Types of Solar Panels: How They Work and Compare
Learn how monocrystalline, polycrystalline, and thin-film solar panels are made, their efficiency, heat behavior, and where differences matter.
Solar panels convert sunlight into electricity using photovoltaic cells. The type of cell determines how efficiently that conversion happens, how the panel behaves in heat and low light, and how it degrades over time. The three main types are monocrystalline, polycrystalline, and thin film. Each is made differently, and those differences explain most of their performance characteristics.
Monocrystalline Panels
Monocrystalline cells are cut from a single crystal of silicon. The silicon is grown into a cylindrical ingot, then sliced into thin wafers. Because the crystal structure is continuous, electrons move more freely, giving these cells the highest efficiency of the three types. Typical efficiencies range from 17% to 22% under standard test conditions.
Monocrystalline cells are usually black or dark blue, with rounded corners because of the cylindrical ingot. They are slightly more expensive to produce, but they generate more power per square metre, so fewer panels are needed for a given output.
In hot conditions, monocrystalline panels lose efficiency, but less than polycrystalline. Their temperature coefficient—the percentage of power lost per degree Celsius above 25°C—is typically around -0.3% to -0.4% per °C. That means on a 40°C day, a panel might lose 4.5% to 6% of its rated power.
In low light, such as cloudy days or early morning, monocrystalline panels perform better than polycrystalline because the higher purity silicon responds more effectively to diffuse light.
Polycrystalline Panels
Polycrystalline cells are made by melting silicon and pouring it into a square mould, where it cools and solidifies into multiple crystals. The boundaries between crystals impede electron flow, so efficiency is lower—typically 15% to 17%.
The cells have a distinctive blue, speckled appearance. They are cheaper to manufacture because the process is simpler and wastes less silicon.
Polycrystalline panels have a higher temperature coefficient, around -0.4% to -0.5% per °C, so they lose more efficiency in heat. In a hot climate, the gap between mono and poly performance widens.
In low light, polycrystalline panels are less effective than monocrystalline, but they still produce power. The difference is noticeable on overcast days, but for many installations the total annual energy difference is small—often within a few percent.
Thin-Film Panels
Thin-film panels are made by depositing a thin layer of photovoltaic material onto a substrate such as glass, metal, or plastic. The materials include cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and amorphous silicon (a-Si).
Thin-film panels are much lighter and more flexible than crystalline panels. They can be made into large sheets, which reduces installation labour. However, their efficiency is lower—typically 10% to 13% for CdTe, and even lower for a-Si.
Thin-film panels behave differently in heat and low light. Amorphous silicon, for example, has a lower temperature coefficient, meaning it loses less efficiency in heat than crystalline panels. Some thin-film types also perform better in low light and high temperatures, which can make them suitable for hot climates despite their lower efficiency.
However, thin-film panels degrade faster than crystalline panels. Typical annual degradation is around 0.5% to 1% per year, compared to 0.3% to 0.5% for crystalline. That means after 25 years, a thin-film panel might produce 75% to 85% of its original power, while a crystalline panel might produce 85% to 92%.
Thin-film panels also require more roof space for the same output, which can be a limiting factor on residential roofs.
Comparison Table
The table below summarises the key properties. The last column notes when a property does not apply or is not the deciding factor.
| Property | Monocrystalline | Polycrystalline | Thin Film | When It Does NOT Apply |
|---|---|---|---|---|
| Efficiency (STC) | 17%–22% | 15%–17% | 10%–13% | Not the only factor; space may be ample |
| Temperature coefficient | -0.3% to -0.4% per °C | -0.4% to -0.5% per °C | Varies; a-Si lower | Not critical in cool climates |
| Low-light performance | Good | Moderate | Varies; some good | Not critical if sun is strong |
| Degradation per year | 0.3%–0.5% | 0.3%–0.5% | 0.5%–1% | Not critical for short-term installations |
| Space needed for 1 kW | ~5–6 m² | ~6–7 m² | ~8–10 m² | Not critical on large ground mounts |
| Cost | Higher | Lower | Lowest per watt | Not relevant when comparing only performance |
What People Get Wrong
A common mistake is assuming that the highest efficiency panel is always the best choice. That is a natural assumption because efficiency is a simple number, but it ignores the trade-offs. For example, if roof space is not a constraint, a lower-efficiency polycrystalline panel might produce nearly the same annual energy at a lower cost. The difference in efficiency does not translate directly to a difference in energy output—it translates to a difference in area.
Another mistake is believing that monocrystalline panels are always better in hot weather. While they do have a lower temperature coefficient than polycrystalline, the difference is small. In a real installation, the mounting height and airflow under the panel often matter more than the cell type. A well-ventilated polycrystalline panel can outperform a poorly ventilated monocrystalline one.
A third mistake is assuming thin-film panels are obsolete. They are not; they have niche applications where their flexibility and light weight are advantages, such as on curved surfaces or large commercial roofs with ample space. The lower efficiency is a trade-off, not a disqualifier.
What Actually Matters
For most residential installations, the choice between monocrystalline and polycrystalline has a small impact on total energy production. The bigger factors are the orientation and tilt of the roof, shading, and the quality of the installation. A 1% difference in efficiency is often less important than a 5% difference in shading.
Thin-film panels are worth considering only when space is not a constraint and the lower temperature coefficient is beneficial, such as in very hot climates. But the faster degradation means the long-term output may be lower.
A Note on Local Rules
Net metering, interconnection, export compensation, permitting, and incentives are set by state and by utility, and they change. Check with the local utility and authority having jurisdiction before making decisions. Do not assume that rules from one place apply elsewhere.
Safety Warning
A PV array produces dangerous DC voltage whenever light hits it, and it cannot be switched off at the panel. Do not open a combiner box, probe a live string, or disconnect an energised connector. Work on the DC side is for qualified personnel. Roof work and mains connection are licensed trades.
Common questions
What are the different types of solar panels?
The three main types are monocrystalline, polycrystalline, and thin film. Monocrystalline is made from a single silicon crystal, polycrystalline from multiple crystals, and thin film from a thin layer of photovoltaic material. They differ in efficiency, cost, and performance in heat and low light.
Which is better: monocrystalline or polycrystalline?
Monocrystalline panels are more efficient and perform slightly better in heat and low light, but they cost more. Polycrystalline panels are cheaper and slightly less efficient. The 'better' choice depends on your roof space, budget, and climate. In many cases, the difference in annual energy is small.
Are thin film solar panels any good?
Thin film panels have lower efficiency but are lighter and more flexible. They may perform better in high temperatures and low light, but they degrade faster and need more space. They are a good option when space is not limited and flexibility is important.
Do solar panels work on cloudy days?
Yes, but at reduced output. Monocrystalline panels have the best low-light performance, followed by polycrystalline and then thin film. The exact output depends on the thickness of cloud cover and the panel type.
How long do solar panels last?
Most panels are warranted for 25 years, but they continue to produce power beyond that. Crystalline panels typically degrade 0.3% to 0.5% per year, while thin film degrades faster at 0.5% to 1% per year. After 25 years, a crystalline panel might still produce over 85% of its original power.
Read next
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