What is the Difference Between Mono and Poly Solar Panels?

The two big technologies in silicon-based solar are still MONO and POLY solar panels. Here at Solar Leading we stock both.

But what is the difference? and how do you know which one is best for you and your solar project?

Mono Crystalline Panels

The difference between mono and poly solar panels comes down to the cells that they are made from. The silicon in mono and poly cells undergo different manufacturing processes, making panels with slightly different performance characteristics. Understanding these differences will help you to choose the right panel for your project.

Mono crystalline panels (mono-si, mono) are made from silicon that has been ‘grown’ in a single crystal through the ‘Czochralski process’. The crystal is then trimmed, sliced into wafers and treated to form solar cells. Because of the shape of the crystal, mono cells tend to have distinctive ‘cut off corners’. Mono cells are easy to identify by these cut off corners and a smooth even black color.

The Mono panels that they make tend to be more efficient than poly panels but also more expensive. This means that if you take a mono panel and a poly panel of the same size and leave them in exactly the same light conditions, the mono panel will generate more power. However, that power will have cost you more per watt because the panel that generated it was more expensive.

This trade off in output and cost is often worth it in projects where space is restricted. For example, a home owner with a small roof might choose to use more expensive mono panels in order to squeeze the maximum power from his system in the long run.

Poly Crystalline Panels

Poly crystalline panels (poly-Si, poly) do not use silicon from a single crystal. Instead, silicon is taken from multiple sources, and subjected to intense heat and pressure to ‘cast’ a silicon ‘ingot’. This ingot can then be sliced into wafers and treated to make poly cells.

Poly cells used to be quite easy to recognize by their reflective ‘flaky’ blue surface but newer manufacturing processes are making them look more and more like mono panels every year.

The Poly solar panels they make have tended to be less efficient and less expensive than the same sized mono panels. This makes them better suited to installations where the most important consideration is not overall output but reduced cost per unit or accelerated return on investment. For example, many larger commercial and utility scale solar power plants use poly panels to produce electricity at a lower cost per watt in order to shorten the payback period of their system.

Poly panels have also tended to have slightly higher failure rates and slightly shorter life spans than mono panels, their output slowly degrading over a period of twenty-five to thirty years. This has generally been seen as an acceptable maintenance cost for larger installations. Solar investors realize that after twenty five years, their panels will have paid for themselves many times over in electricity generated and sold. Also, that far in the future, solar technology may well have advanced to the point where the replaced panels will be many times more efficient and less expensive than the originals.

We have put together this infographic to help you remember the difference:

Non-Crystalline Panels

As well as mono and poly, there are many other emerging pv technologies that are not made from silicon at all. These are often grouped together as non-crystalline or ‘thin film’ solar.

The technologies receiving the most attention at the moment are:

• Cadmium telluride (CdTe)
• Copper induim gallium selenide (CIGS)
• emerging ‘organic’ and ‘quantum’ technologies

These technologies hold great promise for the future. Some of them have proved more versatile and more tolerant to partial shading than either mono or poly in the lab. However, they are not yet able to compete with the availability, price or reliability of good old mono and poly solar panels. For this reason they have yet to be widely adopted in home, business or utility solar power systems.

So, are you using mono or poly panels? What was the deciding factor in your choice? Please let us know in the comments…