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Choosing the Best Solar Panels or Photovoltaic Modules

Updated on September 7, 2012

What is a Photovoltaic Module?

There has, in recent years, been a huge movement worldwide, to harness renewable energy for both residential and commercial use.  Energy from from sun, wind and water has been used in making mans work easier since man was first created.  Let us hope that we are finally realizing that sucking the remains of decomposed prehistoric life from another earth age and burning it may not be such a good idea after all.  The sun has warmed the planet since the beginning and contains photons that have provided light as well.  These photons can now be harvested and converted into electricity by semi conductor cells of silicon.  These cells, when placed in groups behind a glass panel, can produce electricity in amounts high enough to offset a substantial part of the cost of buying power when these modules, or solar panels as they are commonly known, are grouped together in an array on a south facing roof or in a field.

There are two basic types of these systems in use today, commonly referred to as on grid and off grid. The names mean exactly what they say. An on grid system produces electricity as DC (direct current) that is converted into AC (alternating current) and feeds it into the meter to the utility power grid, causing a reverse of power at certain times, and actually making the electric meter run backwards, crediting the user for the amount produced.  The ability to flow in either direction is a characteristic of AC power.  On grid is the most common solar energy producer used today.  The efficiency of this system can be increased by daytime light havesting and geotherm heating and cooling. Off grid is an independent stand alone system that powers one or more buildings or machinery. These generally require large storage cells, or a UPS, (uniterrupted power supply), to keep the flow to the power inverter during non daylight hours of operation. These systems are far less common however the success of the MIT liquid battery could make this more plausible. Today we are all becoming more familiar with the rectangular arrays on the roofs of certain homes and businesses characterizing the on and off grid systems.

There are three basic types of photovoltaic modules common, and in use, today.  Mono crystalline, poly crystalline and amorphic.  All three are forms of silicone that is grown as ingots and sliced into thin wafers.  The cost of this production is high and supply and demand makes the cost of the modules fluctuate.  Unlike an electric flouoescent lamp or light bulb that costs a basic retail price, more or less, for its wattage, solar panels are priced at a per watt cost with frequent market fluctuations like any commodity.

Mono crystalline or single crystal silicone is the most expensive to produce and also regarded, by most, as having the greatest efficiency.  It virtually never fails unless the wires that carry the current become corroded.  That is not an expensive fix.  These modules can have an expected lifetime performance of 35 years or more at 80% efficiency.

Poly crystalline or polysilicon is less expensive to produce and is regarded, by most in the industry, as slightly less efficient than Mono.  Its many rough edges between crystals cause difficulty in the electrical flow.  Poly crystalline panels still, generally, have a life expectancy of 25 years or more at 80% efficiency.

Amorphic panels have a thin film spread over a backing and contain a large number of tiny crystals that deter the flow of electricity and are subject to greater degradation over a period of time.  This is a very inexpensive option but not for an extended period,

Regardless of the type of module utilized they all must rely on inverters to transpose the DC current into AC, and a monitoring system to continuously check the operation of the system for output fluctuations that could indicate a problem.  The inverters can convert inividual panels as microinverters, or groups as central inverters.


Who Needs It?

If you have an overwhelmingly expensive KW rate for your electric power,or live in a state where the sun shines most of the time like New Mexico, and your state has put a demand on the power providers to produce a certain percentage of their energy from renewable sources and there is a state or power company rebate, solar energy is not something you should ignore. It is, in fact, a fast moving train that you should catch now before it pulls out. We can't all, of course live in New Jersey, Pennsylvania or California, where the incentives from the providers and the state government are high. However, despite the great rebate programs in those three states and others , they are not on the list of States that are considered the best choices in the US for solar enhancement.  Why?  Just because they offer rebates and incentives, in the form of SREC's. (Solar Renewable Energy Credits) that are tradable like stocks and sold at auction, there are other states that offer more, like daily hours of sunshine, or insolation as it is referred, low cost energy installation aside from a high KW cost and an offset of carbon emissions.  A state that depends on burning coal creates a huge carbon emission compared to a state that utilizes hydroelectric power.

So to answer my own question, in the subtitle of this article, I will tell you who needs it.  Anyone who is concerned with the depletion of natural resources on this planet, who is concerned about global warming due to emissions from power plants.  Anyone who has respect for the next generation, if not only the children that will inherit the planet, but also the species of animals and plants that are vanishing as I write.

It is not about how many years until you get a payback or getting green, which you eventually will receive anyway, it is about how much you will pay back and what kind of an environmental legacy you leave or giving green.

Choosing Solar Panels for your Home or Business.

Since the influx of world interest in the implementation of renewable energy systems, several countries have become deeply committed. Germany has led the way in the world for her utilization of solar power. China has become the worlds leader in the production of PV Modules and now the most desirable country to market renewable energy to, according to a recent report. 95 percent of all panels produced in the US, Canada and Europe have at least 49 percent of their components outsourced to China. Other European countries have grabbed the reigns and held on without Chinese dependency. REC, the Norwegian Company with offices in the USA, being one example. They have chosen Singapore for their newest manufacturing operation and are holding to the specs that gave them their reputation of quality. There are a couple of US manufacturers that are still in the homegrown only game today and will remain. These companies will benefit well from the new demand caused by the "Buy American" movement. There are dozens of other brands from factories around the world of greatly varying quality and pricing, and that is what makes choosing confusing, especially for the consumer. Add to that mix layer after layer of manufacturers, vendors, distributors and master distributors, reps and subreps, retailers and internet marketers all claiming to have the best product at the lowest cost. Some who have just entered the market and will exit just as quickly. Some that require purchasing a minimum of hundreds or even thousand of units. Multiply that times several hundred dollars each and that is an enormous investment. Others will sell a freight container to anyone at the lowest price FOB China. If one needs only to buy a dozen, or two, for his residential or commercial roof where does he go? The home center, the installer, an electrical supply house or the internet? The correct answer is the internet but not to buy right away but to study diligently. There are several very informative websites that will rate the various products. Forums from professional groups like LinkedIn and blogs are also good places to get information to help in the decision making process. Check the PTC rating of any product on this California Solar Site. This will measure the true wattage against the manufacturers published wattage. Look for a rating close in number when choosing a product. For example if you are interested in a 240 watt module the PTC rating should be very near that number. The efficiency rating is important also, determined by the square footage output. The efficiency is not all that you should take into consideration. The two most important factors are the annual KWh and the cost. Do not rule out a product just because of its country of origin either. Some products made offshore are of very good quality like Alex Solar which are made in China but are inexpensive and highly PTC rated. As mentioned earlier, many US and European made products have mostly Chinese components and some do not. It is up to you, the buyer, to become educated before making a decision. Ask about support in the future. Will the company still be there to honor that 30 year warranty in 25 years? What about that warranty? Who is offering it? You would not buy an appliance without a sound warranty. PV modules are no different. It is a big investment that you will, hopefully, only make once. One last very important issue, always ask in advance for a factory spec sheet on the product that contains all of the manufacturers specifications and ratings. If it can't be provided move on to another source and do not look back!


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    • profile image

      James 7 years ago

      Informative hub, it's great to use solar powers, thumbs up :)

    • aimbig profile image

      aimbig 7 years ago from San Diego, CA

      This is very useful information. Thanks for sharing..

    • frogpatch profile image

      frogpatch 7 years ago from Jersey Shore

      Thanks so much for adding your apparent years of engineering experience to my article. Your comment has enhanced it, to not only help the advanced consumer, but also the people, like myself, who are relatively new in the industry but have achieved their knowledge from closely related fields apart from renewable energy. Thanks for completing this!

    • profile image

      Putting4Par 7 years ago


      In addition to the excellent points you've made, there are a few other exercises that a consumer might want to undertake when selecting modules. A simple way to measure the relative efficiency of one module against another is to divide a module's PTC rating by it's nameplate or STC rating. For example, the Canadian Solar CS5P-235M 235W Monocrystalline Module would have a relative efficiency of (214.1/235) .91125 or 91.125%. Compare that to a Sharp ND-U230Q2 230W Polycrystalline Module at (207.4/230) .90174% or 90.174%. This formula gives the homeowner a way to compare apples to oranges, meaning they can compare modules of dissimilar wattage.

      Consumers should also ask for the spec sheet for the particular modules being quoted and take a look at the performance tolerance. The example 235W Canadian Solar module has a performance tolerance rating from -0% to +5 watts. That means you are guaranteed a module that will produce no less than the rated 235 watts and you could get modules that produce as much as 240 watts. The Sharp solar module mentioned above has a power tolerance from -5% to +10%. That means the output of these Sharp modules could be 5% less than the rated 230 watts (218.5 watts), or you might get modules that actually perform 10% better than the 230W rating (253.0 watts) . The later module looks overall like it could provide you with much more power. Sounds great on paper, right? Well maybe not so much. It is actually more desirable to have a very “tight” power tolerance. You've heard the adage about the weakest link in the chain, well the same applies here. Solar systems run most efficiently when all the modules in a system are similar in wattage. Having a great disparity among modules is detrimental to performance.

      Homeowners must remember too that module efficiency is great, but what really matters is how much you end up paying for the electricity that will be coming off your roof. If you've done your homework and have multiple bids, use this simple formula to find out your cost for electricity. Take the gross cost of your system and divide it by the AC system size (not the DC system size). So, if the gross cost of the system is $28,592.00 and the system is 5.24 KW AC (5,240 watts), $28,592/5,240 watts = $5.47 per watt or $5,456.49 per KW AC. You may have a quote from solar company that is using modules that may not be the highest efficiency, but they may be giving you a great deal. Remember, efficiency has nothing to do with the overall quality of a module.

      Lastly, who you select to do the job is probably even more important than the hardware you select. The solar industry has become very reminiscent of the dot com bust. There is a tremendous influx of new installers trying to get rich in this “gold rush”, so buyer beware. I spoke with the sales manager of a new solar company who was very proud of the fact that all his sales personnel were former car salespeople! Check references very closely.

    • solar power home profile image

      solar power home 7 years ago from UK

      Solar power is a step in the right direction.In the UK the goverment now lets home owners with PV solar panels claim a tax free income for each Kw they produce.

    • frogpatch profile image

      frogpatch 7 years ago from Jersey Shore

      You are correct. Here is a site the lists the PTC ratings. It shows the actual output compared to the published output after test conditions were applied.

    • profile image

      EngineerPhil 7 years ago


      Very nice overview of PV technologies. I was puzzled though by your reference to an 80% efficiency for PV after 35 years. Do you mean to say that you can expect the modules to degrade by 20% over that period of time?


    • frogpatch profile image

      frogpatch 7 years ago from Jersey Shore


      Thanks for your comments. I sent you an email to the hotmail address on your website. I am a Senior Account Manager for a Solar/Wind Manufacturer and may be able to help you.

    • profile image

      Eliseo  7 years ago

      Thanks for your feedback Frogpath. As you well say the problem is still the price and quality of cells. The same is the difference between monocristlino and polycrystalline seems to continue fighting. Thanks again, I expect prices of them to be more transparent.

      Frog you can help me with a list of stores or companies that sell: solar cells, inverters and controllers. around the world. My subscriptor en my site in latinoamética want to make your own solar panel at home. May you mail any of them or the main like eBay en USA...but in europ, spain. Please help to me. MARRY CHRISTMAS..!

      Thanks again

    • frogpatch profile image

      frogpatch 7 years ago from Jersey Shore

      Thanks! Very true. There are no moving parts so it becomes harder to test the products against degradation and depreciation. You can put the best components into a product and cut one corner and weather and dirt become a bigger issue over time. The PTC ratings on the link above (Solar Site) in the article are a good indicator.

    • profile image 7 years ago

      Nice hub and great information. There are plenty pf pv modules available in the market and choosing one is a difficult task because the efficiency will depend on the quality of the device.

    • frogpatch profile image

      frogpatch 7 years ago from Jersey Shore

      Thanks for your kind words. I really appreciate them!

    • profile image

      adair_francesca 7 years ago

      Nice hub about solar panels especially pv modules.


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