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The Panels or “modules” are the thing that people think of first when considering a solar PV system. The panel is responsible for converting sunlight into electricity and under normal circumstances can be expected to perform efficiently for well over 25 years. There are many different manufacturers, types and sizes to choose from so the aim of this guide is to give you the essential information you need to make an informed decision.

Manufacturers

There are hundreds of PV panel manufacturers worldwide. Some of them will make every single component of the panel, starting with ingots of silicon which they cut into wafers which in turn make up the cells which ultimately are mounted in a frame to become a panel.  Other manufacturers will buy in the cells and make their panels that way. China and Germany are the two main manufacturing centres but panels are also made in countries as diverse as England, India and Jordan. It is impossible to judge a panel purely on the basis of its country of origin. Some of the world’s most advanced engineering facilities are in China but at the same time German engineering is world-renowned.

Any manufacturer that has had their panels accredited under the MCS scheme to be sold in the UK has been independently assessed to ensure that their panels meet the UK requirements and are suitable for sale here.

There are of course some well known names that have captured a good portion of market share, but it is interesting to note that the top selling products in Europe are different from the top sellers in America and the UK market is different again. It is important to remember that a best seller in any market may well be the company with the biggest marketing budget in that market!

Mono V Poly

Solar PV panels are grouped into two main types; mono-crystalline and poly-crystalline.  This refers to the manufacturing process by which the wafers which make up the panel are made. Mono panels use wafers that have been made from the same crystal of silicon whilst Poly panels use wafers that have been made from multiple crystals.  The manufacturing process for a single crystal is more complex than for Poly crystals which generally means that Mono panels are slightly more expensive than Poly panels.

The big question of course is “which is best”?

Mono panels are slightly more efficient than Poly panels but this should not lead you to the wrong conclusion.  A Poly panel rated at 230w has exactly the same output as a Mono panel rated at 230W!  The only real difference is that the Mono panel might be a bit smaller because it needs less surface area to generate that 230w.  The” Photon International” magazine’s outdoor test results published in May 2010 showed the top 5 producing panels in their test were all Poly.

In reality, the majority of panels on the market today are all capable of producing very similar outputs. Of far more importance is the overall manufacturing quality of a product that has to perform well on your roof for what might be a period in excess of 30 years.

Warranties and guarantees

Every panel manufacturer will offer both a warranty against faults in workmanship (typically 5 years) as well as a guarantee of output over a period of time. Typically they will guarantee that a panel will be performing at 90% of its original capacity after 10-12 years and 85% after 25 years. It is important not to confuse a “25 year output guarantee” with a general warranty of the product as they are simply not the same thing.  If somebody offers you a “25 year warranty/guarantee” you should look very closely at the details; it won’t be a guarantee to replace a non-working panel.

If you are offered a warranty/guarantee, you need to consider exactly what might happen in, let’s say, 10 year’s time when you feel that one of your panels might not be working properly.  There are currently a number of companies offering a 10 year insurance backed warranty on some Chinese panels. The insurance document is from a Chinese accident insurance company and would be completely worthless if you tried to claim against it. You would, at your own expense, have to get the panel disconnected from the array, arrange for it to be sent to a registered test centre, pay for the testing to prove it was faulty and then arrange for the faulty panel to be swapped for a working panel. You would then have to pay for the working panel to be re-connected to the array. Not much use to anybody.

The best form of guarantee is to work with a well-established installation company that cares about its reputation and is likely to be around in 10 year’s time.