Solar panels have gone from a niche technology to one of the cheapest sources of new electricity in many parts of the world. But how does a flat panel on a roof actually create power from sunlight?

The photovoltaic effect

Most solar panels are made of many small cells, usually built from silicon. When sunlight hits a cell, its energy knocks electrons loose from their atoms. The cell is designed with layers that push these freed electrons in one direction, creating an electric current. This process is called the photovoltaic effect.

From panel to plug

Solar cells produce direct current (DC), but homes and the power grid use alternating current (AC). A device called an inverter converts DC into AC so the electricity can power lights, appliances and devices, or be sent back to the grid.

What about cloudy days and nights?

Panels still produce some power on cloudy days, just less. At night they produce none. That is why many systems are connected to the grid, or paired with batteries that store extra energy produced during the day.

Every hour, the sun delivers more energy to Earth than humanity uses in a year.

Why solar keeps getting cheaper

• Mass production has driven down manufacturing costs.
• Cells have become more efficient at converting sunlight.
• Installation methods have improved and become faster.

Is solar right for you?

It depends on how much sun your location gets, your roof's direction and shade, local electricity prices and any available incentives. Sunny regions such as North Africa and southern Europe are especially well suited.

Looking ahead

Researchers are working on new materials and designs that could make panels even more efficient and flexible. Combined with better batteries, solar is set to play a growing role in the world's energy mix.