Polycrystalline solar panels are one of the major types of PV systems available in the UK.
Solar panels have become crucial in the shift towards sustainable living and a cleaner, energy-independent future.
Adoption continues to climb in the UK, with official statistics showing 17.6 GW of solar capacity in the UK across over 1.7 million installations as of the end of December 2024.
If you’re considering harnessing the sun’s power to power your home, learning more about polycrystalline solar panels can ensure you make an informed decision.
Quick Takeaways:
- Manufacturers make polycrystalline solar panels by melting multiple silicon fragments to form photovoltaic cells.
- They’re less efficient than monocrystalline panels
- They’re also cheaper and more environmentally friendly since they produce less silicon waste
- The lower efficiency is caused by their multi-crystal structure, less uniformity, lower light absorption and higher internal resistance
What Are Polycrystalline Solar Panels?
Polycrystalline solar panels are photovoltaic (PV) panels made from multiple silicon crystals. They have a distinct blue, speckled appearance, and you can still see them in some older solar panel systems across the country.
Data from the Microgeneration Certification Scheme (MCS) shows that popularity has shifted from polycrystalline to monocrystalline solar cells since 2019. Monocrystalline panels are now the more dominant technology thanks to advances in production and cost reductions.
How Do They Work?
Polycrystalline solar panels use the photovoltaic effect to generate electricity by converting sunlight into usable energy.
Each panel comprises multiple silicon crystal fragments, which are melted together to form a single solar cell. When sunlight strikes these silicon cells, the electrons get excited, causing them to move and create an electric current.
This electricity starts as direct current (DC), but the inverter changes it to alternating current (AC) that can power your home or business. You can use the AC electricity immediately, store it in a battery or send it to the national grid if there’s an excess.
Although they’re slightly less efficient than their monocrystalline alternatives, polycrystalline panels still perform well in moderate sunlight.
They produce the most energy on clear, sunny days but continue working even when the sky is overcast.
How Are Polycrystalline Solar Panels Made?
Manufacturers make polycrystalline solar panels by melting multiple silicon fragments to form photovoltaic cells, making production more cost-effective.
- Silicon Purification: Raw silicon is extracted from quartz and refined to remove impurities, ensuring it can efficiently conduct electricity.
- Melting and Moulding: The purified silicon is melted and poured into square-shaped moulds, where it cools and solidifies into large ingots containing multiple crystals.
- Slicing into Wafers: Diamond-coated saws cut the solidified silicon ingots into thin wafers. These wafers form the base of each solar cell.
- Doping and Coating: The wafers are treated with phosphorus and boron to improve electrical conductivity, creating an electric field. An anti-reflective coating is applied to enhance light absorption.
- Assembly into Solar Cells: Metal conductors are printed onto the wafers to form electrical pathways, turning them into individual solar cells.
- Panel Assembly: Multiple cells are wired together and encased in a protective glass layer before being framed and fitted with a back sheet.
The finished panels are then tested for efficiency and durability.
What Are the Advantages of Polycrystalline Solar Panels?
Lower Cost
Polycrystalline panels are more budget-friendly than monocrystalline alternatives. Their simpler manufacturing process tends to lower their upfront cost while delivering reliable performance.
Good Efficiency for the Price
Although they are less efficient than monocrystalline panels, modern polycrystalline technology has significantly improved.
Many models now achieve efficiencies between 15% and 18%, making them a solid choice for households looking to save money without sacrificing too much performance.
Environmentally Friendly Production
The manufacturing process of polycrystalline panels produces less silicon waste than monocrystalline panels, making them a more sustainable choice. It also requires less energy, which helps reduce the overall environmental impact.
Durable and Long-Lasting
Polycrystalline panels can withstand various weather conditions, from heavy rain and strong winds to occasional snowfall. Most manufacturers offer 20 to 25-year warranties, and they often continue to generate electricity beyond that timeframe.
Good Performance in Moderate Sunlight
While they may not be the best for extremely low-light conditions, polycrystalline panels perform well in the UK’s moderate sunlight levels, making them a practical choice for residential and commercial installations.
What Are the Disadvantages of Polycrystalline Solar Panels
Although polycrystalline panels offer great value, they aren’t perfect. Here are some drawbacks to consider:
Lower Efficiency Compared to Monocrystalline
Monocrystalline panels are typically more efficient, often reaching 20% or more. This means polycrystalline panels need more space to generate the same power, which could be a limiting factor if you have a small roof.
Slightly Shorter Lifespan
Although polycrystalline panels last for decades, they tend to have a slightly shorter lifespan than monocrystalline panels due to their structure. Over time, they may degrade slightly faster, reducing energy production.
Less Effective in Low-Light Conditions
Monocrystalline panels perform better in shaded or low-light conditions, making them better for properties in areas with frequent cloudy days or shading from trees or buildings.
How Do Polycrystalline Panels Compare to Other Types?
Polycrystalline vs. Monocrystalline Solar Panels
The structural difference of polycrystalline panels impacts efficiency, cost, and performance.
| Feature | Polycrystalline | Monocrystalline |
| Cost | More affordable | More expensive |
| Efficiency | 15-18% | 18-22% |
| Lifespan | 20-25 years | 25-30 years |
| Low-light performance | Moderate | Better |
| Appearance | Blue, speckled | Black, uniform |
| Space Requirements | Requires more space | More efficient per square metre |
Polycrystalline vs. Thin-Film Solar Panels
Thin-film panels use different materials, such as cadmium telluride (CdTe) or amorphous silicon, making them more flexible and lightweight than crystalline panels.
| Feature | Polycrystalline | Monocrystalline |
| Cost | Moderate | Lower |
| Efficiency | 15-18% | 10-12% |
| Durability | High | Moderate |
| Weight | Heavier | Lighter |
| Installation | Standard | Flexible |
Why Do Polycrystalline Solar Panels Have Lower Efficiency Than Monocrystalline?
Multi-Crystal Structure
The manufacturing process of polycrystalline panels creates a multi-crystal structure. It causes small gaps and grain boundaries between the crystals, disrupting the flow of electrons.
In contrast, monocrystalline panels use a single, continuous silicon crystal, allowing electrons to move more freely and generate electricity more efficiently.
Less Uniformity in Silicon Composition
The presence of multiple crystals results in structural inconsistencies within polycrystalline solar cells. These variations can lead to minor defects that slightly reduce energy conversion efficiency.
Monocrystalline panels, on the other hand, have a highly uniform composition, improving performance.
Lower Light Absorption
Polycrystalline panels have a distinct blue hue due to their crystalline structure reflecting more sunlight. Monocrystalline panels, with their darker black appearance, absorb more light and convert a greater portion into electricity.
This difference is particularly noticeable in low-light or cloudy conditions, where monocrystalline panels perform better.
Higher Internal Resistance
The grain boundaries between multiple silicon crystals in polycrystalline cells create higher electrical resistance.
This means some energy is lost as heat instead of being converted into usable electricity. Monocrystalline panels have a more efficient electrical path, reducing resistance and improving overall output.
Space Between Crystals Reduces Conductivity
Since polycrystalline cells contain multiple silicon fragments, the material has less direct conductivity. This results in a slight loss of efficiency compared to monocrystalline panels, where electrons travel more efficiently through a single-crystal structure.
How Suitable Are Polycrystalline Solar Panels for Different Applications?
Polycrystalline solar panels are widely used across domestic, industrial and commercial sectors due to their cost-effectiveness and reliable performance. While they may not be the most efficient option, they offer a solid balance of affordability and durability, making them suitable for various applications.
Residential Use
Polycrystalline panels are a practical choice if you’re looking for an affordable way to reduce your electricity bills and reliance on the grid. They work well for:
- Detached and semi-detached homes with ample roof space.
- Solar panel arrays in gardens if roof space is limited.
- Battery storage systems to maximise self-consumption.
Since their efficiency is slightly lower than monocrystalline panels, they are best suited for properties with enough roof area to install more panels. They’re a budget-friendly choice for those with more installation space.
Commercial and Industrial Applications
Businesses and factories can benefit from polycrystalline panels, particularly those with large rooftops or unused land. These panels offer:
- A lower upfront investment than monocrystalline panels.
- Scalability, making them ideal for warehouses, offices, and farms.
- Long-term savings on energy bills with minimal maintenance.
Off-grid and Rural Installations
Polycrystalline panels are commonly used in off-grid setups, especially if you live in a rural location with limited access to electricity. They are suitable for:
- Providing power for lighting, irrigation, and equipment in farms and agricultural buildings
- Remote cabins and holiday homes with solar battery storage
Large-Scale Solar Farms
Due to their lower cost per panel, polycrystalline panels are often used in solar farms, where land availability makes up for their lower efficiency.
These farms feed electricity into the grid or power local communities. Polycrystalline panels balance affordability, efficiency, and durability, making them a practical choice for large-scale solar farms.
What Factors Should You Consider When Choosing Polycrystalline Solar Panels?
Selecting the right polycrystalline solar panels involves evaluating various factors to ensure they meet your energy needs, budget, and installation requirements.
Such considerations allow you to make an informed decision and select polycrystalline panels that offer the best balance of affordability, efficiency, and long-term reliability.
Efficiency Rating
Polycrystalline panels typically have efficiency levels between 15% and 18%, meaning they convert this percentage of sunlight into usable electricity. Higher-efficiency panels generate more power in less space, which is crucial if you have limited roof space.
Power Output
The power output of polycrystalline panels is measured in watts (W), with most residential models ranging from 250W to 400W per panel. A higher wattage panel will produce more electricity, reducing the number of panels needed.
Cost vs. Budget
The average cost of one polycrystalline panel can range from £225 to £250. They’re more affordable than monocrystalline options, but prices vary based on brand, efficiency, and warranty length. Consider the total system cost, including inverters, mounting equipment, and installation.
Aesthetic Considerations
Polycrystalline panels have a distinct blue colour, which may not blend as seamlessly with darker rooftops compared to black monocrystalline panels. If appearance is a priority, this might influence your decision.
How does the temperature coefficient of polycrystalline compare to that of monocrystalline solar panels?
The temperature coefficient of a solar panel measures how much its efficiency decreases as temperatures rise. The UK government’s Home Energy Model (HEM) notes that the temperature coefficient of PV modules typically ranges from -0.3% / °C to -0.5% / °C.
Polycrystalline Solar Panels
Polycrystalline panels typically have a temperature coefficient between -0.4% and -0.5% per degree Celsius.
This means that for every degree above 25°C (standard test conditions), the panel loses 0.4% to 0.5% of its efficiency. For example, at 35°C, a polycrystalline panel may lose 4% to 5% of its power output.
Monocrystalline Solar Panels
Monocrystalline panels usually have a lower temperature coefficient, around -0.3% to -0.4% per degree Celsius. This makes them more efficient in hot weather compared to polycrystalline panels.
If temperatures rise to 35°C, monocrystalline panels may lose 3% to 4% of their efficiency, slightly outperforming polycrystalline options.
Why Does This Matter?
Knowing a solar panel’s temperature coefficient is crucial since solar panels become less effective in high temperatures. The lower the temperature coefficient, the better a panel maintains its performance in hot conditions.
- Monocrystalline panels are a better choice in hot climates as they retain more efficiency.
- The difference is less significant in cooler climates like the UK, as temperatures rarely stay high for long periods.
While polycrystalline panels are more affordable, monocrystalline panels provide better temperature resilience, making them the preferred choice for high-temperature environments or efficiency-focused installations.
However, for many UK homeowners, the cost savings of polycrystalline panels outweigh the minor performance loss in hot weather.
Final Thoughts
Polycrystalline solar panels are an affordable and reliable choice for UK homes. They provide a good balance of efficiency and cost, making them ideal if you want solar energy without breaking the bank.
Monocrystalline panels may be a better option if you have limited roof space due to their higher efficiency. However, if you have ample space and want a cost-effective way to reduce energy bills, polycrystalline panels are a solid investment.
Sources and References
- https://assets.publishing.service.gov.uk/media/65783fe30467eb001355f5a0/hem-tp-18-pv-generation-and-self-consumption.pdf
- https://www.gov.uk/government/statistics/solar-photovoltaics-deployment
- https://mcsfoundation.org.uk/wp-content/uploads/2024/11/MCSF-Solar-PV-VS-Heat-Pump-Report-Final.pdf