Most Efficient Solar Panels

by Shawn Roe | 88 Comments

Solar Efficiency Basics TiersCompareMost EfficientTable

Two great questions many people ask about solar panels are: “Which panels have the highest efficiency?” and, “Which solar PV panels are the best?” Keep reading if you’re looking for the most efficient solar panels.

This solar power panel comparison chart below compares the solar panel efficiency of the most popular 200 W solar panels.  All of the modules on this chart are rated at 200 Watts, which means in strict laboratory conditions, they produce the same output. However, because solar panels vary in size, some are more efficient compared to others. Sanyo, SunPower, Trina, Canadian Solar, Suntech and the others are common solar panel manufacturers used by installers in the US.

(Updated 6.26.2013) Chart of most efficient solar panels rated at 200 watts.

Of the highest output panels, both Sanyo and SunPower panels have the highest efficiency per surface area in real world conditions. Given a limited roof area with which to install solar panels, these panels are the best choice to produce the most electric output per square foot. However, this doesn’t mean that these panels will always be the best choice. Well, how should you choose solar panels then? Here are 5 questions to ask your installer before going solar.

The chart below shows some of the most common and efficient solar power panels (rated at 220 W) on the market and listed on the State of California’s “List of Eligible SB1 Guidelines Compliant Photovoltaic Modules” as of June 26, 2013. Char of most efficient solar panels rated at 220 watts.

So, if I know the most efficient solar panels, then I know which solar panels are the best, right? Well, if efficiency is all you care about, then yes.  But efficiency is often not the most important factor.

Some solar installers will try to sell you on the fact that their panels are ‘more efficient’ than other’s. Don’t worry too much about efficiency though. There’s a better way to compare which complete solar system is best for you. Choose the system with the best value. You can read about solar value here.

So, you know which are the most efficient of the common panels. But, which are the most efficient of them all? Continue to the solar panel comparison table with over 13,000 panels compared side-by-side!

Chart Key:

  • Manufacturer = Solar Company; Brand
  • ID = Specific solar module identification code; module name
  • Rating = Standard Testing Conditions Rating; nameplate rating under laboratory conditions
  • Efficiency (%) = Output per input light irradiance using STC; energy conversion efficiency; module efficiency
  • Tier = Solar Panel Efficiency Tier. 1 is highest, 5 is lowest

88 comments on “Most Efficient Solar Panels

  1. Ok…so im confused. Is a 200W Sanyo Panel the equivalent of say a 240 Evergreen based on its efficiency? If I install a 5KW system with 200W Sanyos or 240 Watt Evergreens – which system would produce more during the course of the year?
    thx great website. Add more for us dummy laymen types!

    1. Great questions Gordo. Generally, the PTC rating of the module (solar panel) is the best way to compare which panel will produce more during the course of the year. The PTC rating is a more realistic rating of the panels tested under real-world conditions as opposed to laboratory conditions.

      Each 5 kW system will produce slightly different depending on many things (tilt, direction, shade, etc). The easiest way to compare systems is to have different solar companies give you free evaluations (proposals) on a system. After they explain everything, ask them what the “expected first-year output in kWh’s” is, and then you can see which system will produce more during the course of a year.

      What kind of information can I add to help the dummy laymen types? I’m open to suggestions. My goal is to simplify solar as much as possible. Thanks for the comment!

  2. I’ve been talking to a local solar company, but I don’t feel I have quite enough information to take the solar leap. Some questions:
    I’m looking at three systems; a Sunpower 235wt (24 panels), a Sunpower 210wt sytem (24 panels), and a Sharp 235wt sytem (22 panels). These are arranged in most-to-least expensive. Net costs after rebates, taxes,etc. range from about $24,000.00 to $22,000.00 to $19,000.00
    One thing none of your charts considers is aesthetics. The all-black Sunpower panels are a lot better looking than the Sharps, and in this situation quite important. So, am I foolish looking at the more expensive systems, or does anyone else make a good-looking product?
    How much wiggle room is there in these quotes? This cliff is pretty steep. I don’t know if I should jump now or wait until other companies come up with less industrial-looking systems.
    Thanks for your imput Rick

    1. Glad to hear that you’re talking with a local installer. You’re correct: my charts do not include aesthetics. Beauty is in the eye of the beholder, no? It would be hard to scientifically measure aesthetics. However, you’re not the only person who has considered the looks of the system. Looks actually ends up being an important factor for many people. Your major differences in price of these three systems are going to come from their output, not their looks.

      Sharp actually recently came out with the OnEnergy roof-mounted system with a “low-profile rack designed to blend beautifully with a home’s roofline”. Ask your installer if he can provide this system.

      The cliff’s not as steep as you think. Solar panels are going to look like solar panels. Companies are focusing on improving efficiency and reducing cost much more so than they are working on aesthetics. Don’t wait for that reason. Plus, the sooner you take the plunge, the sooner you’ll reap the benefits!

      As for wiggle-room, solar installers actually have low profit margins despite the news that it’s a booming business. The competition is strong (which is good for the consumer). The wiggle-room, if any, will be in the salesman’s commission. Talk to multiple installers, but remember – they’ve got to feed themselves too.

      Good luck Rick!

  3. I’m looking for the highest wattage per square foot, but the price on the 20% efficient sanyos are $4 per watt.. Is there anything more efficient than these yet as your post is getting old… The more wattage per square foot the better.I am going to cover a car with them as much as I can to run a hydrogen generator, and I will need as much power as i can possibly fit into that space.

    1. My charts are currently up-to-date. (This table is always up to date). There is nothing available on the market more efficient that what is listed. Anything more efficient has only been achieved in research laboratories and has yet to be available for the common consumer.

      I will be sure to update these charts when new efficiencies are reached. However, don’t expect this to happen regularly. Solar cells are not equivalent to computer chips. Let us know how the car progresses!

  4. Where does this data come from?
    Is it from the manufacturers, from a testing lab, or from real-world conditions?
    If it is from real-world conditions, which part of the real world? Was the testing done in New Mexico or Maine, or somewhere in between? And if so, does it cover a full year cycle? Were all of the panels tested at the same location?

    I know some panels behave better in low light conditions, some are more shade tolerant, heat tolerant etc. I would like to see some true side-by-side annual (or multi-year) results, especially if they come from the northeastern USA.

    1. This data comes from the List of Eligible SB1 Guidelines Compliant Photovoltaic Modules used to receive California state rebates related to solar installations. It is from PV USA Testing conditions performed at a research facility in Davis, California. California is by far the state with the most solar installations at more than 530 megawatts (MW). New Jersey and Colorado are a distant 2nd and 3rd with 70.2 MW, and 35.7 MW installed respectively (according this Reuters report). This is why the current data is from California, and not the Northeastern USA.

      The data is mainly for comparison purposes as the measurements are consistent. Local installers will have more information regarding local production output. My comparison charts are best used to confirm and/or ask about differences in output or efficiency.

      PTC refers to PVUSA Test Conditions, which were developed to test and compare PV systems as part of the PVUSA (Photovoltaics for Utility Scale Applications) project. PTC are 1,000 Watts per square meter solar irradiance, 20 degrees C air temperature, and wind speed of 1 meter per second at 10 meters above ground level. PV manufacturers use Standard Test Conditions, or STC, to rate their PV products. STC are 1,000 Watts per square meter solar irradiance, 25 degrees C cell temperature, air mass equal to 1.5, and ASTM G173-03 standard spectrum. The PTC rating, which is lower than the STC rating, is generally recognized as a more realistic measure of PV output because the test conditions better reflect “real-world” solar and climatic conditions, compared to the STC rating. All ratings in the list are DC (direct current) watts.

      Neither PTC nor STC account for all ‘real-world’ losses. Actual solar systems will produce lower outputs due to soiling, shading, module mismatch, wire losses, inverter and transformer losses, shortfalls in actual nameplate ratings, panel degradation over time, and high-temperature losses for arrays mounted close to or integrated within a roofline. These loss factors can vary by season, geographic location, mounting technique, azimuth, and array tilt.

      –from List of Eligible SB1 Guidelines Compliant Photovoltaic Modules

  5. I am confused. I live in So.Cal. and am getting estimates from 3 companies, the first, Solar City is going with the Kyocera panels (preliminarily), but I don’t see Kyocera listed on the California SB1 Compliant list. I also see that SunPower’s panels are more efficient. Since we are considering a PPA or lease, does it matter?

    1. Hi Jocelyn,

      It doesn’t matter. A solar leasing or PPA (power purchase agreement) installer like Solar City can use whatever panels they want, because they will own the system, which means they receive the rebate (not you). Several Kyocera panels are listed on the CA SB1 Compliant List, and if you were buying a solar system from an installer in California, you should make sure that your equipment makes you eligible for the rebates. But since it’s a PPA, it doesn’t matter for you.

      PPA’s or solar leasing are great ways to go solar, and as long as you feel you understand the terms and are getting a good deal (which you likely are) then you don’t need to worry about eligible or efficient equipment. You only buy the energy produced, and the provider will make sure that it installs solar panels that produce over the long-term, or they won’t make any money! So you don’t have to worry!

      Thanks for the question! Glad you’re going solar! You’re going to be happy that you did!

    1. Hello Matej,

      Thank you. SunPower 300 and 315 are not included on the chart above because the chart is of “30 of the most common” solar panels used. The size and cost of the SunPower 300 and 315, though they are very efficient, cause them to be used in solar installation projects much less commonly than the panels listed. That’s why I have included a link to the 40 Most Efficient Panels available which includes both mentioned. Good question!

  6. What does anyone know about Topsun solar panels ?? Are they reliabale ?? They have been offered by a local company in Oz but I can’t seem to find out anything on them from other suppliers. They talk about a cell efficiency of about 18% for cells in their 400W panels.

  7. Where are panels from First Solar? They have proven efficiencies of over 17% and low cost. Are they not available to residential customers?

    1. Brad,

      Good questions. The charts above show panels of 200 W ratings, and common panels used in the 200 W rating range. First Solar produces thin-film solar panels with the highest panel rating of 87.5 Watts, which is why you don’t see them in the charts above.

      Because First Solar uses thin-film technology, their efficiencies are relatively low compared to standard pv modules. You’re right though, their cost is low as well. The 17% efficiency that you reference was only achieved in July 2011 in a lab. Unfortunately, First Solar currently does not offer modules of this efficiency on the market yet.

      First Solar modules are available for residential installations, though they tend to be used much more widely on installations of 10 MW and higher (which are usually commercial installations).

      You can compare First Solar efficiencies on the solar comparison table. Simply type ‘First Solar’ in the Search bar.

      Yours in solar,
      SRoeCo Solar

  8. Hmm…

    Thanks for the article, but I’m a bit confused…

    For example, you wrote:
    “But efficiency may not be the most important factor. I would argue that the two most important factors in choosing the best solar panels are 1) the annual kWh production (the expected output) and 2) the price.”

    “PTC= PVUSA Testing Conditions (realistic test conditions)”

    So, if I understand the above correctly, assuming the realistic test conditions are, in fact realistic, doesn’t that mean that the most efficient panels (measured under PTC conditions) will produce the highest annual kWh production (have the highest expected output)?

    You also wrote:
    “Would you pay more for “more efficient” panels, if I told you I could get you a less expensive system that outputs more, fits on your property and lasts just as long?”

    While of course, I’d opt for the less expensive system that outputs more (yet is somehow *less* efficient??) I’m confused as to how a less efficient system (measured under PTC) could output more…

    Thanks for any insight you can offer; I’m fairly new to all this.


  9. Thank you for the article. I recently attended a seminar for Solagex and was impressed. Thay use Canadian Solar-CSP-230P panels and A SMA America-SB5000US(240v) Inverter. Ithink I understand about the panels but you havent discussed what part (if any) the inverter plays in the efficiency of the system. And can you please also include a response as to the repudability of Solagex. Thank you

    1. Hello Martini,

      You’re right, inverters play a role in the overall efficiency of a solar pv system. I’ll work on an article and maybe even a comparison for you soon. As for Solagex, I’m sorry, but I know less about them than you, so I can’t comment on their reputability. If you’d like me to look over any quotes you’ve received, I’d be more than happy. You can use the contact us page.

      I also highly recommend to everyone to get multiple price quotes from different installation companies. Comparison shopping is good for everyone.

  10. Hi,

    Thank you for the good article.

    I leave in west Africa where the temperature is very high and the sun very bright. I would appreciate if you can recommend panels that have high efficiency at high temperatures and are rugged.

    Thank you,

    1. Hello Rudman,
      No problem. All solar crystalline pv modules are rugged enough to withstand extreme weather conditions. You can find highly efficient panels at higher temperatures by looking at panels with ‘Power Temp Coefficients’ closer to zero (0).

      1. Go to the comparison table.
      2. Click on the ‘Power Temp Coef.’ link. This will display that column in the table.
      3. Now click on that column title in the table. This will sort the column, putting the panels with the best ‘temperature efficiency’ at the top.
      4. Lastly, in the Search bar in the table type a number like ’200′, or ’210′, or ’220′. These are common panel ratings of solar panels.

      Now you can easily see which panels have high efficiency at high temperatures!

  11. thanks for the info. i recently attended a talk by a local installer that offers two brands of modules as options. i can’t remember the lower cost/less efficient per size brand, but he claimed that the more expensive, smaller, more efficient panels manufactured by schott (a german company that manufactures the panels in new mexico) were 20% efficient. schott has lots of specs on their website, but i don’t know what all the tech talk means and i don’t see the “20% efficient” claim there. do you know anything about these being 20% efficient? from what i can read of the independent testing they seem to be of very high quality. thanks!

    1. Hello George,
      You’re right, the installer was exaggerating the efficiency, or made the mistake of simplifying the numbers instead of simplifying his explanation. Glad you’ve done the independent research on your own. Schott does make high quality panels. Don’t worry too much about efficiency. The best thing to do is to ask for a free solar estimate for your specific situation (ie. location, building, electricity usage) from 2 or 3 different solar installers. THEN, compare the specifics of their offers. Feel free to contact me after you’ve received the quotes if you’d like help comparing offers. Glad you’re considering going solar!

  12. Sanyo has 21% efficient panels in Europe, they recently were approved for the U.K. too.
    And for the DIY guys and gals, there are several 17% efficient solar cells (I didn’t check for panels) on the Chinese portal, for about $1/W.

  13. hi,

    how can solar cells loss power to module.
    for example cells have 16.7% efficiency then after install to module it will be around 16%
    it that due to EVA or glass.
    please explain detail to me.

    sorry for my bad english

    1. John – The manufacturing of solar cells is a highly intricate process that results in solar cells produced with varying efficiencies despite coming through the same processing facility. The efficiency of a panel (or solar module) is a collection of many of these individual cells wired together. The wiring, connection, and combination of the cells will result in a model efficiency being less than the laboratory-produced efficiency of single cells.

  14. Hi have you done a comparison on AC solar panels with Microinverter vs Solar panels with a traditional inverter, and how do the System stack against each other. I am trying to go solar but i don’t which system to choose. I don’t want to invest on a traditional system with one inverter, if the solar market is moving to AC solar panels and microinverters.

    1. Fernando – No, we don’t yet have data comparing microinverter output vs standard inverter output. The usage of microinverters on solar panels is still relatively new, so we don’t have any reliable comparison data. Microinverters can generally be expected to produce slightly more output compared to standard (big box) inverters, but if they produce enough to make up for the extra cost depends on individual scenarios. Ask your installer(s) to give you a price estimate for both options and then you can compare the cost and expected output differences. Feel free to contact me if you’d like help comparing installer estimates.

  15. This is a very helpful website! Keep up the great work! I am a college student considering fitting my parents home with solar panels and have been doing some research on them. Hopefully I can convince them to do so if I get some quality hypothetical results.

  16. Hello,
    Thanks for the useful information. I am currently researching if there any solar panels fitted with tracking system to detect the most sunshine available and position the solar panel accordingly to get the best energy output scenario? Is it efficient to use that system?

    1. Pavel,
      Solar tracking systems are calculated to track the Sun based on it’s position in the sky during specific times of the day and days of the year. They are automatically designed to maximize output in that regard. Yes, you will gain efficiency using this type of system as long as the output difference is greater than the energy needed to move the panels. Trackers also add cost ($) to the overall system.

  17. Hi SRoeCo Solar
    Firstly, many thanks for sharing great source of information and conducting very absorbing discussions from both you and readers. Fantastic job indeed!
    I am about to start business, providing telecom and computing solutions for government and corporate sectors completely based on standalone UPS power from Solar Photovoltaic panels. I want to use DC power supply only in these systems where possible. Grateful, if you can advise on what is the best way to start accurately calculating Solar Panel and Battery needs (including over space and weight needs as this is going to be mobile solution). I have browse through many sites but none provides complete picture.

    Warm Regards / Arvind

    1. Arvind,
      Glad you appreciate the site. It’s my pleasure. Designing a battery DC solar system from scratch is no simple task. I’m sorry that I can’t advise you in this area. Two resources to check are Backwoods Home and SolarPro Magazine. You’ve got an interesting idea! If you hope to succeed, don’t give up. The world needs more sustainable energy entrepreneurs.

  18. Hi,

    I have just had a 4.5kW system installed by a professional company in Australia. The system uses 20-Suntech 225W panels and a 4.2kW Aurora Inverter.

    We have not seen a Peak Power reading greater than 3.1 kW on the inverter meter since installation one month ago. This is despite perfect conditions with with clear skies and the sun directly overhead. Ambient temperature was noted to be low, 20-25 degrees when the observations were made at mid-day. The panels are inclined at 30 degrees and face directly north (optimum orientation conditions). Our lattitude is approximately 37 degrees south and there is no shading on the panels.

    My instincts tell me that there is a problem with the system due to the low peak power readings seen. Given that power generation conditions are excellent, what percentage of the advertised 4.5kW should I be seeing at the inverter meter.

    Suntech guarantee their panels to have 95% of rated output in the initial years of their life. Is the lower rated 4.2kW inverter the problem? For your information, I have compared readings on the same days with a neighbour who has a ten year old system. He reports 85% power generation of his system’s rating

    Your advice is appreciated.


    1. Hello Paul,

      I believe your instincts are correct. There seems to be a problem with the system. You should contact your installer, inform them exactly what you’ve written here: mainly that the peak ratings have not been higher than 3.1 kW for the first month. This is about 69% of the 4.5 kW rating, when you should be maxing a lot closer to 95% peak power readings (or ~4.2 kW).

      You can check other solar pv output data at Here is an example 4.464 kW system with Suntech panels for your comparison.

      Thank you for describing your situation so well. Please, let us know the solution to your issue when it is found. Though most pv systems should work without a hitch from the start, your situation could be helpful to future pv system owners.

      Yours in solar,

  19. Hi All,

    Its interesting to compare module efficiency, but in most cases, it’s little more than an academic exercise, as long as you are comparing the PTC or CEC ratings, and not relying on the STC ratings that look more favorable.

    There are only 2 conditions where the module efficiency matters for residential installations:

    1. Limited mounting area requires a more expensive, higher efficiency module to allow the desired array to “fit” into the available space. In other words, you need a 5 kW array, and only 4.6 kW would fit with the lower efficiency modules, so you decide to purchase the more expensive option to reach the 5 kW goal.

    2. If there is a big difference between the STC and the PTC, you should figure out expected production, and compare price quotes based on that. Solar modules and even installed systems are sold by the Watt, just as chicken is sold by the pound (or kg). Usually the STC is the figure used to price a system at, say, $5.50/watt. Comparing the cost to the more realistic PTC or CEC numbers would give a better representation of which offer was the best value.

    There is no sense in a potential solar customer waiting until the efficiency reaches some particular level — a 4 kW system will make the same amount of power at 35% efficiency as at 15% — it just takes up less room to do the same work.

    Clear skies,

    Brad Vietje
    Green Works Solar Store
    Groton & St. Johnsbury, VT

  20. Hey Guys, I keep hearing about efficiency going up, but I don’t seem to ever see it happening. I fully expect the multijunction cells to get here eventually, but I also expect them to be expensive. I keep expecting the real specs like $/watt and $/area to go down, and even if the cells are more expensive the assembly process costs must still be a large chunk of the price. Given that the global installed volume is ‘charging’ :-) up fast, I would expect the installed price/watt to keep coming down. When is all of this going to become practical, after the subsidies end?

  21. this is wealth of information! thank you,

    I have some questions about the longevity of solar systems. it appears that most systems are guaranteed for about 20 – 25 years. but what happens after that? would you have to purchase a whole new system?

    what type of maintenance is necessary to maintain the system?

    1. Thanks Joey. Actually, nothing happens. The panels keep producing energy even after 25 years. It’s possible that the panels could continue producing energy after 50 years (albeit likely at 60-80% of what it produced in Year 1). So, no, you won’t have to purchase a whole new system. You would likely have to replace the inverter every 10-15 years, but not the panels.

      Maintenance is typically keeping the panels clear of too much debris (dust, dirt, leaves, etc). Depending on where you live, simply hosing the panels down with water every few months is sufficient. Here’s an article on 1BOG about solar monitoring and maintenance.

    1. Hello Randers,

      Thanks for the comment. Yes, my list is up-to-date as of 2/16/2012. I’d like for you (and all others) to be wary of news articles claiming certain panels to be ‘the best modules’ of all, or the ‘most efficient’ in an ‘industry leading test’.

      The article you referenced is published on REC’s website stating that REC has the best performance panels in 2011. If you look a little deeper, you will notice that the German research lab conducting the test comparing panels, did not include the data for modules from SunPower, Sanyo, Mitsubishi, Yingli and several other solar companies. The lab actually mentions in the full write-up that the measurement tools were too slow to correctly measure “certain high-performance modules”, specifically SunPower and Sanyo.


      Bislang war es den Modulmessgeräten nicht möglich, die Kennlinie bestimmter Hochleistungsmodule sekündlich zu vermessen – das Messgerät war schlicht zu schnell für diese Module, die auf Änderungen beim Abfahren der Strom-/Spannungskurve aufgrund ihrer hohen parasitären Kapazität eher träge reagieren. Davon betroffen waren vor allem die Produkte der Sunpower Corp. sowie der Sanyo Electric Co. Ltd.

      English (from Google Translate):

      Until now the module instrumentation is not possible to measure the characteristic of certain high-performance modules every second – the meter was simply too fast for those modules that respond to changes made ​​current during shutdown due to their high parasitic capacitance rather sluggish. This affected mainly the products of Sunpower Corp.. and Sanyo Electric Co. Ltd.

      Full write-up reference:

      Thank you for sharing. Things can get muddy while researching solar. This is precisely why I run this website.

      Yours in solar,
      SRoeCo Solar

  22. Great website and pretty easy to navigate. I provide solar solutions in Oz and your site will come in handy. 2 quaetions though:

    1. Is it possible to download all the info for in house review only (not for any publication)?

    2. Why don’t you add a column for panel type – whether mono, poly, thin etc so that comparison can be done simpler on apples and apples?

    Big fan of your work!!


  23. Hi, I’m planning a solar system on my sailboat. Due to limited space constraints, the efficiency of the panels I am considering are a very important factor. Thanks for the great information on this site, especially the comparison table!


  24. does anyone have and idea about the best roofing material to use to keep the heat away from the panels. i know that at least 3 to 4 inches is advised to allow air circulation. but from what i’ve seen no one has addressed roofing material the will not reflect heat towards the panels thus reducing their effiecenty

  25. Hi.

    What do you know about Suntellite 200W PV panels? I think they claim to have an efficiency of 14.7% (cell) and 16.7% (module), where do they sit on the ratings chart as I can’t really find much on them (confused!!)? I’ve been offered a reasonable deal on them, but I’m a bit in the dark by the choice.

    Many thanks in advance for any advice.

  26. I have a solar system installed a few weeks ago. It includes a monitoring service, through which I can see each panel’s output in real time. If one panel were to die completely, it would be easy to determine. But how can I tell if the amount of power they are producing is in line with the manufacturer’s warranty? For all I know, some may have more modest production flaws that means they are underperforming, or they may begin to underperform 10 years from now while still providing some level of output. This seems to me to be pretty tricky, given the variability that occurs with changes in season and degree of cloud cover.

  27. Great charts you got there comparing whats the best PV panels. But how about building your own solar panels from pv cells? I heard that you get more bang for you buck from them.
    One thing I missed on those charts was the estimated wattage per hour on full sun. That would be a great statistic to add on your future pv comparison charts, I’d love to see some numbers on this factor.

  28. Hi

    Thanks for sharing all the information on the solar panels and keeping the same current. I am from southern part of India where we have 9 months of clear sun with 28-34 deg.c temperature and 3 months of rain. We were planning to enter the solar farm culture here as the Govt. started giving lot of subsidies to promote alternate energy generation. Also we find the cost of ownership reducing and grid connectivity increasing.

    Hope very soon high efficiency panels will be available soon. As of now we are making our own inverters and just sourcing the panels. We do complete turn key installation and maintenance of the whole system.

    Thank you for the helpful information. Keep it up.
    Best Regards

  29. Enjoyed reading all the various responses. I’ve read recently that Sharp is producing a panel they refer to as Sun Snap with a 36.9 efficientcy. Apparently they have there own individual inverters which allow for the system to be expanded over time. I am contemplating installing a system and this seems very interesting. Any imput would be welcomed. Thank You! Jim L

  30. Great information, and some thoughtful responses to the questions you’ve received (love your Feb 15th response, showing how REC conveniently excluded key competitors from their analysis!)

    My question is how you treat density as different from module efficiency. As far as I’m concerned, they’re the same thing. One is percent of the energy hitting the module; the other is that same value in watts. Yet you seem to treat them as different information, and your tables support your position.

    I’ve only thought about this for a minute, but it seems that the only way that the density vs efficiency ranking could change the ranking of the modules is if one column was based on STC conditions, and the other on PTC test conditions.

    Am I missing something?

    1. Bill, Thanks for the compliments. You are absolutely right. Density is based on PTC (real-world conditions) and standard efficiency ratings use STC (laboratory) conditions.

      I like your site It has a lot of useful information for California residents in the PG&E area.

  31. I don’t see solarworld [255] panels on any of your charts, are they good? This is a USA company based in Oregon with an outlet in California.

  32. I am in Queensland, Australia. I have PV Panels on my galvanised iron roof. The panels were supplied & fitted by Eco-Kinetics a large Australia wide company. The panels I believe are Shenglong PV-Tech (LONG ENERGY). It is a 2KW system. When the panels were 2 1/2 years of age we noticed that they have gone a brown colour (we believe it to be EVA browning) and where the water off them drips on to the roof at the lowest points it is rusting the galvanised roof.I also believe that the panels are putting out less energy. As I can not get any sense from anyone here that this is the cause of the said problem I was wondering if you could offer any comments.

    1. In regards to your browning solar modules, it is highly likely that the panels have degraded due to improper manufacturing (or installation/handling). Here is a link to a NREL (National Renewable Energy Laboratory) presentation on module degradation including photos of modules with EVA browning. If your panels look similar, this is likely the case.

      If the case, your modules should be covered by their manufacturer’s warranty of output performance. The warranty documents for Shenglong can be found here. Contact your installer and ask them about the process necessary to replace your solar panels under the manufacturer’s warranty. They should help you out and replace your degraded panels with no problem.

      Let me know if you have any further questions or problems. I hope that this issue is solved quickly and easily.

  33. Further to your correspondence 18/6/2012. EVA browning as shown in the NREL Link is the same as the panels on our home. Under the lowest parts of our panels where moisture/rain drips off the panels there are corrosion/rust spots on the hot dipped galvanised roofing. Do you think this could be caused by a chemical reaction of sorts from the EVA browning? I have just been on the roof and found one panel has corrosion on the inside in the last month. (I am sending photos via your E-Mail). Eco-Kinetics will not give claim-have said the browning will not do any harm, so have sent E-Mail to Long Energy-now awaiting answer. We would very much appreciate your opinion.

    1. I received your photos via email and have responded in full. Summary: From my research, it is unclear if the EVA browning has contributed to the rusting of the roof. However, it appears clear that the installation of the solar panels without a rain gutter or other drainage system to collect the rain runoff and redirect it away from the metal roof has increased the natural rate of corrosion of your roof in the lowest point areas where the water has collected and dripped onto the roof.

      I would recommend considering the installation of such a rain water runoff collection system to prevent further corrosion in these areas.

      In regards to Shenlong Energy (Long Energy), they will likely need data showing that each panel is producing below the guaranteed output performance in order to initiate the warranty claim. Again, I hope that your concerns are resolved in a timely manner and with as little stress as possible.

  34. Hi,
    Fantastic site and a million thanks for the effort which must be daunting.

    I live in a generally overcast and cold (appr. 0C) Winter months area. What would be the best choice of PV cells and invertors for me to use? Is there one that is know to have been designed specifically for (or operate at higher efficiency in)low light/shaded/overcast areas?

    Thanks again,

    1. Hi Steve,
      Thanks for the compliment. Glad you appreciate the site. The good news is that solar panels (and all electronic devices actually) work even MORE efficiently in colder temperatures. Notoriously cloudy places like San Francisco and Germany have thriving solar industries despite their many cloudy days. (Germany produces the most solar power in the world). And these places use all makes and models of solar panels. There are no ‘special’ modules you need to worry about. Hope this helps!

  35. Living near the beach and getting quite a bit of morning fog in the summer, how do the systems compare in non-optimal conditions?

  36. Hi,
    On your last post dated july 18th 2012 (#71) the one with the link “germany produces the most solar power” do you have a more current link as that link refers to 2009? and i read that they are now producing 22 gigawatts in 2012, germany that is. great site i like it very much, thank you for maintaining it.

    1. Hey William, Here’s a more recent reference about the top solar countries. USA has moved up to #4 and we’re close on the heels of Japan for the #3 spot. Hopefully we’ll keep the installation pace faster than Japan to surpass. It’s my pleasure maintaining this site. Thanks for the appreciation!

  37. HiShawn
    Thanks for your E-Mail 23/6/12. Unfortunately this saga is still ongoing. The Clean Energy Council(our peak Solar Industry body) has said there is a definite issue with the panels and recommend that the company from which the system was purchased be contacted and asked to replace the panels as they are turning into a possible hazard. Eco-Kinetics is supposed to be coming to our area in August and will inspect the panels when they are here, but it is now the 8th and we have heard nothing from them-hope it eventuates. As for the rust it appears they will only wire brush the rust and paint the affected areas. At least we may finally get someone to have a look at it, as neither Eco-Kinetics or the Clean Energy Council seem to think it was worth looking at. As for the E-Mails we sent to Long Energy they never even had the decency to say they had received them-we know they would have millions of customers, but how long does it take to send an E-Mail(unlike you!!) Sorry this update is a little late-still tearing our hair out-will keep you posted.
    Much thanks

  38. hello….can some one tell me what are the best working conditions(most efficient rather) for a photovoltaic cell.please answer in terms of temperature,altitude etc..

  39. Hi just wondering, when it says that a 200 watt panel is 17.24% efficient, does this mean the panel is only producing 34.48 watts?

    Or the panel is manufactured to produce 1000 watts but is only 17.24% efficient whihch = 172.4 watts but they round it up to 200 watts?

    Also, is their way to find out at what % does the panel increase or decrease at certain temperatures?


    -200watt panel @ 20c = 17%
    -200watt panel @ 21c = 16%
    -200watt panel @ 10c=27%

    at what % does the panels efficiency increase at what degree?

    Does this make sense?

    Thank you!

  40. We stumbled over here coming from a different web address and thought I should check things out. I like what I see so now i am following you. Look forward to exploring your web page again.

  41. I’ve recently been looking at solar systems and I’me very disappointed that the carpet baggers are still in the market. I asked for quotes for a 6 kW system only to receive quotes for 6 kW worth of panels but 5 kW and even 4.8 kW inverters.
    Yes 6 kW (nominal) of panels will not produce 6 kW due to location, amount of sunlight, mounting angles etc. but you install more panles to at least take you to producing close to 6 kW at optimum local conditions.

  42. I have installed 5kwP Solar power system but I have faced problem about the Solar Charge Controller, I do not have the suitable Charge controller can advise me the best Charge controller I use.


  43. I received a quote from SunPower for SunPower E20/327 solar panels. I couldn’t find these panels listed. Also, is it better to lease or buy the systems outright?

  44. I will be biulding an off grid home this summer. my first requirement is for temp power for tools, that can later be incorporated into the home system. let’s talk, my phone #is (612)396-1442. my name is larry parks

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