Solar panels are devices that convert sunlight into electricity. Most solar panels use photovoltaic, or PV, cells made from semiconductor materials such as silicon. The cells produce direct-current electricity, and an inverter changes it into alternating current for homes, businesses and the electric grid.
A single solar cell produces only a small amount of power. Manufacturers connect many cells to make one panel, then connect multiple panels to create an array large enough for a home, commercial building or utility-scale power plant.
Solar Panels at a Glance
| Term | Meaning |
|---|---|
| Solar cell | The basic unit that converts sunlight into electricity |
| Solar panel or module | A weather-protected group of connected solar cells |
| Solar array | Multiple solar panels connected together |
| PV system | Panels, inverter, mounting equipment, wiring and, sometimes, a battery |
| Inverter | Converts the panels' DC electricity into AC electricity |
| Solar battery | Stores electricity for use when the panels produce little or no power |
How Do Solar Panels Work?
Solar panels work through the photovoltaic effect:
- Sunlight reaches the solar cells. Sunlight contains energy in particles called photons.
- The semiconductor absorbs the light. In most panels, silicon absorbs some of the photons' energy.
- Electrons begin moving. The absorbed energy causes electrons to flow through the cell, producing direct-current electricity.
- The inverter changes the electricity. Homes and the electric grid generally use alternating current, so the inverter changes the panel's DC output into AC power.
- The electricity is used or stored. It can power a building, flow to the grid or charge a battery.
What Are Solar Panels Made Of?
A typical photovoltaic panel contains:
- Silicon photovoltaic cells
- Protective glass or another durable outer layer
- Encapsulating materials that protect the cells from moisture
- Electrical contacts and wiring
- A frame and mounting system
- A junction box that connects the panel to the rest of the system
These parts protect the cells from outdoor conditions while allowing sunlight to reach the semiconductor material.
What Is the Difference Between a Solar Panel and a Solar System?
A solar panel is one module made from connected solar cells. A complete solar power system includes additional equipment, such as:
- Multiple solar panels
- An inverter or microinverters
- Mounting equipment
- Electrical wiring and safety equipment
- A utility meter for a grid-connected system
- A battery, if the system includes energy storage
A panel produces electricity, but it usually cannot power standard household circuits on its own. The inverter and other system components make the electricity usable in a building.
Do Solar Panels Work on Cloudy Days?
Yes. Solar panels can produce electricity whenever usable sunlight reaches their cells, including on cloudy days. Their output usually falls when the available sunlight is weaker.
Production also changes with the time of day, season, location, panel angle, shading, dirt and temperature. Solar panels generally do not produce electricity at night because there is no sunlight. A battery or connection to the electric grid can supply power when the panels are producing little or none.
What Are the Main Types of Solar Panels?
The main types are monocrystalline, polycrystalline and thin-film panels.
Monocrystalline Panels
Monocrystalline panels use silicon wafers made from a single crystal structure. They are often used where roof space is limited because they generally provide strong power output for their size.
Polycrystalline Panels
Polycrystalline panels use silicon made from multiple crystal structures. They are an established type of crystalline-silicon panel. Choosing between panel types also involves efficiency, available space, temperature performance, warranty and total system cost.
Thin-Film Panels
Thin-film panels use thin layers of photovoltaic material rather than conventional crystalline-silicon wafers. They can suit some large-area, lightweight or specialized applications, while rooftop systems commonly use crystalline-silicon technology.
What Are the Benefits of Solar Panels?
Solar panels can:
- Generate electricity without fuel combustion during operation
- Reduce the amount of electricity a building buys from the grid
- Supply power in remote locations without conventional power lines
- Work in rooftop systems and large solar farms
- Charge batteries for later use
- Be installed on roofs, ground-mounted structures and other suitable locations
Solar photovoltaic systems do not produce air pollution or carbon dioxide emissions during operation. Manufacturing, transport, installation and disposal still have environmental impacts.
What Are the Limitations of Solar Panels?
The main limitations are variable output, space requirements and the need for suitable system conditions.
- Variable output: Production changes with sunlight and weather.
- Shading: Trees, buildings and roof obstructions can reduce production.
- Space requirements: Higher electricity demand generally requires more panel area.
- No built-in storage: Panels produce electricity, while batteries store it.
- Roof suitability: An old, damaged or heavily shaded roof may not be suitable for installation.
- Heat effects: Solar cells generally work more efficiently at lower temperatures. Excessive heat can reduce voltage and output.
Are Solar Panels the Same as Solar Water Heaters?
No. Photovoltaic solar panels produce electricity. Solar thermal collectors capture sunlight as heat, usually to heat water or air. Concentrating solar-thermal power plants use mirrors and heat to generate electricity at a larger scale. These technologies use sunlight differently from photovoltaic panels.
Bottom Line
Solar panels use photovoltaic cells to convert sunlight into electricity. An inverter converts the panels' DC output into AC power for a building or the electric grid. A system's output depends on sunlight, shading, panel orientation, temperature and the equipment used.