Buying solar panels is a long-game decision. The sticker price matters, but what really determines value is how well the panels keep producing electricity year after year. That’s where degradation rate comes in: it’s the slow, expected decline in a panel’s output as it ages. Two systems with the same wattage on day one can look very different after 15–25 years if one set of panels degrades faster than the other.

This article focuses on how to choose solar panels with low degradation rates—what degradation actually means, which technologies tend to perform better, what to look for in warranties and data sheets, and how to tell meaningful numbers from marketing. Along the way, you’ll also find a few practical tips that make the decision feel less like guessing and more like evaluating any other long-term investment.

What “degradation rate” actually means

Solar panel degradation is the gradual loss of a module’s ability to convert sunlight into electricity. Manufacturers usually express it as a percentage per year.

If a panel degrades 0.3% per year, it would retain roughly 92.8% of its original output after 25 years (approximate, compounding).

If it degrades 0.7% per year, it might retain around 84% after 25 years.

Those differences add up. Over decades, degradation affects:

your total lifetime energy production

payback period and long-term savings

how well your system matches future electricity needs (EVs, heat pumps, growing household use)

resale appeal if you sell the home with the system attached

Degradation is expected even in high-quality panels. The goal isn’t “zero degradation,” but lower and more predictable degradation.

The two degradation phases: early drop vs. long-term decline

A key detail that many buyers miss: panels often experience a small initial performance loss during the first hours/days of exposure to sunlight. After that, they settle into a slower long-term degradation slope.

Two terms you may see:

LID (Light-Induced Degradation)

Often associated with certain silicon types and older cell designs. It’s an early drop triggered by light exposure.

LeTID (Light and Elevated Temperature Induced Degradation)

A newer topic tied to some PERC cell structures under heat and light. Reputable manufacturers address this through process control and material choices.

When comparing panels, it’s helpful to know whether the “degradation rate” being advertised reflects only the long-term rate or also accounts for early losses. The best way to avoid confusion is to rely on the performance warranty curve, which typically includes both the first-year drop and the annual decline after that.

Start with the performance warranty (and know how to read it)

Manufacturers generally provide two warranties:

Product warranty (materials/workmanship): commonly 12–25 years

Performance warranty (output retention): commonly 25–30 years

For low degradation, you’re mainly looking at the performance warranty.

A typical warranty might say something like:

Year 1: guaranteed at 97%

Years 2–25: maximum degradation 0.5% per year

Year 25: guaranteed at 84.8%

A stronger warranty might read:

Year 1: 98%

Years 2–30: 0.25%–0.4% per year

Year 30: 88%–92% (depending on the curve)

What to compare across brands

When you’re shopping, line up these specifics:

First-year guaranteed output (%)

Annual degradation rate after year one (%)

Guaranteed output at year 25 and/or year 30 (%)

Whether it’s a linear warranty (straight-line decline) or a more complex curve

A practical rule of thumb

All else equal, panels that guarantee ~88% at 25 years are typically in the “lower degradation” tier. Panels that guarantee ~84–86% at 25 years can still be solid, but they’re not the best available in this category.

Also, read the fine print on what happens if the panel underperforms. Some warranties require you to ship the module, pay labor, or accept replacement at the manufacturer’s discretion. A strong warranty is useful, but it’s even better when the brand has a long track record and a presence in your region.

Look for third-party testing and long-term reliability signals

Degradation isn’t just a number; it’s a result of materials, manufacturing quality, and stress resistance. Since you can’t wait 25 years to find out, look for credible proxies.

Certifications that matter

IEC 61215 (design qualification and type approval)

IEC 61730 (safety qualification)

IEC 61701 (salt mist corrosion resistance) if you’re near the coast

IEC 62716 (ammonia corrosion resistance) if you’re in agricultural areas

Passing IEC tests is common, but some brands go beyond minimum compliance with extended internal testing or additional third-party validation.

Bankability and reliability reports

If you want a more professional lens, look for:

independent module reliability scorecards

industry “bankability” discussions (often used by large commercial buyers)

long-established manufacturers with consistent quality control

These sources don’t guarantee low degradation, but they reduce the odds of selecting a brand that looks good on paper and disappoints in the field.

Panel technology choices that influence degradation

Different cell architectures and materials tend to age differently. Here’s a buyer-friendly breakdown.

Monocrystalline vs. polycrystalline

Most modern residential systems use monocrystalline panels. Polycrystalline is less common today and doesn’t necessarily degrade drastically faster, but top-tier low-degradation offerings are typically mono.

N-type vs. P-type cells (important)

This is one of the more meaningful distinctions for degradation behavior.

P-type (PERC) panels dominated the market for years. Many are excellent, but some PERC designs can be more sensitive to certain degradation modes if manufacturing controls are weaker.

N-type panels (including TOPCon and HJT) generally have better resistance to LID, and often come with stronger performance warranty terms.

If low degradation is a priority and your budget allows it, N-type modules are worth prioritizing.

HJT, TOPCon, and IBC—what to know

HJT (Heterojunction): known for strong temperature performance and often very competitive degradation warranties. Typically premium-priced.

TOPCon: rapidly growing; many brands offer solid degradation specs and strong value.

IBC (Interdigitated Back Contact): efficient and premium; often paired with excellent warranty terms. Availability varies.

You don’t need to memorize acronyms, but you can use them as signals. When you see an N-type module with a 30-year performance warranty and an annual degradation rate around 0.25–0.4%, you’re likely in the right neighborhood.

Pay attention to temperature coefficient and real operating conditions

Degradation is long-term aging, but heat affects daily performance and can influence stress over time. Panels are tested at 25°C (77°F) in labs, while your roof might be far hotter.

Look for the temperature coefficient of Pmax, usually written like:

-0.29%/°C (better)

-0.35%/°C (more typical)

-0.40%/°C (less favorable)

A better (less negative) coefficient means the panel loses less output as temperature rises. It doesn’t directly equal lower degradation, but panels engineered for high-temperature performance often reflect higher-end designs and material quality.

Also consider:

Roof ventilation and mounting height (airflow helps)

Local climate (desert heat, humid tropics, freeze-thaw cycles)

Installation quality (cable management, grounding, avoiding hot spots)

Degradation isn’t only “natural aging”: avoid the common causes of accelerated decline

Some performance loss happens with time, but accelerated degradation can be triggered by environmental or electrical stress. Choosing the right panel helps, and so does choosing the right installer.

PID resistance (Potential Induced Degradation)

PID can occur when voltage potential causes leakage currents that reduce output, often in humid environments or high system voltages. Many modern panels are PID-resistant, but it’s still worth confirming in the spec sheet.

Look for mentions such as:

“PID resistant”

IEC testing related to PID (some manufacturers disclose this)

Hot spots and microcracks

Microcracks can occur during shipping, handling, or installation. They may not show up immediately but can worsen with thermal cycling.

To reduce the risk:

buy from an installer with careful handling practices

request transport and storage best practices

consider panels known for strong mechanical load ratings and quality control

Moisture ingress and backsheet quality

Water vapor getting into a module can cause corrosion and performance loss. This is where manufacturer quality and materials matter, and why brand track record is relevant.

Interpreting the data sheet like a buyer, not an engineer

Solar panel spec sheets can feel dense. For low degradation selection, focus on a short list of items:

Performance warranty details

First-year retention + annual rate + year 25/30 guarantee.

Cell type

N-type vs P-type, and whether it’s TOPCon/HJT/IBC.

Temperature coefficient (Pmax)

Lower magnitude is better.

Mechanical load ratings

Higher snow/wind load ratings can mean better resilience, depending on design.

Degradation-related claims

PID resistance, anti-LID statements, and any third-party testing references.

If a manufacturer advertises “low degradation” but provides vague warranty language or unclear numbers, treat that as a caution sign. The best brands make it easy to verify.

Compare panels by lifetime energy, not just wattage

It’s tempting to buy based on the biggest watt number. But for long-term value, you want expected lifetime production.

A simple way to compare:

Take system size (kW)

Multiply by estimated annual production (kWh/year)

Apply degradation assumptions over time

Installers can model this in software, but you can also ask for two proposals:

standard panel option

low-degradation panel option

Then compare:

projected kWh at year 10, 20, 25

cost difference

added kWh gained over the system life

implied cost per extra kWh

Sometimes premium low-degradation panels cost more than the added production is “worth” financially. Other times, the gap is small and it makes sense to pay for better longevity and warranty strength.

Don’t ignore the installer: workmanship affects long-term performance

Even the best panel can underperform if the system is installed poorly. A few installer-related factors that connect to degradation and long-term output:

Proper clamping zones (incorrect clamping can stress the frame and glass)

Correct torque specs for fasteners

Avoiding cable shading and poor wire routing that creates hot spots

Roof penetration sealing to prevent water issues around mounts

Inverter and optimizer selection matched to panel electrical characteristics

If you’re serious about long-term performance, ask your installer:

how they handle panels during transport and staging

whether they use microinverters/optimizers (helpful for shade; not a degradation fix, but can preserve output)

what monitoring platform you’ll get (so you can spot problems early)

Monitoring is underrated: catching a failing connection or underperforming string early can save years of lost production.

Quick checklist for choosing low-degradation solar panels

Use this as a practical filter when comparing options:

Performance warranty: at least 25 years; check year-25 guaranteed output

Annual degradation rate: aim for 0.25%–0.45% after year one when possible

Cell technology: prioritize N-type if budget allows

Temperature coefficient: choose a strong value for hot climates

PID resistance: confirmed in documentation

Brand track record: consistent manufacturing history, good warranty execution

Installer quality: documented handling, strong workmanship warranty, good monitoring

If two panels look similar, the deciding factor often becomes warranty clarity and manufacturer reputation. A low degradation number is only as good as the company standing behind it.