SunPower Solar Panels

Introduction

SunPower panels are the best high performance solar panels on the market, with the manufacturer claiming on their website that their Maxeon 3 panel offers up to 30% increase in 25 year generation than other panels.

13% of this claim is easy to attribute:

• their improved efficiency means they can get 9% more than other panels from the same roof space; and
• their low annual panel degradation further increases output relative to other panels by 4% over 25 years. 
  
  The remaining 17% of their claim is harder to attribute - it comes down to factors such as operating temperature etc (see below).

Further, in 2022, to set themselves apart from the market, Sunpower increased the 'headline' warranty of their panels to 40 years! An increase of 15 years over and above the market standard. But when you read the fine print, it's a fairly limited 40 year warranty (see below), so check the fine print if you find the 40 year warranty swaying your buying decision.

Unfortunately, Sunpower panels are significantly more expensive than other panels, and, overall, unless you are trying to squeeze the last bit of generation from limited space, this additional cost can be hard to justify. You could counter the 9% increased output per square metre from Sunpower panels by covering 9% more roof space with panels.... unless you don't have that 9% more roof space.

SunPower: relentless innovation

If you've done even the slightest bit of research on solar panels, the chances are you've come across the name SunPower. Founded in Silicon Valley, SunPower came to dominate the residential solar industry with its premium high efficiency panel offering. In 2020, Maxeon Solar Technologies was spun off from US-based SunPower Corporation as an independent company that sells SunPower panels internationally. But what makes the SunPower brand so special, if indeed it is?

The principal factor behind SunPower's success is its leading solar cell technology. SunPower solar cell efficiency is the best on the market.

Maxeon produces a range of high efficiency solar panels with efficiencies of up to 22.7% thanks to their patented back-contact cell design which maximises usable collection area (see below). On top of market-leading efficiency, SunPower panels also come with the best warranty on the market, both in terms of defects and performance.

SunPower panel range

Maxeon effectively offers two ranges of panels: SunPower Maxeon and Performance.

SunPower Maxeon

Maxeon 3 - White	Maxeon 3 - Black

SunPower Maxeon is the absolute premium product, with the highest efficiency of any panel on the market. The commercial panels are a larger format to reach a higher output.

The all-black versions are slightly less efficient (because the darker colour increases module temperature), and so cover the lower output range.

Maxeon has also released an AC solar panel version, the SunPower Maxeon 5, which includes integrated micro-inverters.

SunPower Performance

Performance Residential	Performance Commercial

SunPower Performance is a slightly lower efficiency (and less expensive product), similar to other monocrystalline panels in cost and performance. They use monocrystalline PERC cells, rather than the back contact technology in Maxeon panels. Again there are two ranges, one for Residential and one for Commercial. The Residential and Commercial panels have similar efficiencies (similar output per square metre) but the Commercial panels are physically bigger, and hence output more per panel.

SunPower: cell technology

SunPower Corporation 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 its patented Maxeon solar cell.

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. Maxeon 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. Maxeon cells are less susceptible to cracking and corrosion - the two main causes of cell degradation. 

Superior performance: up to 30% higher lifetime output from the same space

The higher solar cell efficiency of SunPower equates to more output per square metre. So for example, the top performing Maxeon 3 430W panel has a peak output of 430W out of an area of 1.90m² - that's 227W per square metre. Standard monocrystalline panels typically generate 208W per square metre. So SunPower enables you to install a 9% bigger system in a given roof space.

In addition, the output from SunPower solar panels degrades at a much lower rate (around 0.25% per annum for Maxeon and 0.5% for Performance, instead of the standard 0.55% per annum degradation for say Trina or JA Solar panels).

Over the 25 year life, these two factors combined, mean that Sunpower will output 13% more than a standard panel:

Sunpower claims many other advantages, which they say can lead to an overall 30% output advantage, rather than 13%:

Firstly the panels exhibit superior performance in hot rooftop conditions, and in partial shade.

For example, the temperature coefficient (reduction in power output at cell operating temperatures above the ‘standard’ operating temperature – usually 45°C) is -0.27% for SunPower Maxeon panels, compared to -0.39% for a standard polycrystalline panel, and -0.34% for the SunPower Performance range. So with a 10°C increase in operating temperature, output will drop 2.7% with Maxeon and 3.9% with standard panels. These seemingly small differences add up over many years.

This ‘output premium’ is lower for other panels (see datasheets).

SunPower manufacturing

SunPower cells are manufactured in the Philippines. The modules are assembled in Mexico. The company is dedicated to making the most sustainable solar panels - the Maxeon 3 was the first to be Cradle-to-Cradle Certified.

Maxeon 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 to 15 year product warranty covering manufacturing defects, along with a performance guarantee that the panels will generate at least 85% of their initial output to 25 years. You can compare different warranties on this page.

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 10-15 year coverage of the product warranty. Further there is generally no full service warranty, covering the removal, installation and transportation costs of a failed panel. 

Maxeon claims to offer a superior warranty for a number of reasons, summarised in this table:

Maxeon extends the defects cover over 25 years and guarantees that its panels will output 92% of their original output at the 25-year mark, rather than the 85% of the standard panel. This implies a 4% lifetime output advantage over a standard panel per watt, however, as above Maxeon actually claims that their panels can produce over 30% more energy per rated Watt over 25 years.

For SunPower Maxeon panels, the warranty can be upgraded to a groundbreaking 40 years for product, performance and service by registering the installation. In this case, Maxeon guarantees 88.3% output after 40 years, on the face of it an incredible vote of confidence in the durability of these products.

But, as always, the devil is in the detail. You can download the 40 year warranty below. And if you read the fine print, it does say:

For any valid claim hereunder pertaining to any PV Module, Maxeon will, in its sole discretion, repair, replace, or refund the original purchase price of the covered PV Modules.   

This means, they can choose to refund the original purchase price. And then they further limit the amount they will refund as follows:

If Maxeon issues a refund under a valid Product or Power Warranty claim, then Maxeon will refund the original purchase price for the first five years of the applicable Warranty Term, and then linearly depreciate the refund amount by 2.78% per year for 40-year Warranty Terms, 13.5% per year for 12-year Warranty Terms, and 4.75% per year for 25-year and other Warranty Terms (the “Claim Value”), provided that for a valid Power Warranty claim, Maxeon will refund the Claim Value multiplied by the percentage difference between the Guaranteed Peak Power percentage and the Measured Peak Power percentage (both as a percentage of the Minimum Peak Power). 

For repairs and replacements, Maxeon will pay reasonable, customary transportation costs for the return of covered PV Modules from, and the shipment of repaired or replacement PV Modules to, the place where the covered PV Modules were originally delivered by Maxeon. They will contribute up to £225 to repair up to 5 modules, and then £45 per panel. This may not cover the scaffolding costs.

Premium products, premium price...

SunPower panels really do represent the best quality technology on the market, but unsurprisingly this comes at a price: around £480 per kWp (so just under £2000 for a 4kWp system).  That's about a 25% uplift, depending on the overall project complexity.

For this to be justified, you would want to see a 25% uplift in output. You will get 4% from the lower degradation, and, only if space is limited, you will get 9% more out of your limited roof space. But you may not see a 25% increase in output overall .... unless of course your panels last 40 years, and all alternative panels completely malfunction after 25 years (unlikely, since panels have been proven to last 30 years plus now).

So should you go for it?

If you can afford the additional upfront cost, on balance probably yes. If roof space is a limiting factor, as it often is, you will win on two counts versus a standard panel:

• SunPower will enable you to get more out of your roof space, increasing the rated system output by up to 13%;
• the SunPower system will exhibit superior lifetime performance, generating as much as 17% more power due to better real world performance than a similarly rated standard system.

You will also benefit from the superior warranty cover, and you'll be making a top aesthetic choice.

Product brochures

Discover the range of SunPower solar panels:

• SunPower Maxeon 3 White [415W – 430W]
• SunPower Maxeon 3 Black [410W – 420W]
• SunPower Performance Residential [370W – 390W]
• SunPower Performance Commercial [405W – 420W]
• SunPower Maxeon Warranty
• SunPower Performance Warranty
• 40 year panel Warranty