia, Australia, and other regions.

Maps show measurements of sunlight in different areas, including:
– North America
– South America
– Europe
– Africa and the Middle East
– South and Southeast Asia
– Australia
– The world

When people use solar power for their own needs, the time it takes to recover the cost depends on how much electricity they save by not buying it from the grid. However, solar energy is often produced at times when it is not needed, and some or all of the energy is sent back to the grid. Electricity is sold when there is extra, and bought when needed. The prices for selling and buying electricity affect how profitable solar power is. In many areas, the price paid for solar electricity sold to the grid is much lower than the price for electricity bought from the grid, which encourages people to use solar power themselves. Some countries, like Germany and Italy, have special programs to support self-use of solar energy. In some regions of Germany with many solar panels, rules limit how much electricity can be sent to the grid. Increasing self-use can help reduce the need to send electricity to the grid without wasting it.

Matching the times when solar energy is produced with when it is needed is important for using it efficiently. This can be improved with batteries or by adjusting when electricity is used. However, batteries are expensive, and their use may only be profitable if they provide other benefits, such as preventing power outages. Hot water storage tanks with electric heating can store solar energy at a lower cost. Appliances like dishwashers and washing machines can be used at times that match solar energy production, though their impact on solar use may be limited.

The goal of early solar energy policies was to help the industry grow by supporting small projects, even when solar was more expensive than other energy sources. These policies helped the industry become large enough to compete with other energy sources. Now that solar is cheaper, some policies aim to help countries become more energy independent, create high-tech jobs, and reduce carbon emissions.

Net metering is a way to price electricity for homes with solar panels. The price for electricity produced by solar panels is the same as the price paid by the customer for electricity from the grid. Customers are charged based on the difference between how much electricity they produce and use.

A community solar project is a solar power system that allows many people, including individuals, businesses, and organizations, to invest in it. Participants usually buy a share of the system’s power or energy output.

In some countries, taxes are added to the cost of importing solar panels.

Grid integration

Most electricity produced worldwide is used right away because traditional power generators can adjust to changes in demand, and storing electricity is usually more expensive. Solar power and wind power are sources of energy that change based on weather and time of day. This means all electricity from these sources must be used where it is made, sent through power lines to other places, or stored, such as in batteries. Solar energy is not available at night, so storing it to provide electricity continuously is important, especially in areas without a power grid and for future plans to use only renewable energy.

Solar power is not always available because it depends on the time of day and weather. However, solar energy can be predicted based on the time of day, location, and season. Adding solar power to an electricity system can be easier or harder depending on the area. In places with hot summers and mild winters, solar power often matches the need for cooling during the day.

Some solar power plants use thermal storage, such as high-temperature molten salts, to store energy. These salts are useful for storage because they are low-cost, can hold a lot of heat, and work well with traditional power systems.

In solar power systems that operate alone, batteries are used to store extra electricity. In systems connected to the power grid, extra electricity can be sent to the grid. Programs like net metering and feed-in tariffs allow these systems to receive credit for the electricity they produce. This credit helps cover electricity used from the grid when the system cannot meet demand, effectively trading with the grid instead of storing electricity. When solar and wind power make up a small part of the grid, other power sources can adjust their output. However, as these variable energy sources grow, the grid needs more balance. As costs for solar panels drop, more systems use rechargeable batteries to store extra electricity for later use, such as at night. These batteries help keep the grid stable by reducing sudden spikes in electricity use.

Common battery types used in home solar systems include nickel-cadmium, lead-acid, nickel metal hydride, and lithium-ion. Lithium-ion batteries may replace lead-acid batteries soon because they are being developed more and may cost less due to large production facilities, like Tesla Gigafactory 1. In the future, batteries from electric cars might be used to store electricity in a vehicle-to-grid system. Since most cars are parked 95% of the time, their batteries could send electricity to the power grid or receive it when needed.

Old batteries from electric vehicles can be reused. Other batteries used for solar systems include sodium-sulfur batteries and vanadium redox batteries, which are types of molten salt and flow batteries, respectively.

Solar power plants usually produce as much electricity as possible, even if it is not needed immediately. In systems without enough energy storage, other power sources like coal, biomass, natural gas, nuclear, or hydroelectricity adjust their output based on changes in solar power and electricity demand.

Traditional hydroelectric dams work well with solar power because water can be stored or released as needed. In areas without suitable geography, pumped-storage hydroelectricity uses solar power to move water to a high reservoir during sunny days. At night or during bad weather, the stored water is released to generate electricity.

Hydroelectric and natural gas plants can quickly change their output to meet electricity needs. Coal, biomass, and nuclear plants take longer to adjust and can only follow predictable changes in demand. In areas where solar power makes up more than 20–40% of total electricity, the grid may need more connections, storage, or ways to manage electricity use. In countries with high solar power, like Australia, electricity prices can drop below zero during the day when solar production is high, encouraging investment in battery storage.

Using wind and solar power together helps because they often produce electricity at different times of the day and year. This makes their combined power supply more steady and less likely to fluctuate. Solar power is seasonal, especially in areas far from the equator, which means long-term storage solutions, such as hydrogen or pumped hydroelectricity, may be needed.

Environmental effects

Solar power is cleaner than electricity made from fossil fuels and is better for the environment than burning fuels. Solar power does not create harmful pollution when it is used, but making the solar panels does produce some pollution. The amount of carbon emissions from making solar panels is less than 1 kilogram of CO2 per watt of power, and this number is expected to decrease as companies use more clean energy and recycled materials. Solar power has a cost to the environment when panels are made, which takes several years to balance out with the clean energy it provides. However, solar panels can provide clean energy for about 30 years after they are made.

Over their entire life cycle, solar farms produce less than 50 grams of greenhouse gases for every kilowatt-hour of electricity made. If batteries are used to store energy, this number could be as high as 150 grams per kilowatt-hour. In comparison, a gas power plant without carbon capture emits about 500 grams per kilowatt-hour, and a coal power plant emits about 1,000 grams per kilowatt-hour. Like all energy sources, most emissions from solar power come from building and transporting the panels. Using low-carbon energy in these processes would further reduce emissions.

Solar power produces about 7 watts of power per square meter on average, compared to 240 watts per square meter for nuclear power and 480 watts per square meter for gas. However, when land used for gas extraction and processing is considered, gas power uses about the same amount of land as solar. A 2021 study found that to get 25% to 80% of electricity from solar farms by 2050, solar panels would need to cover 0.5% to 2.8% of the European Union, 0.3% to 1.4% of India, and 1.2% to 5.2% of Japan and South Korea. Using large areas for solar farms might cause people to oppose it, and could lead to cutting down trees or using farmland. However, some countries, like South Korea and Japan, use land for farming under solar panels or use floating solar panels alongside other clean energy sources. Worldwide, solar power uses land in a way that has little effect on the environment. Using solar panels on buildings and other developed areas can reduce land use to levels similar to gas power.

Some harmful materials are used in making solar panels, but only in small amounts. As of 2022, the environmental impact of perovskite is unclear, but there is some concern that lead might be a problem.

A 2021 study by the International Energy Agency predicts that the demand for copper will double by 2040. The study warns that the supply of copper must grow quickly to meet the needs of large solar projects and upgrades to power grids. More tellurium and indium may also be needed.

Recycling may help reduce waste. Sometimes, older solar panels are replaced with newer, more efficient ones, and the old panels are reused in other countries, such as in Africa. Some countries have rules for recycling solar panels. Although solar power systems are already less expensive to maintain than other energy sources, some experts suggest that solar systems should be designed to be easier to repair.

Solar panels can raise local temperatures. In large solar farms in deserts, this effect can be stronger than the heat caused by cities.

A very small part of solar power is concentrated solar power. This type of solar power may use more water than gas power. This can be a problem because concentrated solar power needs strong sunlight, so it is often built in deserts.

Politics

Some people say that the economic benefits of switching to solar energy (and other clean energy sources) are so large that the change cannot be stopped. However, slowing this change could lead to more harm to the environment. The group that supports fossil fuels has been criticized for trying to delay the move to clean energy. Money given to fossil fuel industries by governments makes it harder to switch to clean energy. Once solar energy systems are built, they are not affected by political conflicts between countries, unlike oil and gas, which helps improve energy security. Some people who believe in limited government support solar energy because it reduces reliance on government and weakens the need for old electricity systems. However, some right-wing political groups are against or unsure about using solar energy. Far-right political parties have different views in different countries, with some opposing solar energy as part of their belief that climate change is not real. While some environmental groups support solar energy to help reduce climate change, others are against building new power lines.

As of 2022, more than 40% of the world’s solar panel materials are made in Xinjiang, China. This has raised concerns about human rights issues in that region. The International Solar Energy Society says that China’s control over solar manufacturing is not a major problem because they believe solar production will not grow beyond 400 billion USD per year, and other countries would have time to build their own industries if China stopped supplying materials. Companies may try to influence governments to support or oppose taxes on imported solar panels.