How Solar Panels Work: Photovoltaic Technology and What Affects Efficiency

Solar power is one of the fastest-growing sources of electricity worldwide, yet many people are unsure how a flat panel on a roof actually produces power. The answer lies in a phenomenon known as the photovoltaic effect, and understanding it makes it easier to judge what affects a system's performance.

The photovoltaic effect in simple terms

Most solar panels are built from solar cells made of silicon, a semiconductor. When sunlight, which is made of packets of energy called photons, strikes a cell, it can knock electrons loose from silicon atoms. The cell is constructed with two layers that have different electrical properties, creating an internal electric field. This field pushes the freed electrons in a single direction, producing a flow of electric current.

From sunlight to household electricity

1. Light absorption: photons strike the solar cells and free electrons.
2. Current generation: the internal electric field directs the electrons, creating direct current (DC).
3. Inversion: an inverter converts DC into alternating current (AC), the type used by home appliances and the electrical grid.
4. Use, storage or export: power is consumed on site, stored in a battery, or sent to the grid depending on the system design.

Main types of solar cells

• Monocrystalline silicon: made from a single crystal structure; generally higher efficiency and a sleek dark appearance, often at a higher price.
• Polycrystalline silicon: made from multiple silicon fragments; historically lower cost with slightly lower efficiency.
• Thin-film: lightweight and flexible layers of photovoltaic material; useful in specialized applications though typically less efficient on rooftops.
• Emerging technologies: perovskite and tandem cells are being researched and commercialized to push efficiency beyond what single silicon cells can reach.

What determines real-world efficiency?

Panel efficiency describes how much incoming sunlight is turned into electricity. Laboratory records are higher than commercial products, and actual output depends on many conditions.

Sunlight and location

Latitude, climate and local weather determine how much solar energy reaches a panel. Clear, sunny regions produce more than cloudy ones, though panels still generate some power in diffuse light.

Orientation and tilt

Panels perform best when angled to face the sun for most of the day. In the northern hemisphere, that generally means facing south at a tilt that suits the latitude.

Shading

Even partial shade from trees, chimneys or nearby buildings can reduce output significantly. Modern systems use optimizers or microinverters to limit the impact.

Temperature

Counterintuitively, solar cells lose some efficiency as they heat up. A cool, bright day can be better for output than a scorching one.

Dirt and degradation

Dust, snow and debris reduce light reaching the cells, and all panels slowly lose capacity over time. Manufacturers commonly provide performance warranties spanning decades.

Is solar right for you?

Factors to consider include your roof's orientation and condition, local electricity prices, available incentives, and how much power you use during daylight hours. Getting multiple quotes and asking installers for production estimates based on your specific site is a sensible first step.

Key takeaways

Solar panels turn sunlight directly into electricity using semiconductor physics, with no moving parts. Technology continues to improve, but site conditions such as sunlight, shading and orientation remain the biggest influences on how much energy a system actually delivers.