It’s no secret that SunPower produce some of the most efficient solar panels available and be certain, the SunPower X-Series is at the top of the chain when it comes to high powered performance.  Fact is if you require the superior performance, it’s going to cost more than most. In fact, more than all other commercially available solar panels. That aside the question still beckons, is the SunPower X-Series the right solar panel for your installation?


Make and model:  Sunpower X-Series.

Variants:  350 / 360 / 370 W.

  Almost everything.

  Unaffordable for most.

No matter how good a particular solar panel is acclaimed to be, there are often six main psychological decision-making traits which the end user, whether consciously or not, will ultimately base a buying decision. Design, durability, efficiency, performance, guarantee and most importantly, affordability all play a part in deciding whether the Sunpower X-Series is the right solar panel for your installation. 

The more interesting element particularly is, how will the Sunpower X-Series affordability score impact the overall technology score? Hint – It hurts.


To see how the Sunpower X-Series ranks in the Solar Review Module Assessment Criteria be sure to view the scorecard at the bottom of this post!


The Sunpower X-Series is designed with simplicity in mind although very technically adverse. Fewer panels, more power. Sunpower has always done things a little differently though, and the Sunpower X-series is no exception when compared to a 60-cell conventional solar panel design (closest equivalent). A slightly wider 1046mm and slighter smaller 1558mm panel dimension accommodates 96 monocrystalline Maxeon Gen 3 solar cells, and the formula works well.

Sunpower’s patented solid metal back contact cell design ensures the most amount of available sunlight gets converted into electrical energy with no busbars on the front of the cell obstructing available light. Added strength is assured through a sturdy 46mm, dual wall, class 1 black anodised aluminium frame. A lower profile would assist a more aesthetically nice design. However, you can’t argue when one of the best product warranties available.

Download the SunPower X-Series datasheet here:

Sunpower X-Series Solar Module Image


X-Series Design; Outstanding
  • N-Type mono cell.
  • Rear contact connection.
  • Rear contact enhanced.
  • Glass-laminate (White).
  • Innovative.
  • InterSolar award.
  • TÜV Reihnland certified.


Equipped with all the required durability ratings, the Sunpower X-Series isn’t the most durable solar panel available when compared to alternative solar panels by alternative high-end manufacturers. The SunPower X-Series will, however, withstand most environments with certified resistance to ammonia (agriculture), hot & cold cycles (desert) and salt spray (coastal). Impact resistance is passable factoring hailstones of up to 25mm and the wind loading is adequate but lacking towards alternative offerings.

An extraordinary amount of research and development has been incorporated toward achieving the highest efficiencies within the SunPower X-Series. Although, that R&D tends to lag behind competing brands within the realms of durability. It would be a shame to see a SunPower X-Series product warranty not upheld due to adverse environmental impact.

Sunpower X-Series Solar Module Image


X-Series Features; Elite
  • Snow load 6000Pa.
  • Front wind load 6000Pa.
  • Rear wind load 3000Pa.
  • Damp heat testing 6000Hrs.
  • Thermal cycle testing 800+Hrs.
  • PID Free.
  • Salt mist IEC 61701 (Severity 6).
  • Amonia resistance IEC 62716.
  • 25mm hail impact.


SunPower X Series modules achieve an outstanding peak efficiency of up to 22.7% delivering a power output of up to 370W (+5/0%). An outstanding Temperature coefficient further enhances efficiency. Lower the better the temperature coefficient is a remarkable -0.29%/C. (Tier-1 average -0.40%/C).

Sunpower X-Series Solar Module Image


X-Series Efficiency; Outstanding
  • 22.7% Maximum module efficiency.
  • -0.29%°C Temperature coefficient.
  • +5/0% Power tolerance.


Whoever thought that solar cell degradation would be such a talking point? Consider the amount of degradation defines performance over time, now it becomes interesting. The Sunpower X-series degrades at a mere 0.25% per annum after the first year (2% year-1). A remarkable quality which ranks as the lowest rate of power degradation from any manufactured solar panel. With such a reduced rate, the expected power output after 25 years for the SunPower’s X Series is 92%. The lowest rate of degradation in a solar panel we’ve seen.

Sunpower X-Series Solar Module Image


X-Series Performance; Outstanding
  • 2% degradation in the 1st year.
  • 0.2% degradation per annum.
  • 25-year linear performance warranty.
  • Parts and service warranty.


Respected in anyone’s eyes is a comprehensive product guarantee and the SunPower X-Series delivers over 25-years. Product, performance and labour are all considered should the solar module not live up to the promise. Such an extensive warranty puts the SunPower X-Series warranty within the top 3 solar panel warranties available. Just be sure to match the SunPower X-Series with the right environment as the acclaimed product warranty may become obsolete in certain conditions.

Sunpower X-Series Solar Module Image


X-Series Guarantee; Outstanding
  • 25-year warranty.
  • Parts & service warranty.
  • Authorised installer network with no additional end-user benefits.



X-Series Overall; Outstanding
  • Design 4.9
  • Durability 4.6
  • Efficiency 5.0
  • Performance 4.8
  • Guarantee 4.8


How was the score for the Sunpower X-Series range of solar panels calculated? By utilising the Solar Review Module Assessment Criteria V2.3 >


  1. I just installed a grid-tied system with 45 of these, SolarEdge power inverters on each, and all tied to two SolarEdge HDwave inverters (7600H-UD). Installed and commissioned it cost $50,700, rated at 16.65 kWp. As I have an EV and plan on buying another, I wanted a system that would produce all of my vehicle’s energy along with everything else in the house, and eventually get batteries and a grid cut off to live off the grid during outages. I looked at cheaper panels but decided the degradation of these were so good that I wouldn’t have to worry about needing to rework the system in 10 years when other panels would hit 8% or more degradation and start affecting my total production enough so that it would start hurting.

    Given that it is impossible to find out how much these panels actually cost, all I could do was price the cost of the other major parts and factor backwards. Note that the price I gave included installation and commissioning, and all the other hardware and labor needed. The power optimizers and 2 inverters, when I shopped around, ended up costing about $8,100 retail. The mounting brackets and other hardware looked to cost another $1,500. Sales taxes would be $576. I have no idea how much the labor and design costs were, but the installation took a 3 man crew 4 days. Estimating $40/hr * 3 people * 4 days = $3,840 (this could be drastically lowballing the labor costs). So that is $14,016 there. That leaves $36,684. Taking away sales tax of $2,201, the price for all the panels looks to be $34,483. That means the panels are $767 each, more or less.

    Casually looking for solar panels that would compete with the 370w performance, I’m seeing stuff around $250-$400. Of course many of these panels don’t have high ratings, and none have the efficiency or low degradation of these panels. Overall, I’m pretty happy with its performance and looks, and the fact that I will never pay for gas again along with having negative electricity bills. I just wonder if anyone has any insights on if the degradation and performance was a good deal or not for me overall? Frankly the biggest reason I got these was because Tesla still wasn’t selling in my area, and I wanted to get grandfathered in before my utility dropped the net metering payments to a third of what they are now. So I bought big and installed before the change so I can maximize the return and minimize how much I bought for transportation. I would like to hear from others on this, and have this help people considering getting these high-performance but expensive panels.


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