Understanding PID in Solar Panels – Causes, Effects, and Prevention

Have you ever wondered why some solar systems lose performance much faster than expected — even when everything looks fine from the outside? The culprit is often something called Potential Induced Degradation (PID), a silent efficiency killer that can reduce your panel output by up to 30% over time.

In this article, we’ll explain what PID really is, why it happens, and how modern inverter technology and installation methods — including microinverters — can help eliminate it completely.

What Exactly is Potential Induced Degradation (PID)?

PID is a type of performance loss that occurs when there is a high voltage potential difference between a solar cell and its frame or grounding element. Over time, this voltage difference causes charged ions, usually sodium (Na⁺) from the glass or encapsulant, to migrate into the solar cell. This ion migration leads to leakage currents, disrupting the internal electric field and reducing the cell’s power output.

In simple terms — PID happens when high system voltage and grounding imbalances cause unwanted electrical stress on your panels, slowly damaging them from within.

What Causes PID in Solar Systems?

• High negative voltage to ground: Usually occurs in string inverter systems where one side of the string operates at high negative potential relative to the grounded frame.
• Humidity and temperature: Moisture increases conductivity in the glass and encapsulant, accelerating ion migration.
• Panel construction quality: Low-quality encapsulants or glass allow sodium ions to move more easily.
• System grounding design: Improper grounding increases potential difference, worsening PID effects.

How Does PID Affect Performance?

PID doesn’t cause visible damage to the panel, which makes it tricky to detect early. However, its effects are significant:

• Gradual drop in power output (up to 30% in severe cases)
• Reduced open-circuit voltage (Voc) of the modules
• Uneven string performance (some modules performing poorly)
• Hotspots and faster cell degradation due to leakage currents and local heating

If PID goes unchecked, it can drastically reduce system performance and accelerate module aging, leading to a lower ROI for your solar investment.

How to Detect PID in Your Solar Plant

Early detection is key. PID can be identified through:

• Infrared (IR) thermography to locate hot spots
• IV curve tracing for performance drop analysis
• Module-level monitoring (in microinverter systems)
• Periodic power output comparison with expected generation benchmarks

Many advanced inverters can also provide PID detection alerts through their monitoring platforms.

Methods to Prevent and Eliminate PID

1. Use Microinverters

The most effective modern solution is to use microinverters. Unlike string inverters, where panels are connected in long series circuits operating at high DC voltage (600–1000V), microinverters convert DC to AC right at each panel, keeping the voltage low (typically below 60V).

With such low DC potential and no large negative voltage to ground, the electrical stress that causes PID is effectively eliminated. This not only prevents PID but also improves safety and reliability, making microinverters ideal for residential and commercial systems where long life and stability matter most.

2. Use PID-Free or PID-Resistant Modules

Many top-tier manufacturers now offer PID-resistant modules that use special glass, encapsulants, and cell coatings to block sodium ion migration. Choosing certified PID-resistant panels can minimize long-term degradation.

3. Install a PID Recovery Unit

For systems already showing PID symptoms, PID recovery units (or “anti-PID boxes”) can be installed. These devices apply a small reverse voltage at night to neutralize the ion migration, helping restore module performance over time.

4. Maintain Proper Grounding

Ensure that the inverter, array frame, and negative pole of the system are properly grounded. This minimizes potential difference between the cells and the frame, reducing stress that can cause PID.

5. Control Temperature and Humidity

In hot and humid climates, PID risk increases. Regular cleaning, sufficient module spacing, and ventilation can help lower operating temperature and surface moisture — further reducing the risk.

Why Microinverters Are the Future

In addition to eliminating PID, microinverters offer several other benefits:

• Each panel works independently — no mismatch losses
• Real-time monitoring at module level
• Enhanced safety with lower DC voltage
• Scalability for future system expansion

As more solar owners demand transparency, reliability, and long-term returns, microinverter-based systems are quickly becoming the preferred choice — ensuring you never have to worry about silent degradation like PID again.

Conclusion

Potential Induced Degradation is a serious but preventable issue. With better materials, grounding design, and especially with the adoption of microinverters, you can completely eliminate PID-related risks. For anyone planning a rooftop solar system, understanding PID and choosing the right technology can make the difference between a system that lasts decades — and one that underperforms within a few years.

PID-free solar systems = higher output, longer life, and peace of mind.