Solar panel:  efficiency and photovoltaic cells

Solar panel: efficiency and photovoltaic cells

John, DIYer & IT developer, Brighton

Guide written by:

John, DIYer & IT developer, Brighton

71 guides

Photovoltaic panels recover energy from the sun and transforms it into electricity. When it comes to accurately defining the ability to do so, we refer to a solar panel's performance. In practice, it depends on photovoltaic cells themselves, as well as their surface area and their orientation and the amount of sunshine they receive.

Important features

  • Cell type
  • Orientation
  • Angle
  • Surface in m²
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What is a solar panel's performance?


A solar panel's conversion efficiency is calculated by dividing its maximum electrical power output (expressed in watt-peak or Wcby the power of the solar radiation that is absorbed.

Expressed as a percentage (%), this value represents the fraction of solar energy that is successfully converted into electrical energy. The higher this value is, the more efficient the solar panels will be. 
If you have the choice between type-A panels or higher-efficiency type-B panels of equal area, the latter will produce more electricity. Working with the same amount of power, it will take a larger type-A panel to produce the same amount of energy.

If space is an issue, either because your home's roof is small or if it used to power very hungry devices on your camper, it's best to go with high efficiency panels, even if they are more expensive. 
On the other hand, if your installation doesn't require too much power, and space is widely available, lower efficiencyphotovoltaic panels, which are therefore less expensive, are ideally suited.

Photovoltaic panels performance


There are currently a whole host of differnt technologies that make use of photovoltaic cells, some of which can obtain a performance level that exceeds 60%. Unfortunately, most of these technologies have been developed for very specific uses such as space travel, and do not have any mainstream application at the moment, mostly due to their price tag.

The photovoltaic cells that are available on the consumer market are composed of silicon. The different models will offer varied yields, depending on how the silicon crystal is made. There are 3 types of silicon-based cells, which will generally have a yield of anywhere up to 25%.

Amorphous silicon 

These cells can produce up to 60 Wc/m², which adds up to a yield of around 6%, at it's peak in the sun. Relatively inexpensive to make, these are the types of panels that are often found of small electrical devices such as watches or calculators. They can be adapted to fit a wide variety of supports, making for surprising uses.

Monocrystalline silicon 

This type of cell can produce up to 150 Wc/m², ora yield of 16 to 24%. They are made of a single silicon crystal that is cut into thin slices which gives off a distinctive blue shade. The process needed to manufacture them results in a hefty price tag, and the overall yield they can produce will drop during a bout of low exposure or with diffused light.

Polycrystalline silicon 

This type of cell has a yield of about 15% and can produce 100 Wc/m². It is fashioned during the cooling of the molten silicon, where several crystals are formed, giving the cells a bluish shade. Their performance is negatively impacted by low light conditions and diffused light.

What other parameters can affect a solar panel's performance?


Properly installing your solar panels is essential. Their yield is heavily dependent on their orientation and angle, wielding up to 30%.

Your new, expensive solar panel may boast a high performance on paper, however it will not live up to this expectation if improperly installed. A solar panel should  ideally be orientated due south, to reach its peak production when the sun is at its highest.

A solar panel that is pointed south-east or south-west will have a 4-5% loss. Point it towards the east or the west and this loss could increase up to 20%.

Ideally, a solar panel should be tilted at 30-35°horizontallyA perfectly flat panel will yield a 10% decreased performance, while placing them vertically will result is a 30% loss.  
It's important to take care in choosing the right spot to install your photovoltaic panels, to allow them to live up to their full potential! Finally, of course, never forget to clean their surface of the panels from time to time.

More information

Installing solar panels is a big project that requires a lot of knowledge. To make sure you have everything you need, follow the links below for related accessories, advice from our editors and more helpful guides:

And to make sure you have all the right tools:

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Guide written by:

John, DIYer & IT developer, Brighton, 71 guides

John, DIYer & IT developer, Brighton

Since I was a child, I was always interested in manual and technical works. Always fascinated by woodworking, I took advantage of my first flat as a playground. On the cards: electricity (of course, safety first!) and some partition walls; but also decorating with the help of the missus, made-to-measure furniture and little tricks to optimise the space, all the while remaining as original as possible. When the little one arrived, I started building bits and pieces for him! Lacking space, I have not got a permanent workshop and certain tools I dream about but are not part of my collection. Not to worry, I already know a lot about DIY and I have a high-tech profile that I hope will guide you in your decisions!

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