high efficiency, Sunpower, quality, LG, Panasonic, X22, X21, X20

What is the Most Efficient Solar Panel?

At Joju Solar, one of the most common questions we are asked is “what is the most efficient solar panel?”  Here’s our guide to the best of the best.

More efficient photovoltaic systems produce more electricity from every square meter of roof space, so they are an attractive means of using space in the most efficient manner possible. However, they do come at a cost penalty compared to conventional modules, as you might expect from a high-end product. It is therefore important to understand what types of solar installation should use this class of modules.

When should I use high efficiency modules

There are several key reasons to use high efficiency modules:

  • Where you want to generate as much electricity as possible.  For those with an electric car, any additional generation equals more zero-carbon miles of transport.  If switching to higher efficiency modules could give you an extra 1kWp of capacity, that could equate to 3000 miles of free travel.
  • Where space is limited.  For small roofs, we always recommend using high efficiency modules.  This is because every solar installation contains a certain amount of ‘fixed costs’ such as scaffolding and labour which have to be paid anyway, and for small rooftops these are disproportionately high.  It is better therefore to install as much solar capacity as possible once you are up on the roof.  This is particularly true for solar panel installations in London and other urban centres where roof sizes are smaller.
  • Where quality is important. High efficiency photovoltaic panels are the pinnacle of solar technology.  If you want the best of the best, then high efficiency modules are the obvious choice.
  • Where you want to minimise risk. The performance of high efficiency modules tend to be backed with very long warranties.  Whilst high efficiency modules may not be the obvious choice for a commercial solar project (as they are more costly, and not space limited), they may be an appropriate choice if the client is particularly concerned about risks associated with investment. For this reason, we do often see high efficiency modules specified in commercial project tenders.
  • Where aesthetics are important – due to the way they are made, high efficiency panels tend to have look sleeker and have cleaner lines than conventional modules. They can also come with a range of black frames and black backing material (all-black modules).  This can be helpful if trying to integrate with a slate roof, or if you are in conservation areas or listed buildings where planning issues are sensitive.  This church used high efficiency solar panels to help with the planning process.
  • There are other niche applications too! If you’re trying to fly a plane with solar power, you need as high an efficiency cell as possible, with minimal weight.  It’s no coincidence that the Solar Impulse 2 zero fuel airplane uses high efficiency SunPower cells on its wings.

Sunpower, X21, high efficiency, solar panel

Sunpower’s high efficiency cells are available as sleek modules, or as an elegant all-black module for seamless roof integration.


What are the most efficient solar panels?

Here’s our rundown of the top 10 highest efficiency solar panels.  SunPower dominate the top spots but LG and Panasonic come second and third respectively.  Remember, a conventional solar panel is typically 16-16.5% efficient, so you can see the boost in production from the numbers below.

  • SunPower Maxeon3 400W Panel In 2019 the SunPower launched their 400W panel; the most efficient commercially available solar panel in the world at 22.6% panel efficiency. There’s nothing else around that can offer such high efficiency.  This is also available as a slightly lower powered 390W version.
  • LG Neon R 370W Panel LG’s newly released solar panel is snapping at the heels of Sunpower at 21.4%. Its physically larger than the Sunpower modules which will explain the higher peak capacity.
  • SunPower Maxeon3 375W All Black Panel This is by far the most efficient all-black solar panel available at 21.2% to combine high efficiencies and superior aesthetics.  Its our go-to product where looks and efficiency are important
  • SunPower Maxeon2 360W Panel Slightly cheaper than the Maxeon 3 technology, this is probably the most popular residential solar panel in Sunpower’s range at 20.4%.
  • SunPower E20 435W Com A large, two-meter-long panel made for the commercial market with industry leading warranties, efficiencies and a more competitive price point. (20.3% efficient). The learger size allows for quick installation and a minimum of mounting support.
  • SunPower E19 315W All Black The P19 315W All black panel at 19.9% efficiency combines the attractive All Black finish with a more modest price point.  This product is ideal for projects where both the amount of generation and returns on investment are important.
  • Panasonic N 330W Panel Until SunPower arrived in the UK Panasonic (formerly Sanyo)  held the top spot in terms of panel efficiency for many years. Panasonic are still in third place with this 19.7% module.
  • LG Neon 335W Panel LG combine efficiency and value in this 335W solar panel at 19.6%.

(Correct as of 11/7/19)

How do they make high-efficiency panels?

SunPower, LG, and Panasonic have all made technical innovations that improve the efficiency of their cells compared to conventional modules

  • SunPower have made an all-back-contact cell, which mean that both the +ve and –ve electrical connections are on the rear of the cell. That means no collector wires on the front surface, which increases the area available for collecting the sun’s energy.  We also think it makes them look super neat, with a more uniform look to their front surface.
  • LG have also made an all-back-contact cell, eliminating collecting busbars on the front of the module.
  • Panasonic have adopted a different approach, called an HIT cell. They use two layers of different materials to make each cell, called crystalline silicon and amorphous silicon.  Crystalline silicon is great at absorbing red light, and amorphous silicon is great at absorbing blue light.  Put the two together and you can capture a wider range of colours than a conventional cell, which improves efficiency.

What do Joju Solar offer?

At Joju, we’re technology agnostic, so we’re happy to specify any solar panel you wish.  However, we are big fans of SunPower – their dominance of the above table is a clear demonstration of their quality.  We’ve been official Sunpower partners ever since they became available in the UK in 2011.

Another reason we like SunPower is due to their industry leading warranties. SunPower panels have a 25-year performance and product warranty. Not only will they replace a panel if it is under performing, they will cover the cost of access like scaffolding and labour. With conventional modules only coming with 10 year warranties, and guaranteeing lower levels of performance, no other manufacturer comes close to offering the same security. You can see why SunPower are comfortable offering this – they are particularly robust and have a low failure rate. In fact, we have never had any performance issues with our SunPower modules.

As well as having the highest rated efficiencies, SunPower panels do very well in the real world. We have over 5 years of generation data from our SunPower installations so we can assess how they perform. Our Head of Engineering James Page has published the results of his study and found that as well as doing what they say on the tin, SunPower panels perform particularly well at low light levels. This means they perform well across the year, even in winter when the solar resource is lower.

Lastly, and it might seem like a minor point to some, but SunPower panels look really good. They have attractive black frames and the lack of wires on the front of their cells to give the panels a uniform and sleek appearance.

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