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Detailed reviews and information of the best solar panels, inverters and batteries. Plus hybrid and off-grid solar system reviews and information articles on how solar and battery systems work.

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Reviews and information of the best Solar panels and inverters from SMA, Fronius, SunPower, SolaX, Q Cells, Trina, Jinko, Selectronic, Tesla Powerwall, ABB. Plus hybrid inverters, battery sizing, Lithium-ion and lead-acid batteries, off-grid and on-grid power systems.

SunPower Solar Panels Review

Jason Svarc

SunPower solar panel Review.jpg

Company background

SunPower Corporation has a long, rich history in solar manufacturing and many consider them to be the solar industry technology leader. This is a big claim but as we explain they currently produce the most efficient residential solar panels with lowest degradation and best performance warranty, so it’s hard to disagree.

SunPower started in a lab in the early 80’s and officially became SunPower in 1988. After securing funding from investors the R & D team developed record breaking PV cells using advanced cell technology (which were used by the NASA space program) along with Honda to win the world solar challenge car race in Australia. These achievements put SunPower on the world stage as one of the leading solar cell manufacturers, plus layed the foundation for the high-efficiency Maxeon IBC cells used today.

SunPower cells used on the SolarStratos solar powered aircraft - Image credit SunPower Corp

SunPower cells used on the SolarStratos solar powered aircraft - Image credit SunPower Corp

During the 2000s SunPower expanded and built advanced facilities in the US, Mexico, Europe and Asia to manufacture high efficiency solar panels. Over the last decade the only other manufacturer able to compete at the same level of efficiency and performance was LG Energy with the Neon R range of panels which use a similar IBC cell technology.

However, it hasn’t all been smooth sailing for SunPower. Over recent years the company ran into serious financial issues and racked up a considerable level of debt due to high overhead costs and pressure from the extremely competitive Chinese and Korean panel manufacturers. The financial troubles forced SunPower to restructure its business and manufacturing operations and now the financial situation is looking more positive. See detailed company analysis in this article from PV-Tech.


SunPower Panel and Cell Technology

Maxeon IBC cells

SunPower began mass production of the high-performance IBC (Interdigitated Back Contact) cells back in 2007 and have led the industry ever since using what is considered the most efficient cell technology available today. Unlike the common monocrystalline and polycrystalline solar cells which use front mounted busbars and fingers to collect current, IBC cells have a fine grid of conductors integrated into the rear side of the cell. The IBC cell design which SunPower refers to as ‘Maxeon’ uses a grid of N-type and P-type silicon on the rear side which increases efficiency by eliminating the need for front exposed busbars which partially shade the cell. The SunPower IBC cells are built on a base of high purity N-type silicon which also increases performance and has the low degradation rate which is how SunPower can offer the leading performance warranty of 92% retained capacity after 25 years on both the E series and X series.

SunPower Maxeon IBC cells used on the X series panels - Image credit Sunpower Corp

The current generation 3 and 4 IBC cells from SunPower are the smaller format 5” (125mm x 125mm) size and configured in a 96-cell layout with 8 rows of 12 cells. Almost all other manufacturers have moved to the 6” (156mm x 156mm) cell size which make up the common 60 cell panel. Cell size doesn’t affect performance but more cells does equate to a higher voltage which can be problematic for domestic installations which can have a voltage limit of 600V (depending on country). A higher voltage means less panels can be linked together in a string before the upper voltage limit is reached.

Shingled Cells

Shingled cells are an emerging technology which use overlapping thin cell strips assembled horizontally or vertically across the panel. The SunPower P series panels uses the vertical format with 6 long cells in parallel which offered additional shade tolerance when partially shaded as each long cell works independently. The thin singled cells are also more flexible and less prone to micro-cracking which is a common issue with conventional full size square cells. These are made by laser cutting a normal full size cell in to 5 or 6 strips and layering them in a shingle configuration using rear side connection adhesive. The slight overlap of each cell strip hides a single busbar which interconnects the cell strips. This unique design covers more of the panel surface area as it doesn’t require front side busbar connections which partially shade the cell, thus increasing the panel efficiency much like IBC cells.

SunPower P series panels use P-type shingled cells - Image credit SunPower Corp

SunPower P series Shingled cell construction - Image credit SunPower Corp

The P series uses conventional P-type silicon cells which although not as efficient as the high performance N-type are much more cost-effective but still achieve a high efficiency of 19%. Backed by the SunPower 25 manufacturer’s warranty.


The SunPower Range of Panels

With the addition of the Performance P series SunPower now have a more diverse range of panels for residential and commercial applications. The top of the line E and X series use the high efficiency IBC cells compete in the premium end of the market while the more price competitive performance P-series using the overlapping shingle cell design complete more in the commercial market.

X Series

SunPower X series panel.jpg

The X series is the flag ship of the SunPower range and is available in a range of models for both residential and commercial installations. The model numbers represent the efficiency with the base model X20 being just over 20% efficient, the X21 with a maximum of 21.4% efficiency and finally the X22 tops the range with an impressive 22.2% maximum efficiency.

The current X-series utilises a less common 96 cell format using smaller high grade ‘Maxeon’ IBC cells with the lowest rate of degradation and best 25-year performance warranty today. The SunPower Maxeon IBC cells have an outstanding warranty with a guarantee of 92% retained capacity after 25 years of use.

  • X22 series – 96 cell – 360 to 370W - Monocrystalline IBC N-type

  • X21 series – 96 cell – 340W - Monocrystalline IBC N-type

E Series

Sunpower E series solar panel.png

The E series from SunPower uses the previous generation Maxeon IBC cells which are slightly less efficient but are still based on the long-lasting N-type silicon substrate and offer an extremely high-performance warranty with an impressive 88% retained power rating after 25 years.

Like the X series the E20 model name refers to the efficiency with a power rating of 327W and a panel efficiency of 20.1%, making it still one of the most efficient panels available.

  • E20 series – 96 cell – 327W - Monocrystalline IBC N-type

P Series

As described in detail earlier the Performance or P series panels use the unique shingled cell design with 6 long cells in parallel. This design offers are most more cost effective and offer additional shade tolerance when partially shaded. The thin singled PERC cells based on the common P-type silicon are also more flexible and less prone to micro-cracking which is a common issue with conventional full-size square cells.

Despite being based on standard P-type silicon SunPower still offers an impressive 25 year performance warranty as well as a 25 year manufacturer’s warranty.

  • P19 series – Shingled cell – 385W - Monocrystalline P-type

SunPower P series Shingled cell panel.jpg

A Series

Next Generation Technology

SunPower announced early in 2019 its latest generation A series panels using what it has termed the NGT or Next Generation Technology IBC (Interdigitated Back Contact) 'Maxeon Gen 5' cells. These new larger formats 6” cells will be fabricated on a new line at its manufacturing plant in Malaysia.

The new design will be assembled into an impressively powerful 400W panel which will be the highest rated residential panel available. However, in an unusual move the A series will incorporate a micro inverter from Enphase energy and will only be available in the US market. It is expected to be available internationally once the production volume increases and the older E series lines are upgraded to the new larger format.

  • A22 series – 66 cell – 400 to 415W - Monocrystalline IBC N-type (Gen 5)

COMING SOON


Warranty and service

SunPower offer a leading performance warranty on the E and X series which both utilise the Maxeon IBC cells based on N-type silicon. The X series has an outstanding warranty with a guarantee of 92% retained capacity after 25 years of use.

The exact warranty details from the SunPower warranty certificate are as follows: “The power of the PV Modules will be at least 98% of the Minimum Peak Power2 rating for the first year, and will decline by no more than 0.25% per year for the following 24 years, so the power output at the end of the final year of the 25th year warranty period will be at least 92% of the Minimum Peak Power rating (the “Guaranteed Peak Power” rating)”

See the full SunPower warranty certificate here.


Sustainability

Cradle to cradle certified

The SunPower E-Series and X-Series Panels made in Mexico and France are the world's first solar panels to be Cradle to Cradle CertifiedTM which makes SunPower the worlds leading manufacturer when it comes to sustainability.

SunPower Cradle to Cradle certified 2.jpg

See the full detail about the SunPower cradle to cradle certification here


Conclusion

SunPower is still regarded as the top solar panel producer with only a few manufacturers competing at the same level of performance and quality. In terms of outright efficiency SunPower still leads the world with the X series being the most efficient solar panel with lowest degradation and best performance warranty on the market. Although not surprisingly the X series is also the most expensive panel on the market, but like most things quality comes at a price. Considering solar is a long-term investment, the higher price also equates to better performance with more energy generation over the life of the system.

The financial issues faced by SunPower over recent years has raised some concerns over the ability for SunPower to honor the long-term warranty commitments, but despite this SunPower is still ranked as number one in the US and many parts of the world by installers and customers alike. In contrast the limited supply and distribution in other markets like Asia and Australia, SunPower does not have a large presence and the very high price of the E and X series can be difficult to justify when other manufacturer’s can offer similar performance and quality at a lower price.

The new P series on the other hand has been very successful in the commercial solar sector being most more cost-effective and backed by one of the best warranties available. With the financial outlook improving and the next generation A series panels coming in 2019 it looks like SunPower may continue to be an industry leader for some time to come.