Watt Really Matters: Bigger is Not Always Better

Posted on December 8th, 2011 by

Just like you wouldn’t put a Porsche engine in your Beetle or dare to run your lawn mower on a fierce V8-engine, there is an optimal fit for everything. Equally, in the solar energy photovoltaic industry it is about much more than ‘size’ alone. One might think that the higher the wattage of a module is, the more bang it will give you for your bucks—but when it comes to system design, this isn’t always true. The perfect PV-system is a finely orchestrated symphony of watts, square feet, and efficiency.

The basics of this sustainable energy masterpiece are you and the module; to be more specific- the expectations you have for your PV-array and the type of panels that will help you achieve this goal. Aside from huge open solar farms, the average PV-application has to perform within a limited amount of space available. Ideal prerequisites for a solar system are, of course, a south-facing roof or area for a ground-mount that will allow for the magical optimal tilt or pitch without any shading. So you identified your “sunny side” (or close to it)—what’s next? Instinct might tell us to put as many high wattage modules on it as possible, but this is exactly where the engineering rubber hits the road.

Most consumers are under the impression that the higher the wattage of the module they purchase, the more it will yield them and maximize their profits. Let’s take a closer look at this theory. Today the majority of modules range from 180W to 240W but the higher the wattage, the bigger the actual size of the module. Let’s say your garden shed is the ideal spot to be solarized and you have the option of either fitting 240W modules on its 210 sq ft roof or 190W panels—is the higher wattage necessarily better? No. You’ll get more efficiency and power out of the 190s. This is actually not a magic trick but straightforward math.

Panel dimensions being as they are, the 210 sq ft roof space will either accommodate ten of the bigger 240W panels or (drum roll, please) 15 of the smaller 190W panels. Therefore, your solar-math should always include the wattage you get per square foot, in this case: roughly 2.4 kW with the bigger size, higher wattage modules or 2.85 kW with the smaller and lower wattage ones. Granted, this is only a small-scale example but it will add up tremendously over time, system size, and a few other factors a solar buyer should take into consideration.

There are a number of good quality panels out there and their efficiencies are ever improving. Solar Customers, too, can do their part to maximize their gain from this investment. Simple and easy: In order to allow your system to operate at maximum efficiency, your modules should be cleaned at least annually. It completely suffices to simply hose them down with water (never use any abrasives or chemicals on your modules as they could damage the glass, its silicone seal, or cables). Also take into consideration to challenge your installer to offer you the best the market has to offer. It is not just about size, but effectively what you get out of it. Demand high performance modules with positive watt tolerances only, meaning (in the case of a 190 W panel) you will actually get at least 190 W or more out of your panel, never a negative tolerance. This truly is the quintessence of having your pie and eating it too: Smaller size with higher wattages and no losses—it simply doesn’t get any better than that!

Know that your installer will save additional time by selecting a sturdy, easy to install mounting system, like the newly introduced smart snap-and-slide technologies that have just hit the market. Again, quality and product warranty are paramount as the best PV-system is only as good as its weakest link.  And then, lean back and let the sun shine. While you reduce your carbon footprint your return on investment keeps growing—and you might be able to get that sports car after all, e-version, of course.

Written by Sylvia Minton, who heads the Public Affairs Chair of the Georgia Solar Energy Association. A long time journalist and communications specialist, the Sr. VP of Corporate Affairs for MAGE SOLAR, a complete solar PV systems & components provider, is a member of the board of directors of the MAGE SOLAR ACADEMY in Dublin, GA, USA. MAGE SOLAR ACADEMY, located at the corporate campus of MAGE SOLAR USA in Dublin, GA, is a premier educational arena for professionals of all levels and occupations in the expanding PV-market. A subsidiary of the international MAGE GROUP, the academy boasts over 10,000 sq ft of state-of-the-art educational technology, indoor and outdoor training and simulation areas.


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