Solar power

Solar power turns sunlight into electricity. There are two main ways to do this: directly, using photovoltaics (PV), or indirectly, using concentrated solar power. PV panels rely on the photovoltaic effect to generate an electric current when light hits them. Concentrated solar power systems use lenses or mirrors that track the sun to focus a large patch of sunlight onto a small area, creating intense heat that typically runs a steam turbine.

Photovoltaics started out powering small things—like a single solar cell in a calculator or an off-grid rooftop system for a remote home. Commercial concentrated solar power plants came along in the 1980s. After that, as solar panel prices dropped, the amount of grid-connected solar PV capacity and electricity produced has roughly doubled every three years. Today, solar makes up three-quarters of all new power generation capacity, with millions of rooftop installations and giant, gigawatt-scale solar farms being built all the time.

In 2025, solar supplied 9% of the world’s electricity. The year before, in 2024, it provided 7% of global electricity and over 1% of primary energy (or 2.7% using the substitution method), and it added twice as much new electricity as coal did. For new power plants in most countries, utility-scale solar is now the cheapest source of electricity, tied with onshore wind. Nearly half of all solar installed in 2022 was on rooftops. China leads the world in both making and installing solar: it produces 98% of solar wafers, 92% of solar cells, and 85% of solar panels, and in the first half of 2025 it accounted for more than 55% of global installed capacity.

To electrify the economy and fight climate change, much more low-carbon power is needed. In 2022, the International Energy Agency noted that better grid integration and solutions to policy, regulation, and financing problems are still required. Still, solar could greatly lower energy costs, and it’s important for energy security.

**Potential**

Geography matters for solar potential because some places get more sun than others. Areas closer to the equator generally receive more sunshine. But solar panels that can track the sun’s position can boost potential significantly in places farther from the equator. Cloud cover during the day reduces the light available to solar cells.

Land availability also strongly affects how much solar can be deployed. Even though solar panel prices have dropped a lot in recent years, a big hurdle for many countries wanting large-scale solar is the land it requires and the related limits. Utility-scale solar farms need a lot of surface area, which is hard to find in dense cities or heavily built-up areas. So, large solar installations often end up in rural spots or far from major population centers. That can mean extra infrastructure, like upgrading rural grids and building high-voltage transmission lines, to get the electricity to where people live.

**Technologies**

Solar power plants use one of two technologies:

- **Photovoltaic (PV) systems** use solar panels on rooftops or in ground-mounted solar farms to turn sunlight directly into electricity. - **Concentrated solar power (CSP) systems** use mirrors or lenses to focus sunlight into extreme heat, making steam that drives a turbine to generate electricity.

**Solar Cells**

The photovoltaic effect in solar cells converts light into electric current. The first solar cell was built by Charles Fritts in the 1880s. German industrialist Ernst Werner von Siemens was one of the people who saw how important this discovery was. In 1931, German engineer Bruno Lange made a photo cell using silver selenide instead of copper oxide, though those early selenium cells turned less than 1% of incoming light into electricity. After Russell Ohl’s work in the 1940s, researchers Gerald Pearson, Calvin Fuller, and Daryl Chapin created the silicon solar cell in 1954. Those early cells cost US$286 per watt and had efficiencies of 4.5–6%. In 1957, Mohamed M. Atalla developed the process of silicon surface passivation using thermal oxidation at Bell Labs. That surface passivation process has been crucial for solar cell efficiency ever since.

As of 2022, over 90% of the market uses crystalline silicon. Other types include thin-film solar cells, made by depositing one or more thin layers of photovoltaic material on a substrate like glass, plastic, or metal.

A photovoltaic system’s array produces direct current (DC) power, which changes with sunlight intensity. For practical use, this usually needs to be converted to alternating current (AC) using inverters. Multiple solar cells are connected inside panels. Panels are wired together into arrays, then linked to an inverter, which delivers power at the right voltage and, for AC, the correct frequency and phase.

Many residential PV systems are connected to the grid where possible, especially in developed countries with big markets. In these grid-connected systems, energy storage is optional. For certain uses—like satellites, lighthouses, or in developing countries—batteries or extra generators are often added as backups. These stand-alone systems can run at night and during times of limited sunlight.

**Concentrated Solar Power**

Concentrated solar power (CSP), also called “concentrated solar thermal,” uses lenses or mirrors with tracking systems to concentrate sunlight. The resulting heat then generates electricity from a conventional steam-driven turbine.