Can my solar system still generate power on cloudy, rainy, or even snowy days? How much will the efficiency decrease? What is the power generation gap between winter and summer?

Solar Power GenerationSolar EnergyPower GenerationEfficiencyWeather
Created At: 7/24/2025Updated At: 8/18/2025
Answer (1)

This is an excellent question and one of the most practical concerns for all potential solar users. Many mistakenly believe solar only works under blazing sun, but the reality is far more optimistic.

Let me address these three closely related questions in detail.

1. Can it still generate power on cloudy, rainy, or even snowy days?

Core Answer: Yes! But efficiency decreases.

Solar photovoltaic (PV) panels generate electricity by relying on "photons," not "temperature" or "direct sunlight." The scientific term is the "photovoltaic effect." As long as there is visible light—even weak, scattered light filtering through clouds—it can excite the semiconductor material to produce an electric current.

  • Cloudy Days: This is the most common scenario. Clouds block most direct sunlight, but a significant amount of scattered light still reaches the ground. Therefore, the solar system still generates power, though its output is noticeably lower. Think of it like this: sunny days are "fast charging," cloudy days are "slow charging."

    • Generation Efficiency: Typically, on cloudy days, generation efficiency is about 10% ~ 30% of the peak power on a sunny day. For example, a 5kW system might output 4.5kW at noon on a sunny day, but only 0.5kW ~ 1.5kW at noon on a cloudy day. This can still meet the power needs of standby or low-power appliances.

  • Rainy Days: Rain clouds are thicker, resulting in weaker light and slightly lower generation efficiency than on cloudy days. However, the rain itself offers a free benefit—it cleans the solar panels! Rainwater washes away accumulated dust, bird droppings, and other debris. After the rain clears, the system's efficiency may actually improve due to the cleaner panel surfaces.

  • Snowy Days: This is the most unique situation, with two scenarios:

    • Light Snow or Dusting: Similar to rainy days, light is weak, efficiency is low, but the system still operates.
    • Snow Cover: If thick snow completely covers the panel surface, blocking light, the system will temporarily stop generating power. This is the only scenario where generation stops completely.
    • Snow's "Double-Edged Sword" Effect:
      • Benefit: As snow begins to melt and slide off the panels, it acts like a "squeegee," cleaning the surface very effectively. More importantly, snow on the ground acts like a giant reflector, bouncing sunlight onto the panels. This "snow albedo effect" can sometimes result in generation exceeding that of a typical sunny day without snow in the days immediately after a snowfall!
      • Drawback: Prolonged heavy snow cover reduces total generation, and excessive snow weight can stress the roof and mounting structure (though proper installation accounts for load-bearing capacity).

2. Is there a big difference in power generation between winter and summer?

Core Answer: The difference is very significant.

This is primarily determined by two key factors: daylight hours and solar altitude angle.

  • Summer (e.g., Northern Hemisphere):

    • Longer Daylight Hours: Days are long, often light by 5-6 AM and dark after 7-8 PM, providing over 12 hours of effective generation time.
    • High Solar Altitude Angle: The sun is nearly overhead, striking the panels at a near-vertical angle, delivering the highest energy density and generation efficiency.
    • Disadvantage: Very high temperatures (e.g., over 35°C/95°F) can slightly reduce panel efficiency. The optimal operating temperature for solar panels is around 25°C (77°F); efficiency decreases slightly as temperature rises. However, this effect is far outweighed by the advantage of longer daylight hours.
    • Conclusion: Summer is the absolute peak of annual generation. Monthly output can be 2 to 3 times higher than in winter.

  • Winter:

    • Shorter Daylight Hours: Days are short, light may not arrive until 7-8 AM and darkness falls by 4-5 PM, significantly reducing effective generation time.
    • Low Solar Altitude Angle: The sun is low in the sky, its rays pass through a thicker layer of atmosphere (reducing energy), and strike the panels at a low angle (lowering energy density).
    • Advantage: Lower winter temperatures help solar panels maintain higher conversion efficiency. On clear, cloudless winter days, hourly generation efficiency can be quite high despite the shorter day.
    • Conclusion: Winter is the lowest period for annual generation.

A helpful analogy: Think of a solar system like a bucket collecting rainwater.

  • Summer is like a long-lasting, heavy downpour – the bucket fills quickly.
  • Winter is like a brief, light drizzle – the bucket collects only a small amount.

In summary, as a solar user, it's important to accept and understand this natural "seasonal fluctuation." When planning household electricity use, consider:

  • Summer surplus: Feel free to use high-power appliances like air conditioning, or sell/store excess power.
  • Winter deficit: You may need to rely more on grid power.

Understanding these patterns means you won't feel anxious about reduced output on cloudy days or in winter. Instead, you can coexist with your solar system more scientifically and calmly.

Created At: 07-24 11:23:23Updated At: 08-05 12:30:47