Solar panels generate electricity directly from sunlight with no moving parts and no emissions during operation. The core principle — the photovoltaic effect — was first observed in the 19th century, but practical solar cells only became widespread in recent decades as costs fell.
The photovoltaic effect
Most solar cells are made from silicon, a semiconductor. When particles of light (photons) strike the cell, they knock electrons loose from silicon atoms. An internal electric field, created by layering two types of silicon, sweeps these freed electrons in one direction — and a flow of electrons is an electric current.
From cells to systems
A single cell produces only a small voltage, so cells are wired together into modules (panels), and panels into arrays. Panels produce direct current (DC), but homes and grids use alternating current (AC), so an inverter converts the electricity. Mounting, wiring and safety equipment complete the system.
What affects output
Output depends on sunlight intensity, panel orientation and tilt, temperature (cells actually lose a little efficiency when very hot), shading, and dirt or snow cover. Well-sited systems in sunny regions produce far more over a year than identical systems in cloudy northern locations — though panels still generate useful power on overcast days.
Solar in the energy mix
Solar is now one of the fastest-growing energy sources worldwide, deployed both as rooftop systems and as utility-scale solar farms. Because sunlight is intermittent, grids pair solar with other sources, storage (such as batteries) and demand management to keep supply reliable around the clock.