Do Solar Panels Work in Monsoon & Cloudy Weather? The Short Answer
Yes — solar panels still generate electricity on cloudy days and during monsoon season. They don't need direct sunlight, only daylight (solar irradiance). But output does drop — typically to 10–25% of peak capacity on heavily overcast days.
For Indian homeowners considering solar, this is one of the most common concerns. Let's break it down with real numbers.
How Solar Panels Work on Cloudy Days
Solar panels work by converting photons (light particles) into electricity via the photovoltaic effect. On cloudy days:
- Diffuse light (scattered sunlight through clouds) still reaches your panels
- A 3kW system that produces 12–15 units/day in summer might produce 3–6 units on a heavily overcast monsoon day
- Partly cloudy days: output is roughly 50–70% of peak
- Fully overcast/heavy rain: output drops to 10–25% of peak
Important: During monsoon, you also consume less electricity (less AC, fewer fans at full speed), so the deficit is smaller than you might expect.
India's Monsoon Season — State-by-State Impact
| Region | Monsoon Duration | Solar Impact | Annual GHI Impact |
|---|---|---|---|
| Kerala, Coastal Karnataka | June–October (5 months) | High — heavy rains | ~15–20% annual loss |
| Maharashtra, Goa | June–September (4 months) | Moderate-high | ~12–15% annual loss |
| West Bengal, Northeast | June–September | High | ~18% annual loss |
| Delhi, UP, Bihar | July–September (3 months) | Moderate | ~8–12% annual loss |
| Rajasthan, Gujarat | Short/Light monsoon | Low | ~5–8% annual loss |
| Tamil Nadu | Northeast monsoon (Oct–Dec) | Low-moderate | ~10% annual loss |
Even in Kerala — India's rainiest state — solar panels generate enough annual electricity to give a positive ROI. The system is sized to account for monsoon months.
Real Numbers: Annual Solar Generation Including Monsoon
Solar installers use "Global Horizontal Irradiance" (GHI) data that already factors in historical cloud cover and monsoon patterns. A properly sized system in India delivers:
- Mumbai (3kW system): ~3,800–4,200 units/year (including 4 months monsoon)
- Delhi (3kW system): ~4,200–4,600 units/year (shorter monsoon)
- Bangalore (3kW system): ~4,000–4,400 units/year
- Chennai (3kW system): ~4,400–4,800 units/year
- Kolkata (3kW system): ~3,600–4,000 units/year
Your inverter will show you daily generation — expect significantly lower numbers during peak monsoon months.
Do Solar Panels Work in Heavy Rain?
Yes, with a bonus: rain actually cleans your panels, removing dust and bird droppings that reduce efficiency. A post-rain panel often works better than a dusty dry-season panel.
Rain doesn't damage solar panels — they're rated IP67 (completely waterproof) and tested for hail up to 25mm diameter. Indian panels must also meet IEC 61215 and IEC 61730 standards that include rain and humidity testing.
What About Solar Panels During Cyclones?
India's coasts (Odisha, Andhra Pradesh, Tamil Nadu, Gujarat) face cyclones. Premium solar panels are rated for wind speeds up to 2,400 Pa (about 200 km/h). Proper mounting on RCC/metal roofs with correct tilt angles handles cyclone-prone areas well. Consult your installer about cyclone-rated racking systems if you're in a cyclone zone.
Tips to Maximise Solar Output Year-Round in India
- Choose high-efficiency panels: Monocrystalline panels (20–22% efficiency) perform better than polycrystalline in low-light/diffuse conditions. Worth the ₹5,000–10,000 extra per kW.
- Correct tilt angle: Panels tilted at your latitude angle capture more diffuse radiation during monsoon months.
- Oversizing slightly: If your roof allows, installing 10–20% more capacity than your calculated requirement compensates for monsoon months.
- Net metering is your friend: Export surplus from sunny months, draw from grid during monsoon months — your annual bill nets out to near zero.
- Battery backup (for off-grid): If you're in an area with grid outages, size your battery bank to cover 2–3 days of monsoon generation (not just 1 day).
- Panel cleaning after monsoon: Once the monsoon ends, a professional cleaning restores full efficiency.
Monsoon Performance: Monocrystalline vs Polycrystalline
Monocrystalline panels have a clear advantage in diffuse/low-light conditions due to their higher cell efficiency. In monsoon-heavy states like Kerala, Maharashtra, and West Bengal, mono panels generate 5–10% more electricity annually compared to poly panels of the same rated wattage. The price difference has narrowed considerably in 2025-26, making mono the recommended choice for most Indian homes.
The Bottom Line
Solar panels work in monsoon India — every solar installer knows this and factors it into their ROI calculations. Typical Indian solar systems have payback periods of 4–6 years and 25-year warranties, meaning you earn for 19–21 years after payback. Monsoon months reduce output but don't change the fundamental economics.
If you're concerned about monsoon impact in your specific city, ask your installer for the GHI data and month-wise generation estimate before signing. Any credible installer will have this data.