Selecting a quality solar panel from the hundreds of different models and manufacturers can be a very difficult task. Here we provide a guide to choosing the best panels based on quality, efficiency, reliability, performance and return on investment. We also offer insight into the many innovations being used to improve panel efficiency and performance in our detailed solar technology review.
For those not familiar with solar, read our introduction to solar panels here. In summary solar photovoltaic (PV) modules or simply solar panels have not changed much in basic function over the last 30-40 years. Virtually all solar panels still use a series of silicon cells to convert sunlight to DC electricity. What has changed dramatically is the efficiency of the cells and more so the huge cost reduction to manufacture panels, which has come down by over 80% since 2008.
In Australia the Clean Energy Council (CEC) has an approved database of solar panels which ensure that certified solar installers use modules which are fire rated and conform to the solar & electrical safety standards. See the CEC approved list of solar modules here
How to choose a quality Solar panel
Unlike solar inverters the biggest problem when comparing solar panels is they generally look very similar with nothing obvious to distinguish between high and low quality products. Unfortunately many solar installers and customers only have the glossy brochure to go by, which can easily baffle people with clever marketing and slogans.
The common 'Tier 1' rating is also misleading and does not guarantee and panel is free from defects or will perform over the life of the system. The Tier rating was developed by Bloomberg New Energy Finance Corporation to rate solar panel manufacturers in terms of financial stability, it does not mean a panel offers the highest performance or quality. This is why a manufacturers reputation and history are just as important as their perceived quality. SunPower and LG energy are two manufacturers widely known as producing some of the highest quality solar modules with lowest degradation over time and best warranty conditions, however these panels also come at a premium price.
In addition to the Tier 1 rating it is important to select a quality and reliable panel based on company reputation, warranty details, test results and manufacturers service.
Determining a quality panel is made difficult as it is not something which can be pulled apart and checked; panels can only be assessed using specialised equipment which highlight small faults or hot spots, but this can change once the panels are installed outside in the weather for a few years. The sun’s UV radiation and high summer temperatures create extreme conditions for any roof top mounted solar panel and it can take 5 years or longer before any potential quality issues become apparent. This is why the manufacturer’s warranty period, service history and reputation are essential to selecting a quality solar panel.
Solar PV technology is constantly evolving and many new panel technologies have only been on the market for a few years. Solar panels ‘should’ have a lifespan of 25+ years so it is vital to use a manufacturer which has both a solid reputation and likely to still be in operation in the future to backup any warranty issues.
The standard warranty period for solar panels sold in Australia and most of the world is a 10 year product warranty, also known as a manufacturers warranty, and 25 year performance warranty.
1. Product Warranty
The product warranty is the manufacturers warranty which protects the customer against defects which occur from both manufacturing issues plus component or material failures. This means the manufacturer must either replace or provide a refund for solar panels which fail within the product warranty period. In general solar PV manufacturers must provide the minimum 10 year product warranty but a growing number of premium manufacturers (highlighted below) offer 12, 15 or even 25 year product warranties.
2. Performance Warranty
The performance warranty also referred to as the 'power output warranty' ensures that the solar panel still produces a minimum power output after a specific amount of time.
Once installed outside and exposed to sunlight, UV radiation and weather all solar panels slowly reduce output power over time (usually less than 0.8% per year).
The common industry standard is 80-83% power output retained after 25 years however some high-end manufacturers such as Sunpower and LG guarantee 86-92% power output on most modules after 25 years of use. There is also a growing number of manufacturers now offering 30 year warranties on the unique dual glass and bifacial solar modules.
Comparison chart solar panel product and performance warranties
Leading Solar Panel Manufacturers
Here is our short list of the best quality and most reliable panel manufacturers supplying the Australian market based on company history, quality, real world performance and feedback from solar industry professionals. See full details and description of the most popular high quality modules from the leading manufacturers using the links below.
Higher price equals higher Quality
Like most things, premium equipment also comes at a premium price. SunPower are considered the world leader but generally cost around 30% more than the competition. LG panels also come at a premium price but are more competitive on price and have a range of modules which are very well regarded and widely available which put them at the top of the list when it comes to both quality and value for money.
Why pay more? The additional cost for premium quality panels is typically $1000 - $1400 on a regular 5kW system. This is not a lot extra for panels which will no doubt outperform and outlast cheaper panels by many years.
When considering Return On Investment (ROI) it is necessary to take into account performance and degradation rates over the life of the system. Lower cost solar panels will mean lower upfront costs and may perform well for many years but over time (usually 4-6 years) most high quality panels will still be operating closer to the maximum power rating which means higher energy yields and greater returns. After 20+ years the higher quality panels will no doubt be out performing low quality panels by 10% or more which is a considerable amount when you calculate this over the annual generation.
DNV GL - Independent Panel Testing
One of the world’s leading independent solar module testing and performance services DNV GL produce the annual 'PV Module Reliability Scorecard Report'. The 2018 PV module scorecard recently released in May 2018 consists of four durability tests explained below. Over the last few years most of the top rated solar panel manufacturers have consistently scored as a ‘Top performer’ among many of the world’s leading solar brands tested. A top performer does not mean they are ranked as number 1 but among the highest performing module’s in the group with no severe degradation or failures.
DNV GL is one of the world’s most reputable, independent solar PV testing companies and so can provide a high level or confidence to the long term performance and reliability of solar modules for both large and small scale installations.
The scorecard rating is based on the four rigorous durability tests listed below which put panels through extreme temperature, humidity and loading to simulate the most severe real world conditions.
Thermal cycling test - Measures the module durability in extreme temperatures resulting in expansion and contraction.
Damp heat test - Measures module durability in high temperature and humidity and examines for signs of moisture ingress or corrosion.
Dynamic mechanical load test - This involves cyclic loading in extreme conditions causing module bending to simulate high wind and snow loads.
PID or Potential induced degradation test - measures current leakage or loss of power under high voltage, temperature and humidity conditions.
For more detailed information or solar module test results from numerous panel manufacturers it is recommended to refer to the annual PV Module Reliability Scorecard Report.
View the 2018 PV Module Reliability Scorecard Report here
LeTID - A potential problem
All solar panels suffer a small amount of power loss or degradation over time which is why the performance warranty allows for a specific amount of loss over a panels lifetime of 25 to 30 years. PERC cell technology increases panel efficiency and has been adopted by many of the world’s leading solar panel manufacturers, however it has only recently become apparent that P-type PERC cells can suffer what is known as LeTID or light and elevated temperature induced degradation.
The LeTID phenomenon is similar to the well known LID or light induced degradation where a panel will lose 2-3% of the rated output in the first year of UV exposure and 0.5% to 0.8% per year afterwards, although the losses due to LeTID have been found to be as high as 10% in the first 2 years and is not fully accounted for by all manufacturers which could lead to very poor performance and potential warranty claims.
Fortunately N-type silicon cells from LG, Sunpower and the new N-peak series from REC do not suffer the effects of LeTID. Also several manufacturers who use P-type poly and mono PERC have developed processes during manufacture to reduce or eliminate any LeTID losses, this includes Q cells who are the first to claim anti-LeTID technology on all panels. REC also claim to have reduced or accounted for the effect of LeTID along with Winaico and Canadian Solar.
Solar panels made in China
China is now considered one of the world leaders in crystalline silicon wafer and solar module manufacturing despite a poor reputation in the past. There are many reliable well established Chinese companies such as JA solar, Jinko Solar and Trina Solar which are constantly improving manufacturing quality, panel performance and spending big in research and development. Although there are still many lower quality panels coming out of China so always ensure a company has a good track record before purchasing any unfamiliar brand.
Several leading solar module manufacturers with the majority based in China have formed the Silicon Module Super League (SMSL) including:
Hanwha Q cells
Together these companies manufacture around half the the worlds solar modules and hold many of the most recent records for the most efficient mono and poly crystalline cells.
Many big name solar manufacturers from Europe and the US have also moved manufacturing to places like China, Malaysia and the Philippines over the years and as much of the process is actually automated the quality of products is extremely high, so long as you know which brands to choose. Q cells, JA solar and Trina Solar are well regarded by many Australian installers.
LONGi Solar has recently emerged as the largest supplier of mono-crystalline silicon cells in the world and along with Jinko Solar is leading the push towards the next generation of high efficiency low cost mono PERC panels.
Solar Panel Efficiency
The efficiency of a solar panel is a measure of the amount of solar irradiation or solar energy which falls on an specific area and is converted into electricity. In real world use the efficiency is also dependent on a number of different factors such as panel orientation, shading, dirt and cell temperature. A standard size (60 cell) panel with 16-18% efficiency typically has a power rating of 270-290 Watts where as a panel with higher efficiency of the same size can produce up to 340W using advanced cell technologies such as PERC and multi busbars. The most efficient panels explained in detail below use extremely efficient IBC or Interdigitated Back Contact cells which can achieve up to 21.5% efficiency and generate an impressive 370 Watts.
In terms of roof area the amount of roof space required is much lower for higher efficiency panels - For example 12 x high efficiency 360W solar panels such as those from LG or Sunpower with a 21% conversion efficiency can generate up to 1.2kW more power than the same number of lower efficiency 260W panels.
Efficiency of the various silicon solar cells*
Polycrystalline - 15 to 18%
Monocrystalline - 16 to 19%
Polycrystalline PERC - 17 to 20%
Monocrystalline PERC - 18 to 20%
Monocrystalline N-type - 19 to 21%
Monocrystalline N-type IBC - 20 to 22%
The term efficiency is thrown around a lot but a slightly more efficient panel does not always equate to a better quality panel. Many people consider efficiency to be the most important criteria when selecting a solar panel but what matters more is the quality as explained earlier. Quality is related to real world performance, reliability, company history and manufacturers warranty conditions.
The Most efficient solar panels
The highest efficiency solar panels widely available anywhere in the world in 2018 are the premium N-type IBC models manufactured by SunPower and LG Energy.
SunPower X series - up to 21.5% efficiency
LG energy Neon R - up to 21.4% efficiency
SunPower E series - up to 20.4% efficiency
See full details in the solar panel technology review here.
All manufacturers produce a range of panels with different efficiency ratings depending on the silicon type used and whether they incorporate PERC or other cell technologies. Very efficient panels above 20% are generally much more expensive, so if cost is a major limitation it would be better suited to locations with limited mounting space , otherwise you can pay a premium for the same power capacity which could be achieved by using 1 or 2 additional panels. However high efficiency panels using N-type cells are also generally very high quality and more often than not they outperform and outlast lower efficiency panels due to lower degradation rates, so the extra cost is usually well worth it.
Example a high efficiency 60 cell 330W panel could cost around $300-320 while more common 285W panels typically cost closer to $170-$180. With both made by the same manufacturer, this equates to roughly $0.60 per Watt compared to $0.90 per Watt. Although in the case of LG, Sunpower and Winaico, the more expensive panels have higher performance, lower degradation rates and generally come with a longer 'manufacturers' warranty period, so it is often a very wise investment.
Well known manufacturers including Trina Solar are working on the next generation high efficiency IBC cells, this direction is also highlighted in the development roadmaps for a number of other Chinese manufacturers.
Panel Size Vs Efficiency
Panel size is not always related to efficiency as larger size panels generally just incorporate more cells (ie. 72 cells per panel) to achieve greater power output. The two most common panel sizes are below: (rounded to nearest cm). Most residential installation use 60 cells panels* while commercial and large scale solar farms use larger 72 cell panels*.
Medium : width 1.0m x length 1.65m (typical 60 cell)
Large : width 1.0m x length 2.0m (typical 72 cell)
The new generation half-cut or split cell modules have double the amount of cells at roughly the same size and capacity, so a panel with 60 cells is now doubled to 120 and 72 is now 144 cells. The half size cell configuration is efficient but the panel voltage is still roughly the same as the to halves are combined in parallel.
Latest PV cell technology review
Learn more about the leading solar panel models and cell types here including PERC, multi busbar, split modules and bifacial panel technology here.