Solar panel buying tips
Spend more money on inverters since solar panels are very reliable.
Manufacturer experience
The time a company has been in business is important, since it brings cumulative knowledge and experience. However, companies such as Tongwei have entered the market and quickly become the largest solar company in the world. Sometimes new companies have access to the very latest manufacturing plant, increasing the quality control and the latest techniques of panel production.
Most solar companies comply with ISO 9001 to ensure management excellence in continually monitoring, managing and improving the quality of their products.
Origin of panels
Solar panels do not fail very often. Many of the top panels are now manufactured in Asia. Some Chinese companies, such as JA Solar, have more experience in manufacturing than some German companies such as Axitec and Solar-Fabrik. 80% of the panels in Europe are now manufactured in China. The only company we are aware of assembling solar panels in the UK is GB-Sol.
From 3.5 million panels manufactured and sold in Europe, only 137 panels have failed (0.00381%).
| Manufacturer | Experience (years) |
|---|---|
| Panasonic (Sanyo) | 49 |
| LG | 39 |
| Hanwha Q.Cells | 26 |
| Canadian Solar | 24 |
| JA Solar | 19 |
| Manufacturer | Company | Origin |
|---|---|---|
| BenQ | Taiwan | Mexico/China |
| Canadian Solar | Canada | China |
| LG | South Korea | South Korea |
| Panasonic | Japan | Singapore |
| Jinko | China | China |
Panel efficiency
Efficiency is about the size of the panel vs its output in lab conditions.
Example
System 1: 16 x JA Solar 250w panels = 4kW system.
System 2: 10 x Panasonic 400w panels = 4kW system.
Both systems should produce the same amount of energy.
The main difference is the Panasonic system will take up less roof space, since it is a more efficient panel.
Panel efficiency is only important if you have a smaller roof space, which is not large enough for your desired system size.
There are only three reasons to buy high efficiency panels:
Panel performance
Performance is about how the panels will actually perform on your roof.
Example
System 1: 16 x JA Solar 250w panels = 4kW system.
System 2: 12 x Panasonic 330w panels = 4kW system.
According to lab tests, both systems should produce the same amount of energy.
However, in real life conditions the performance tends to vary quite a bit – up to 18%.
The only way to know which panels will perform better is by looking at independent field tests where panels are installed alongside each other in real life situations.
Panel aesthetics
Frame colour
If you have a dark roof such as slate, we recommend black frames for aesthetic reasons.
Cell colour
There are two main types of cells:
Backsheet colour
If you have a dark roof such as slate, we recommend black rather than white backsheets. Black backsheets do increase the temperature of panels and slightly reduce the efficiency of the panel.
In the past, monocrystalline were more efficient than and considered superior to polycrystalline panels. This has now changed with some polycrystalline panels being more efficient than monocrystalline. Some panel companies may have better performing polycrystalline panels, while others may have better performing monocrystalline panels.
Back Contact and Shingled Solar Panels
Back contact solar panels even move the silver contacts running across the front of the solar panels to the rear of the panel. Shingled solar cells use electrically conductive adhesive on the back of the panel to form a contact.
Warranties
Product warranty
When comparing panels, the product warranty is important, since if the reason for failure meets the warranty conditions, it will be replaced. A 10 year warranty from a well-known financially stable manufacturer is probably worth more than a 12 year warranty from an unknown manufacturer.
In the 9 years we have been installing We have only had one panel where we have needed to make a warranty claim.
Performance warranty
Every panel sold in the UK needs to have a 25 year performance warranty – this means the panel will lose less than 20% of its output over 25 years.
It is extremely unlikely that anyone will ever claim under performance warranty, since the costs involved in proving the panel has failed will be more than the panel replacement cost.
For this reason, performance warranty is less important when comparing panels.
Degradation
Panel performance does deteriorate over time (known as degradation or panel induced degradation – PID). Some panels are appearing that are “PID free” such as some panels from LG and BenQ.
