SunPower Solar Panels: One of the best panels lots of money can buy

sunpower solar panels

SunPower make very good, very expensive panels.

SunPower make some of the best solar panels in existence. Or at least some of the best on this planet. Perhaps Spectrolab regularly shoots better ones into space to mars or somewhere, I don’t know. But if you want to buy something that is meant to go on a roof and not a space probe, then SunPower solar panels are hard to beat.

Now note that I did say some of the best and not some of the cheapest. If you haven’t worked out that the words cheap and best don’t normally go together, then I have a really low quality laptop held together with superglue and wooden rulers that I’d like to sell to you at a really high price.

SunPower Pricing

So let’s deal with the elephant in the room right now: the SunPower solar panels’ price. SunPower are one of about 30 panel brands that are called “Tier 1”. 1 Eighty percent of Tier 1 panels are made in China and are all sold in Australia at a very similar price per Watt. Examples include Trina, Jinko, Risen, Renesola, JA Solar and Canadian Solar.

If you want to go up a notch in price, performance and durability, you are looking at what I call ‘Premium Tier 1’ brands. These include LG, Q-Cells, Solarworld, REC and Winaico. These generally sell for around 30% more than the regular Tier 1 brands.

All on its own at the top of the price list are SunPower Solar Panels, costing 75-100% more than a regular Tier 1 panel.

sunpower cost

SunPower Solar Panels Price Relative to other brands

But if you want Rolls-Royce quality, you have to pay for it, and on Friday I sat down to have a little chat with Chris O’Brien, the Managing Director of SunPower Australia.  I wanted to find out why people are prepared to almost pay twice as much for SunPower compared to a typical Chinese Tier 1 brand.

What The Hell Is SunPower?

SunPower is a US company that produces panels in the Philippines, presumably because they saw the people there badly needed a boost to their low wages.

The company was founded in 1985 by Richard Swanson, who first started investigating solar cells because he was fascinated with their use in space.  The company spent $6 million developing space solar cells, but they were not a success and I couldn’t find a single example of their solar cells being blasted into orbit or beyond.  I’m afraid Spectrolab pretty much has the space solar market stitched up.  But I think SunPower deserves credit for trying.  Personally, I wouldn’t compete against Spectrolab in anything, as they are clearly winner of the prize for having the company name that makes them sound most likely to attempt to kill James Bond.

James Bond: Everything he touches turns to excitement. And a little while later a rash

SpectroLab: They have a James Bond name and they beat SunPower in the solar space race.

Richard Swanson is also famous for Swanson’s Law, which states that for every doubling of production capability, the cost of solar panels fall by 20%. And while the price of solar panels have had their ups and mostly downs, his law has done fairly well.  So let’s all hope solar panels have a few more Swansons left in them.

SunPower’s Warranty Is The Best You Can Get

SunPower sell panels with a 25 year warranty. And that’s not just the performance warranty. I can buy cruddy solar panels from a company with an internet site that claims a photograph of an architect’s model is their factory and they will come with a 25 year performance warranty. While SunPower does have a 25 year performance warranty, I’m talking about their product warranty. That’s what’s important, because if your solar panel stops working, the performance warranty won’t cover that.  Only the product warranty does and SunPower Australia’s is 25 years, which is more than twice as long as the next best I am aware of.

SunPower’s failure rate is 27 in 1 million. That means only one panel in 37,000 is defective and needs to be replaced. So if you have a rooftop solar system of around 5 kilowatts with 15 panels, that means there is about one chance in 2,500 you will have a defective panel that needs to be returned. And those are damn good odds.

Did I say return a panel? Actually, there is absolutely no need to return it.  If you have a defective panel, SunPower will send someone to come and replace it.  Now that is good service.  And presumably they will take the old panel away and perform an autopsy to determine why it died so young and take steps to try to ensure it never happens again.

How Do They Offer Twice The Warranty Of Anyone Else?

Thermal expansion is a major cause of solar panel failure.  It results from temperature changes causing different materials to expand and contract at varying rates and puts strain on joins between different materials and can cause cracks to form in the thin metal wires that conduct electricity.  Once those wires break and stop the flow of current they can form a hot spot that gradually burns through the protective encapsulate that covers it, which can lead to corrosion and the failure of the entire panel.

SunPower claim to have completely eliminated thermal expansion as a cause of failure, for at least the first 25 years of their panel’s life.

They have done this by making the wires that collect electricity a fine patterned mesh on the back of the cell, which resembles a printed circuit board.  And this arrangement is apparently great at distributing stress caused by expansion and helps keep it together.

They have also greatly improved the survivability of connections between solar cells by having more of them and designing them so they suffer less stress from thermal expansion.

The panels also have a thin copper backing. Copper is a soft, ductile metal useful for avoiding damage from thermal expansion and it is also excellent for resisting corrosion. Unfortunately, copper is expensive, so perhaps they could benefit from using a different material. Looking up the periodic table, as I do at regular intervals, I see that elements with properties similar to copper are silver, gold, and something called roentgenium which decays so fast it has severe trouble lasting 25 minutes let alone 25 years. So maybe copper is a good choice.

sunpower solar panels' cell structure

SunPower cells have a copper plate on the bottom and a light trapping surface on the top.

Interestingly one of SunPower’s competitors in the premium solar panel market, Q-Cells are working on a cell design (codename: Q.ANTUM) that appears to be ‘inspired’ by SunPower but uses aluminium instead of copper, and has the reflector layer under the silicon:

q-cells q.antum cell

Q-Cells appear to be moving to a Sunpower style back contact, but they have chosen aluminium.

Aluminium is much cheaper than copper – so it will be interesting to see how the final Q-Cells Q.antum panels compare in performance, durability and price. Watch this space I’ll let you know as soon as I can get more information.

SunPower Panels Produce More Electricity Per Watt Than Most

SunPower panels are extremely reliable, but in addition, they claim to produce more energy over the course of their lifespan than many other panels. They achieve this in several ways.

  • They have positive tolerance which means the panels always produce at least as much power or more as their rating when they are new.  Never any of this plus or minus business.
  • They have no wires on the surface of the cell to block sunlight.
  • The panels are better at handling shade than standard panels.
  • They operate at a lower temperature which improves their performance.
  • They degrade more slowly than other panels.

Positive Tolerance

Solar panels vary in their output. No manufacturing process is so precise it can make perfectly identical panels.  Not even SunPower can achieve that.  But if you buy a 345 watt SunPower panel, you will be getting a panel that produces 345 watts plus 0 to 5%. That is, 345 watts is the absolute minimum. So any variation in output will end up favoring you.

Positive tolerance, where there is no downside, is not uncommon among high quality panels, but there are still many that have their tolerance as plus or minus a certain percentage. One of these panels could produce more than its rating, but it is just as likely to produce less. And then there are the dodgy panels that say they have positive tolerance but lie and their actual output can be all over the place.

Nothing Up Top

The surface of SunPower cells are completely nude. There is nothing there to block sunlight from hitting silicon. Many other manufacturers, but certainly not all, place a grid of fine, flat wires on top called the busbar to collect electricity, while on SunPower cells all the wires all go underneath. The difference between the two types looks like this:

a conventional poly crystalline cell and a cell used in sunpower solar panels

The difference between a solar cell with wires on top and a topless one. Yes, I broke the cell on the left. It’s not my fault I have eight thumbs and two fingers. I also smudged the one on the right with my thumbs.

Putting wires on top is easier to do and saves money, and there is nothing wrong with saving money, but from a purely energy efficiency point of view it’s a really bad design choice. It makes as much sense as if the vessels that supply blood to the light sensitive cells in our eyes passed in front of the retina instead of behind it. Wait a minute, that actually is how our eyes work. I think I have just said that SunPower is a better designer than God.

Shading caused by wires on top is worse when sunlight is striking it at a shallow angle, so for north facing systems SunPower panels will tend to tend to perform better in the early morning and late afternoon than panels that aren’t topless.

SunPower Solar Panels & Shade

Solar panels don’t like shade. The obvious problem is less sunlight energy hits the panel and no amount of design ingenuity can get around that. But there is the bigger problem that shading one small part of a panel can cause the output of the entire panel to fall, and if multiple panels are all connected to one inverter, as they usually are, one shaded panel can bring down the output of the entire string of panels.

This problem is reduced through the use of diodes which typically divide the panel into three, so if bird poop lands on one section the diodes can bypass that part and only cut the panel’s output by a third.  SunPower doesn’t divide panels into three, they have diodes on every single solar cell in the panel. And they have the advantage of not using physical diodes. So I guess this means they must be using some kind of spiritual diode.

This is important because physical diodes have a limited lifespan. While there are plenty of diodes in the world that have a Mean Time To Failure of 10,000 hours or more, the ones in many cheaper solar panels can be shot after 1,000 hours of use. So if a panel is shaded for three hours a day, its diodes could be useless after one year. In fact, some cheap and nasty panels can have their diodes shot when they are installed.  And this is something people won’t know unless they test them, and someone installing shonky panels isn’t likely to, (a) bother to test them, or, (b) tell you they got a bad result even if they did test them.

Check Out The Temperature Coefficient! These Are Some Cool Panels

The hotter silicon PV gets, the less electricity it will produce. That’s just the nature of the beast. It’s not like paper where if you get it up to Fahrenheit 451 it will suddenly give off a lot energy by bursting into flame. Or rather, Fahrenheit 842, as paper’s flashpoint is actually 451 degrees Celsius.2  It appears Ray Bradbury didn’t even bother to check the internet when he wrote Fahrenheit 451 back in 1953. What a lazy hack.

But highly efficient solar cells have a virtuous circle going where the more sunlight they convert into electrical energy, the less waste heat is left over to make the panels hotter. This is the opposite of a vicious circle, which is like Pac-Man when he gets drunk after a hard day of eating dots.

As a result of this, and also because the copper backing is also good at whisking heat away from the cells, these panels can run up to three degrees cooler than a run-of-the-mill panel, which results in higher efficiency.

Note this effect won’t result in extra electrical production above its rating. It is included when the panel’s rating is determined, but it will cause them to degrade at a slower rate, because the lower the temperature the slower materials decay.

SunPower panels vary in their ability to resist the effects of heat.  Typical panels will have their output reduced by about 0.4% for each degree rise in temperature.  The 20% efficient SunPower E series panels will have their performance reduced by 0.38%, which is okay.  And the 21% efficient SunPower X series panels will have their output reduced by about 0.3%, which is quite good.

SunPower Panels Degrade Slowly

Because SunPower panels are so good at keeping it together and not suffering from the effects of thermal expansion and because they are cooler than most panels, they degrade very slowly and so the fall in their output over time is very gradual.

Their warranty covers a 0.4% decline in output per year. So if you buy a 345 watt panel from SunPower Australia after 10 years it will still produce over 331 watts or they will replace it.  But the warranty is always going to be greater than the average actual decline, or it will be for any company that wants to stay in business, and I have been told the real world degradation of actual panels on roofs and in solar farms is 0.12%, which is excellent. So after 10 years you can expect your 345 watt SunPower panel to still be producing around 341 watts.

Who Should Buy SunPower Panels?

Unfortunately, SunPower panels are not cheap. They are roughly twice as expensive as conventional panels. But that’s just the way things are. If you want quality, you have to pay for it. And taking the long term view, if they produce 20% more electricity over 25 years then they are worth 20% more. And because SunPower will send someone to replace any panel that fails within its 25 years product warranty, that’s worth money too, as well as peace of mind. And if you take a very long term view, I feel confident there will still be plenty of SunPower panels continuing to operate after 50 years of use.

I think there are three basic types of people who would be interested in panels from SunPower Australia:

(1) People who value having the best technology available:  If you don’t care about paying more to get the most advanced panels and you want to aid technological progress by rewarding manufacturers who make the best products, then these panels are for you.

(2) People who value reliability:  If you want a rooftop solar system you can just, “fire and forget” and be extremely confident that you won’t have any problems with your panels for at least quarter of a century, then these panels are for you.

(3) People who are snobs.

There are plenty of people who will fit into the first two categories of wanting the best technology or an extremely reliable system. Our SunPower reviews give lots of examples of happy Australian customers who fit these 2 categories.

And there are also plenty of people who will fit into the third category. And if you are a snob that doesn’t know a damn thing about solar panels, but just know that you want the most expensive, that’s fine! There’s nothing wrong with being a snob! Or at least, that’s what my friend Gina told me on her yacht this weekend when we were spearfishing for poor people.

Future Developments

The E series which is about 20% efficient is currently available from SunPower Australia, as is the X series 345 watt panel, which is 21.5% efficient. And they will have a new type of panel which has lower efficiency, but is lower in cost while having the same utterly impressive 25 year product warranty, available at the end of 2016.

And I will tell you all about those panels as soon as they are released. Promise.

Footnotes

  1.  Tier 1 is not a direct measure of quality. It is primarily based on whether the banks trust the brands enough to make large loans to solar developers who want to use the brands. But in my opinion, buying Tier 1 is the best way to reduce the risk of buying a crappy brand.
  2. As Tom has pointed out in the comments, Ray Bradbury was pretty much correct when he gave Fahrenheit 451 as the flash point of paper.  The 450 Celsius figure I found on the internet is actually an outlier.  So Ray Bradbury back in 1953 with no internet was right and I was wrong.
About Ronald Brakels

Many years ago now, Ronald Brakels was born in Toowoomba. He first rose to international prominence when his township took up a collection to send him to Japan, which was the furthest they could manage with the money they raised. He became passionately interested in environmental matters upon his return to Australia when the local Mayor met him at the airport and explained it was far too dangerous for him to return to Toowoomba on account of climate change and mutant attack goats. Ronald then moved to a property in the Adelaide Hills where he now lives with his horse, Tonto 23.

Comments

  1. Peter T says:

    G’day Ron, many thanks for a very informative article. Whilst I had some appreciation of the quality of Sunpower panels and their cost, I did not know about the finer detail surrounding cell interconnection and panel construction.

    In regards to aluminum back contacts, well I would caution against its use because Telstra used aluminum telephone trunk wiring back in the 1970s to alleviate the then cost if copper, but 30 years later, under a major Y2K remediation project I was involved with, all that wiring had to be replaced because it had become severely oxidized and brittle, thereby reducing its conductivity and serviceably considerably.

    Again, many thanks!

    • Ronald Brakels says:

      Thanks for the kind words, Peter, and thanks for the insight into what happens to aluminium wiring after 30 years. Aluminium does seem to be the poor man’s copper, as whenever the price gap between them grows it is substituted for it, with varying degrees of success.

      But copper prices have fallen to a 7 year low, which will reduce attempts to replace it with aluminium and help reduce SunPower’s costs. And it will also shave a little off the cost of wind turbines and electric cars.

  2. Nice piece.

    QCELLS Q.ANTAUMs are already on sale in Australia, the Q.PLUS range.

  3. Tom Martin says:

    Ron,
    Thanks for interesting article. It appears that the Panasonic 325w HIT panel is quite comparable in regards to specs but significantly cheaper. What do you think of it compared to the sunpower?
    Cheers

    • Ronald Brakels says:

      Hi Tom, I haven’t had anything to do with Panasonic 325w HIT panels myself, but everything I have heard is good. However, they are very rare in Australia and may be hard to find. What impresses me is I just found out they offer a 15 year product warranty, which as far as I know is the second best in the industry.

  4. Tom Conner says:

    Great Article Ronald, it furthers my resolve to choose Sunpower panels for the zero energy residence I am currently building. I also really appreciate your humor throughout.

    PS – I think you were joking about Ray Bradbury being incorrect about the flashpoint of paper…? But it did compel me to look it up and confirm that he was pretty darn close: https://en.wikipedia.org/wiki/Autoignition_temperature#Autoignition_point_of_selected_substances

  5. Tom Conner says:

    No worries Ronald, keep up the excellent and funny writing.

  6. MatthewCooper says:

    Out of curiosity, where would Yingli panles go in the scheme of things?
    would be good to see a list of the tier 1 break up (standard vs premium)

    • Ronald Brakels says:

      Yingli makes tier one panels with a 10 year product warranty, which is standard. As for tier one panels that could be considered to be premium, I can think of three off the top of my head that have product warranties longer than the standard 10 years. Hanwa Q Cells Q.ANTUM line of solar panels have 12 years, Panasonic has 15, and SunPower is the champion of warranties with their product warranty equal to their performance warranty of 25 years.

  7. I was given a few quotes to start up with solar panels. One supplied Seraphim 260W panels and the other SAID they supplied tier 1 Australian made Matrix solar panels. What is your opinion on these?

    • Seraphim are a reasonable Tier 1 panel.

      I don’t know about Matrix – it’s a pretty obscure brand – they are not Tier 1 on any list I’ve ever seen.

  8. Which would you choose Sunpower or LG? LG appear to be newer technology but Sunpower good write up too!

    • Hi I am also interested on which panels would be a better choice:

      Sunpower E20 327W or LG Neon2 330W ?

      • Ronald Brakels says:

        They are both very good panels. SunPower provides a 25 year product warranty while the LG NeON 2 has 12 years. (Looking at its datasheet, the LG NeON 2 has a maximum of 320 watts.) Their efficiencies are similar with the SunPower E20 at around 20% and the 320 LG NeON 2 at 20.8%.

        The good news is you are extremely unlikely to need to use the warranty for either.

  9. david warren says:

    Hi Ronald. I just checked the warranty on sunpower E20 panels and the product warranty is only 10 years not 25 years.

    • Ronald Brakels says:

      I suspect the information you have isn’t correct, David. The Australian SunPower site says their E20 panels have a 25 year warranty and it is clearly stated on their datasheets. I’d be very surprised if it’s not actually 25 years.

      • David Warren says:

        Ronald. I am holding in my hand the data sheet for sunpower E20/333 and E20/327 solar panels.
        under the warranty and certifications it clearly states ,and I quote:-
        warranties. ’25 year limited power warranty’
        ’10 year limited product warranty;

      • David Warren says:

        Hi Ronald. My apologies to you. I am now holding another sun power sheet which confirms what you say about sun power panels. 25 year power and product warranties. perhaps the original was one of those items that gets left floating in cyber space. It has a 2011 date in very fine print in the lower left hand corner.

  10. Dr. Work says:

    Two minor points: The grid of silver “wires” (which are lines screen printed onto the cells) on typical solar cells is made up of wide bus bars and narrow fingers. Not all the silver lines are bus bars, just the wide ones.

    You are confusing flashpoint with auto-ignition point. Bradbury never said the flashpoint of book paper was 451F. He was referring to the auto-ignition point. The flashpoint of something is when it is hot enough to produce enough vapors to support combustion from an external source. The auto-ignition point is when a material spontaneously bursts into flame. Whether 451F is correct for the auto-ignition point of book paper, that is a whole different debate, and will depend very much on what precisely you mean by book paper (and I don’t want to get into that debate!).

    Another advantage that Sunpower cells have over mass-market cells is that they are n-type (phosphorus doped in their bases) rather than p-type (boron doped in their bases), which means they don’t suffer from light-induced degradation when put into the field. LID (light-induced degradation) is caused by B-O defects which are activated by sunlight. P-type cell manufacturers have started taking steps to reduce LID, but no one knows if these fixes will last for the lifetime of the panel in the field.

Speak Your Mind

*

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Subscribe!