Solar PV Knowledge Bank

High Efficiency Solar Panels: BenQ and SunPower PV Panels

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Introduction

SunPower: The best high performance solar panels on the market: 50% increase in lifetime generation from the same roof space, the BEST warranty on the market.

BenQ: Similar panel (efficiency, technology), lower price, lower warranty commitment than SunPower.

If you've done even the slightest bit of research on solar panels, the chances are you've come across the name SunPower. Founded and based in Silicon Valley, SunPower has come to dominate the residential solar industry with their premium high efficiency panel offering. But what makes the SunPower brand so special, if indeed it is?  And what about BenQ solar panels?

SunPower: relentless innovation, backed by Total

The principal factor behind SunPower's success is their leading solar cell technology. SunPower produces a range of high efficiency solar panels with efficiencies of over 20% thanks to their patented back-contact cell design which maximises usable collection area (see below). On top of market-leading efficiency, SunPower also offers the best warranty on the market, both in terms of defects and performance. Finally, SunPower is backed by Total, the world's 10th largest public energy company.  

SunPower: cell technology

SunPower has spent over US$450million on R&D in the last 10 years; it is thus unsurprising that the company holds more than 750 patents.  The underlying technology that gives rise to SunPower's superior panel performance is their patented MaxeonTM solar cell. 

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These solar cells differ from conventional cells in that they utilise back-contact technology, which means no current collecting wires ('fingers' and 'busbars') on the top surface of the cells. MaxeonTM cells instead employ solid copper backing sheets to provide both the positive and negative electrical connections at the rear of the cell. As a result, the top surface area is maximised for better absorption of  sunlight. 
 

The copper foundation also offers durability advantages over the porous metal paste used for front and back contacts in conventional cells. MaxeonTM cells are less susceptible to cracking and corrosion - the two main causes of cell degradation. 

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Superior performance: 30% higher efficiency, 20% higher lifetime output

The higher solar cell efficiency of SunPower equates to more output per square metre. So for example, the top performing X-Series 360W panel has a peak output of 360W out of an area of 1.63m2 - that's 221W per square metre.  'Standard' panels typically generate 150W - 170W per square metre. So SunPower enables you to install a 30% bigger system in a given roof space.

In addition, the output from SunPower solar panels degrades at a much lower rate (around 0.20% per annum instead of the standard 0.75% degradation). Furthermore the panels exhibit superior performance in hot rooftop conditions, and in partial shade.  Overall SunPower claims that a SunPower panel will produce around 20% more energy over the life than a similar rated standard panel.  

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The following graphic is available in the SunPower datasheets which you can download above.  The 'output premium' increases from 9% in year 1, to 36% in year 25, the average being around 21%.  The claim is supported by yield and degradation test reports.

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SunPower: clean aesthetics, black available

SunPower panels also look good. Choose from their signature dark blue panel or the sleek black panel shown above.

How does BenQ compare?

BenQ's SunForte PM096BW0 327W panel is very similar in performance to SunPower's E Series 327W panel. The BenQ product also uses back contact cells (although it does not claim to use exactly the same cell technology as SunPower), and also exhibits superior performance at high temperatures. Both panels have an efficiency of 20.4%.

The key differences lie in cost and in warranties:

  • BenQ is approximately £200 less expensive than SunPower per kWp (so £800 less than SunPower for a 4kWp system);
  • SunPower offers a superior warranty, as discussed below.

Further, BenQ does not offer the same sleek black option that SunPower offers. However the panels still look good, owing to the lack of lines running across the cells. Here's a photo of an installation we recently completed in London using BenQ solar panels:

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Finally, BenQ does not list as many of the quality features that SunPower lists.

SunPower includes the following as standard in the build of its modules, improving reliability and thus facilitating the superior warranty:

  • the SunPower panel frames use adhesives from the aerospace industry to connect to the solar laminates, and are thus designed to withstand cyclonic wind loads;
  • the cells use high grade n-type monocrystalline with minimal impurities;
  • exceptional resistance to moisture and electrical stresses provides superior reliability;
  • tin corrosion barrier: the copper foundation is plated with tin to make it nearly impervious to corrosion;
  • the SunPower panels use triple redundant cell interconnections use built-in strain relief, thus allowing for expansion and contraction from daily temperature swings;
  • anti-reflective glass with high levels of quality control ensures a uniform glass layer maximising production on cloudy days.

Superior warranty

The industry standard for solar panels is a 10-year product warranty covering manufacturing defects, along with a performance guarantee that the panels will generate at least 80% of their initial output to 25 years. There is inevitably conflict over the boundary between these two warranties: the 25 year output potentially depends on the panels not having any manufacturing defects - thus there is a lack of clarity in the value of the standard power warranty alone beyond the 10 year coverage of the product warranty. Further there is no service warranty, covering the removal, installation and transportation costs of a failed panel. 

SunPower 

SunPower, extends the defects cover over 25 years and guarantees that their panels will output 92% of their original output at the 25-year mark, rather than the 80% of the standard panel. This implies a 7% lifetime output advantage over a standard panel per watt, however SunPower actually claims that their panels can produce over 20% more energy per rated Watt over 25 years.

Furthermore, in the seemingly improbable event that one of their panels does develop a fault at any point over the 25 years...SunPower will cover the complete cost of removal, replacement or repair, AND re-installation, as well as transportation costs for the return of defective panels and shipment costs for repaired or replaced panels! 

This supreme confidence in the quality of their products distinguishes SunPower above all other manufacturers operating in the PV industry.  

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BenQ

BenQ's product warranty is much better than a standard panel warranty, but not as good as the SunPower warranty.

Specifically, BenQ gives the same 25 year warranty for material and workmanship that SunPower gives, but the BenQ warranty doesn't cover the costs of transportation, removal and re-installation.

Further, on the output guarantee, BenQ warrants 95% of rated output for 5 years, with linear degradation to 87% to the 25 year mark. SunPower offers a similar warranty in the first 5 years (see graphic above "SunPower Customer Advantage"), but guarantees less degradation to a superior level of output (92%) at the 25 year mark.

Premium products, premium price...

SunPower panels really do represent the best quality technology on the market, but unsurprisingly this comes at a price. 

There are three ranges of panels to choose from: the X22, X21 and E20 series in descending order of panel efficiency. The E20 327 Wp panel is the standard offering for domestic installations as it offers the most competitive value for money, costing just over 50% more than the best value high efficiency monocrystalline panels on the market. Since the panel cost will typically constitute around a third of the total installation cost for a 4 kWp domestic system, by choosing to go with SunPower panels you can expect to pay ~20 to 25% more for your system.   

SunPower solar panels cost 15% more

With BenQ solar panels the system cost will typically work out at a 12% premium to a standard system cost.

So should you go for it?

If you can afford the additional upfront cost, we absolutely recommend you go for either BenQ or for SunPower panels. If roof space is a limiting factor, as it often is, you will win on two counts versus a standard panel:

  • SunPower and BenQ will enable you to get more out of your roof space, increasing the rated system output by 30%;
  • the SunPower system will exhibit superior lifetime performance, generating approximately 20% more power over the lifetime than a similarly rated standard system. BenQ also guarantees a better overall performance (by about 3%) than a standard system.

Overall you can get 50% more power out of the same roof space with SunPower! You will also benefit from the superior warranty cover, and you'll be making a top aesthetic choice, whether you go with the classic dark blue or opt for the elegant all-black module for the ultimate visual statement. If you feel the SunPower is too expensive, however, BenQ is a definite second best.