Efficiency is one of the most important parameters of solar panels , showing how much of the solar energy falling on it can be converted into usable electricity by a given solar panel. This ratio is expressed as a percentage and fundamentally determines the performance of the system, the number of panels required, and the economics of the installation.
How is the efficiency of solar panels calculated?
The efficiency is the ratio of the electrical energy delivered by the solar panel (output energy) to the solar energy arriving at the solar panel (input energy):
Efficiency (%) = Output energy (W) / (Incoming solar energy (W/m²) × Solar panel surface (m²) ) x 100
Example:
- A 1 m² solar panel receives 1000 W/m² of solar energy (standard test conditions).
- If the output power of the solar panel is 200 W, then its efficiency is:
200 / ( 1000 x 1 ) x 100 = 20%
This means that the solar panel converts 20% of the solar energy falling on it into electricity.
What affects the efficiency of solar panels?
Solar cell technology:
- Monocrystalline solar cells: With the highest efficiency (18–22%), thanks to their single-crystal structure.
- Polycrystalline solar panels: Lower efficiency (15–18%), but cheaper production costs.
- Thin-film solar cells: The lowest efficiency (10–12%), but they are flexible and lightweight.
Incoming solar energy intensity: The strength and angle of solar radiation directly affect the performance of a solar panel.
Temperature: At high temperatures, the efficiency of solar panels decreases because the performance of semiconductors is temperature sensitive.
Shading and dirt: Shading, dust, or other dirt can reduce the amount of incoming solar energy, which reduces efficiency.
Weather conditions: Cloudy weather and diffuse radiation can also reduce system performance.
How can the efficiency of solar panels be improved?
Optimal installation angle and orientation: Solar panels should be positioned to receive as much sun as possible, usually at a 30–35° angle .
Use of solar tracking systems: Such systems follow the movement of the Sun, maximizing the capture of solar radiation.
Regular maintenance: Cleaning the panels and removing dirt is essential to maintain maximum efficiency.
Temperature control: Ventilating the panels can reduce overheating, maintaining efficiency.
Use of advanced inverters: Modern inverters better optimize system performance.
Comparison of solar panel efficiency
| Technology | Efficiency (%) | Features |
|---|---|---|
| Monocrystalline | 18–22% | High efficiency, smaller space requirement |
| Polycrystalline | 15–18% | Cheaper, average performance |
| Thin-film | 10–12% | Flexible, lightweight, takes up more space |
Example of efficiency calculation
A household's annual energy requirement is 5,000 kWh , and a 20 m² solar panel system can be installed on the roof.
If the efficiency of the solar panels is 15%:
Annual production: 20 m² x 1000 W/m² × 0.15 × 365 days × 5 hours/day = 5475 kWh
If the efficiency is 20%:
Annual production: 20m² × 1000W/m² × 0.20 × 365 days × 5 hours/day = 7300kWh
A higher efficiency solar panel can meet a greater energy demand in fewer places.
Summary
The efficiency of solar panels fundamentally determines the performance, economy and space requirements of the system. Higher efficiency not only results in higher energy yield, but also helps reduce long-term operating costs. Optimal installation conditions and regular maintenance are essential to achieve maximum performance.