Photovoltaic Modules Compared: Technology, Types & Selection

Photovoltaic modules are the heart of every PV system: their cell technology, power class and build quality determine yield and lifespan. This guide explains how modules are built, the module types, today’s cell technologies and the figures that really matter when you compare them. How the right modules are planned and installed in practice is shown in our overview of solar systems in Hanover.

What Makes Up a Photovoltaic Module?

Photovoltaic modules, often called solar panels, convert sunlight directly into direct current. This happens in solar cells made of semiconductor material, almost always silicon. An inverter turns it into alternating current for your home, and a battery can store it for the evening.

A module consists of several layers:

• Solar cells: generate the electricity and largely determine the efficiency.
• Front glass: tempered solar glass protects the cells from hail, snow and weather.
• Encapsulation: a film embeds the cells, insulates them and keeps moisture out.
• Rear side: either a plastic backsheet (glass-foil) or a second pane of glass (glass-glass).
• Frame and junction box: the aluminium frame provides stability and mounting points, the junction box with bypass diodes handles the current.

Module Types at a Glance: Monocrystalline, Polycrystalline, Thin-Film

• Monocrystalline modules: cells made from a single silicon crystal, high efficiency and a uniform dark look. They are the standard today: according to the Fraunhofer ISE Photovoltaics Report, the global PV market is dominated by crystalline silicon and n-type TOPCon cells.
• Polycrystalline modules: cells made of many small crystals, recognisable by their bluish texture. Their efficiency is clearly lower, and they are practically no longer offered for new rooftop systems.
• Thin-film modules: very thin semiconductor layers on glass or film. They are lighter but less efficient and need much more space. For residential roofs they are a niche product.

For most single-family homes the answer is therefore: monocrystalline modules with modern n-type cell technology. The next section explains what that means.

Cell Technologies: From PERC to TOPCon, HJT and Back-Contact

Within monocrystalline modules, cell technology has developed rapidly in recent years:

• PERC: long the standard. A passivated rear side gets more light out of the cell. In new modules, PERC has largely been replaced by n-type cells.
• TOPCon: today’s most widespread technology in new modules. It reaches higher efficiencies than PERC, ages more slowly and is attractively priced. One example is JA Solar’s DeepBlue 4.0 Pro series.
• HJT (heterojunction): combines crystalline and amorphous silicon. Very good behaviour in heat, but less common and usually more expensive.
• Back-contact (ABC, HPBC): all electrical contacts are on the rear. This gives the highest efficiencies, very good tolerance of partial shading and a clean look. Examples are AIKO (ABC) and Longi (HPBC).

Two designs are found almost everywhere today: half-cut cells (halved cells reduce losses and help with partial shading) and bifacial modules, which also capture light on the rear. Bifacial modules gain most on bright, reflective surfaces such as gravel or white flat roofs; on a normal pitched roof the extra yield is small.

Glass-Glass or Glass-Foil: Which Build Is Better?

In glass-foil modules a plastic backsheet protects the rear. They are lighter and cheaper and perfectly adequate for most roofs.

Glass-glass modules also have a pane of glass on the back. This makes them particularly resistant to moisture and micro-cracks, they age more slowly and often come with longer warranties. The downside: they are heavier. On a normal residential roof this is rarely a problem; on light hall roofs the structure has to be checked.

Our recommendation: if you want the longest possible lifespan or plan bifacial modules on a flat roof, glass-glass is a good choice. For a typical single-family home, a high-quality glass-foil module is just as solid an option.

Efficiency, Output and How to Read a Datasheet

When comparing photovoltaic modules, these datasheet figures help:

• Rated power (Wp): output under standard test conditions. Modern modules for residential roofs are around 430 to 450 Wp and about 1.9 to 2 m² in size.
• Efficiency (%): how much of the sunlight is converted into electricity. According to manufacturer datasheets, current premium modules reach about 22.5 % (TOPCon) to over 24 % (back-contact). Higher efficiency pays off especially when roof space is limited.
• Power tolerance: look for a positive tolerance, i.e. the module delivers at least its rated output.
• Temperature coefficient (%/°C): how much output drops in heat. The closer to zero, the better. According to their datasheets, the back-contact modules from AIKO and Longi are around −0.26 %/°C, JA Solar’s TOPCon module around −0.29 %/°C.
• Dimensions and weight: important for the roof layout and the structure.

Quality, Warranty and Lifespan

High-quality photovoltaic modules last 25 to 30 years and often longer. There are two warranties:

• Product warranty: covers material and manufacturing defects. Premium modules usually offer 25 years today.
• Performance warranty: guarantees a minimum output over the years. For the modules we install, the manufacturers state 30 years with around 88 to 89 % remaining output.

Also check for certification to IEC 61215 (durability and ageing) and IEC 61730 (electrical safety), and choose an established manufacturer that can still honour the warranty in 20 years. We state the exact warranty values for your module in the written quote, as they can vary by variant.

How Many Modules Do You Need and What Do They Cost?

With modern modules, each kWp of system output needs around 2 to 3 modules and about 4.5 to 5.5 m² of roof. A 10 kWp system therefore consists of around 22 to 24 modules on about 45 to 55 m². How to find the right size for your consumption is explained in how many solar panels a house needs.

The modules are only part of the total cost: inverter, mounting system, cabling, installation and registration come on top. For a complete system our guide price is about €1,450–1,750 per kWp, so a 10 kWp system costs about €14,500–17,500 without storage. Systems on residential buildings are taxed at 0 % VAT. There is no separate subsidy just for modules; which benefits you can use is shown on our page solar subsidies in Germany. All cost items are listed under solar panel costs.

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Which Photovoltaic Modules Do We Install?

As a specialist company from Hanover, we deliberately work with a small selection that has proven itself on real roofs: modules from AIKO, JA Solar and Longi, combined with Fronius inverters, BYD batteries and K2 Systems mounting. Which module suits which roof, with efficiency, warranty and our recommendation per use case, is compared in detail under best solar modules compared.

A good module alone does not make a good system: modules, inverter and stringing have to match. By the way: during a power cut, a normal PV system switches off for safety reasons. If you want power during an outage, you need a battery with a backup power function.

Conclusion: How to Find the Right Module

For most roofs, monocrystalline n-type modules are the right choice: TOPCon as the proven value standard, back-contact when space is tight or the roof is partly shaded, and glass-glass when you want maximum durability. Compare efficiency, temperature coefficient and warranties, not just the price per module. We advise you honestly which modules suit your roof and budget and install them with our own certified technicians, with a fixed-price guarantee and a 30/70 payment model.

Request a free, no-obligation quote, by phone on +49 511 3360603 or via WhatsApp on +49 176 2399 8536.