How to choose a solar panel
Written by Gavin Bulmer
So, you have decided to install solar panels to provide clean, renewable energy to your home or business. But how do you decide which solar panel to install? Each potential installer proposes a different brand, how are you to tell the difference between them?
In this guide we look at some of the key areas to consider when choosing a solar panel, after all this is a long-term investment so price is not always king.
Which type of solar cell?
There are currently two mainstream types of solar used when manufacturing solar panels, although they are broken down into three products and it is important to know a little about them before making your final decision.
Crystalline Silicon is the more common and is normally referred to as Monocrystalline or Polycrstalline.
Generally considered to be the premium product, Monocrystalline has better aesthetics and higher efficiencies. Monocrystalline solar cells are made from a single crystal of silicon. Because the cell is made from a single crystal the electrons have more freedom to move and therefore display higher efficiency than other silicon solar cells.
Typically a more affordable product, Polycrystalline silicon does tend to have lower efficiency. Polycrystalline solar cells are still made from silicon, but instead of a single crystal, manufacturers melt many fragments of silicon together to form the solar cells. Because the cell is made from many crystals there is less freedom for the electrons to move and therefore the panel displays lower efficiency.
Sometimes called “thin film”, Amorphous solar panels are manufactured by depositing a thin layer of photovoltaic material onto a carrier material, such as glass or plastic. Amorphous solar panels can be recognised by the purplish-black appearance of the panel without any solder or weld lines. Amorphous solar cells work better in lower light conditions but as they are less efficient than crystalline cells you will need a greater area to achieve the same power. Another drawback of thin film type solar is that it will degrade rapidly between 15%-20% in the first 90 days before levelling out. By comparison a crystalline solar cell will likely degrade by that amount across its entire 25 to 30 year lifespan.
Solar panels are normally rated in Watts peak (Wp). This is an important consideration when choosing which solar panel. You may hear your installer refer to a “285 Watt panel” or see numbers like 300Wp, 310Wp or 340Wp written in the proposal. They are all referring to how much power the solar panel can produce in Standard Test Conditions (STC).
Standard Test Conditions are the industry standard and allow us to compare products accurately.
There are three standard test conditions which are:
- Temperature of the cell – 25° This is the temperature of the cell and not the air surrounding it.
- Solar Irradiance – 1,000 Watts per square meter. This number relates to the amount of light energy falling onto a given area at a given time.
- Mass of Air – 1.5. This number is a little misleading as it refers to the amount of light that has to pass through the Earth’s atmosphere before it can hit the Earth’s surface.
The higher the Wattage of the panel you choose, the more electricity you will generate for your home or business. Generally, a higher wattage solar panel will cost more than a lower wattage panel, so consider how much space you have and how much power you need.
If you are trying to maximise the amount of energy that your solar system can generate, then you will need to be familiar with the temperature coefficient.
A solar panel’s temperature coefficient is the influence that a panels temperature has on its productivity.
Temperature coefficient is expressed as the percentage decrease in output for every 1°C increase in temperature from 25°C.
Most solar panels have a temperature coefficient of around -0.3% to -0.5% per °C. This means that for every 1°C the solar cell is above 25°C, the solar panel efficiency will fall by 0.3% to 0.5%.
This might seem like such a small amount, but when you consider that a solar cell can reach operating temperatures of 65°C, these increments can soon add up.
Solar panels are a long term investment and it is therefore crucial to ensure that your choice of panel has a reliable warranty.
There are often two types of warranties offered with solar panels; a product warranty and a performance warranty.
The solar panel product warranty covers any defects in materials or workmanship. If the solar panel stops working after just a few months because of a faulty junction box, for example, the product warranty will likely cover this. Product warranties range from five years to 30 years depending on the quality of the solar panel you choose. A product with a 30 year product warranty is likely to be reliable and perform well as the manufacturer has guaranteed it. The price will reflect this and these panels are often more than twice the cost of a lesser panel with a five year warranty.
The power performance warranty of a solar panel covers the output of the solar panel. Over time, the power output of a solar panel will reduce due to ageing of the solar cells. Knowing the rate at which this will happen allows you to compare how much energy you can expect to produce in the future for each panel. Some manufacturers will give a stepped warranty, guaranteeing the minimum panel output at set intervals, typically 2, 10 and 25 years. Other manufacturers will give a linear performance warranty, they will guarantee the maximum rate of degradation per year for the period of the warranty. This makes it relatively easy to work out which panels are high quality and which are lesser.
Let the solar experts help you choose
SaveMoneyCutCarbon have a team of qualified experts that can help you choose. We work with leading manufacturers of solar panels from around the world to ensure that we can provide the right product for your system at the right price for you.
Act Now and call the SaveMoneyCutCarbon solar PV team today to secure your energy future.
Call us to start your solar journey
0333 123 5464