Why Are My Solar Panels Not Generating Enough Power? Complete Troubleshooting Guide

By PSI Editorial • June 8, 2026

Atomic Summary: The top reasons for low solar generation in Pakistan are dust accumulation (15-30% loss), partial shading from water tanks and trees, extreme heat reducing panel efficiency via temperature coefficient, inverter faults or grid voltage issues, and degraded wiring or MC4 connectors. This guide covers each cause with precise diagnostics and fixes.

You spent PKR 800,000 on a 10kW system, but your inverter app shows barely 5-6kW at peak noon. Your neighbor with the same system size seems to generate far more. Before panicking or blaming your installer, let us systematically diagnose every possible cause.

In most cases, the fix is simpler (and cheaper) than you think.

Quick Diagnostic Table: Identify Your Problem

Use this table to quickly narrow down the most likely culprit based on your symptoms:

Cause 1: Dust Accumulation — The Silent Killer

In Pakistani cities, this is the number one reason for underperformance. Lahore's smog, Karachi's sea salt mist, Multan's desert dust, and Islamabad's construction particles all coat your panels in a film that blocks sunlight.

How Much Power Does Dust Cost You?

• 1 week without cleaning: 10-15% generation loss
• 2 weeks without cleaning: 20-25% generation loss
• 1 month without cleaning (Punjab smog season): 30-40% generation loss

The Fix

1. Clean your panels every 10-15 days using soft water and a microfiber mop
2. Clean in early morning (before 8 AM) or after sunset — never clean hot panels as thermal shock can crack the glass
3. Use distilled or RO water if your area has hard water (mineral deposits create a permanent film)
4. For large systems (10kW+), consider a solar panel cleaning robot for automated maintenance

Cause 2: Partial Shading — Even Small Shadows Are Devastating

This is the most misunderstood cause of low generation. Many homeowners think "it is just a small shadow from the water tank." But here is the technical reality:

Alert: In a series-connected string, one shaded panel can drag down the output of the entire string by 30-80%. A shadow on just 10% of one panel can reduce that entire string's output by half.

Common Shading Culprits in Pakistan

• Overhead water tanks: The most common offender on Pakistani rooftops
• Satellite dishes and TV antennas: Small but cast long shadows in morning and evening
• Neighboring building walls: Especially in dense urban areas of Karachi, Lahore, and Rawalpindi
• Growing trees: A tree that was small during installation may now shade panels
• Clothes drying lines: Yes, even wet clothes cast enough shadow to affect generation

The Fix

Check your roof at different times of day (8 AM, 12 PM, 4 PM) and note any shadows falling on panels. If relocation of the obstruction is not possible, ask your installer about bypass diodes or if half-cut cell panels can mitigate the issue. In severe cases, panel repositioning may be necessary.

Cause 3: Extreme Heat — Pakistan's Summer Penalty

This surprises most people: solar panels actually perform worse in extreme heat. They are rated at Standard Test Conditions (STC) of 25°C. Pakistani rooftops regularly exceed 55-65°C in summer.

Understanding Temperature Coefficient

Every solar panel has a temperature coefficient, typically -0.30% to -0.40% per degree Celsius above 25°C. Here is what this means in practice for a 10kW system:

The Fix

• Ensure at least 4-6 inches of gap between panels and roof surface for airflow (this alone can reduce panel temperature by 5-10°C)
• Consider N-Type TOPCon panels which have a better temperature coefficient (-0.29%) compared to older P-Type PERC panels (-0.35%)
• Accept that summer midday output of 75-85% of rated capacity is completely normal in Pakistan — your system is not faulty

Cause 4: Inverter Issues and Grid Voltage Problems

If your inverter is frequently tripping, showing error codes, or shutting down entirely, the panels may be generating power but the inverter cannot process it.

Common Inverter Problems in Pakistan

• Grid over-voltage: WAPDA voltage spikes above 270V cause on-grid inverters (Solis, Growatt, Huawei) to shut down for safety. This is common in areas with unstable transformers.
• Grid under-voltage: Voltage dropping below 170V during peak load hours causes the same issue.
• Inverter overheating: If your inverter is installed in direct sunlight or a sealed room, it will derate (reduce output) or shut down. Always install inverters in shaded, ventilated areas.
• MPPT voltage mismatch: If panels were wired incorrectly and the string voltage exceeds or falls outside the inverter's MPPT range, the inverter cannot optimize power extraction.

Alert: Never try to modify inverter voltage settings yourself. Incorrect anti-islanding settings can electrocute WAPDA line workers and are illegal. Always call a certified technician.

Cause 5: Wiring and Connection Degradation

Over 2-3 years, Pakistani weather (monsoon rains, extreme heat, dust storms) degrades exposed wiring. Check for:

• Loose MC4 connectors: These snap-fit connectors can work loose over time, causing arcing and power loss
• Corroded junction boxes: Moisture ingress into panel junction boxes causes resistance and hot spots
• Damaged DC cables: If your installer used cheap, non-UV-rated wires, the insulation may have cracked and degraded
• Tripped DC breaker: Check your DC breaker panel — a tripped breaker will cut off an entire string silently

Cause 6: Incorrect Installation Angle

Panels in Pakistan should be tilted at approximately 25-32 degrees (matching your latitude) and facing due south. If your panels were installed flat on a flat roof, you could be losing 10-15% of annual generation. Read our detailed guide on the best angle for solar panels in Pakistan.

Step-by-Step Troubleshooting Checklist

Before calling a technician and spending PKR 3,000-5,000 on a service call, work through this checklist:

1. Check the inverter display: Note any error codes and search them in your inverter manual (Solis, Growatt, and Huawei all have error code lookup in their apps)
2. Visually inspect panels from ground level: Look for obvious dirt, bird droppings, or debris
3. Check for shadows: Observe your roof at 10 AM, 12 PM, and 3 PM
4. Compare MPPT string outputs: If one string is producing significantly less, the issue is isolated to those panels or connections
5. Verify DC breakers are ON: Both at the panel array and at the inverter input
6. Check grid voltage: Use a multimeter at your main DB to verify WAPDA voltage is within 180V-250V range
7. Clean the panels: Do a thorough wash and measure generation the next day
8. Check inverter ventilation: Ensure nothing is blocking airflow around the inverter

If none of these steps resolve the issue, contact your installer or a certified solar technician with your inverter error codes and generation data ready.

When to Worry vs. When It Is Normal

Understanding "normal" generation helps you avoid unnecessary worry:

• Normal: 70-85% of rated capacity during peak summer (heat derating)
• Normal: 40-60% of rated capacity during cloudy winter days
• Normal: Zero generation during rain — on-grid systems may also shut down during grid outages
• Abnormal: Less than 60% of rated capacity at noon on a clear, sunny day after cleaning
• Abnormal: One MPPT string showing 50%+ less than another string
• Abnormal: Inverter tripping more than 3-4 times per day

Frequently Asked Questions