Several external factors can contribute to a decrease in the power output of solar panels. These factors can affect the efficiency and performance of solar panels, resulting in insufficient power generation.

1. Shading: Shading from objects such as nearby buildings, trees, or debris can significantly reduce the amount of sunlight reaching the solar panels, thereby lowering their power output.
2. Incidence angle: The angle at which sunlight strikes the solar panel can impact its efficiency. Solar panels are designed to operate optimally when the sunlight falls perpendicularly on their surface. If the angle of incidence is not optimal, the power output may decrease.
3. Temperature: High temperatures can affect the performance of solar panels, leading to a decrease in efficiency. Most solar panels experience a drop in efficiency as temperatures rise above a certain threshold.
4. Dust and dirt: Accumulation of dust, dirt, or other debris on the surface of the solar panels can reduce the amount of sunlight absorbed, thereby lowering their power output.
5. Weather conditions: Variations in weather conditions such as cloud cover, fog, or smog can reduce the amount of sunlight reaching the solar panels, affecting their overall power generation.
6. Degradation: Over time, solar panels may experience degradation due to exposure to environmental factors, leading to a decrease in their efficiency and power output.
7. Inverter inefficiencies: Inverters are essential components of solar panel systems that convert the DC power generated by the solar panels into usable AC power. Inefficiencies in the inverters can result in a reduction in the overall power output of the solar panel system.
8. System design and installation: Poor system design or improper installation can lead to inefficiencies in the overall solar panel system, resulting in insufficient power generation.

Understanding these external factors is crucial for ensuring the optimal performance and efficiency of solar panel systems. Proper maintenance, regular cleaning, and system monitoring can help mitigate the impact of these external factors and ensure that solar panels operate at their highest potential.