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April 23, 2014  |  Login
Buying Solar Panels
By Dan Chiras
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Buying a Solar Electric System: Panels and Inverters

When buying PV (Photovoltaic) modules, you’ll find that you have quite a lot of options; over a half dozen manufacturers produce several different sizes of modules. Fortunately, they’re all pretty good, so it is hard to go wrong.

Given this, what criteria do you use to select a PV module?

If you are working with a local installer, he or she may have a favorite company he or she has had good luck with. In fact, most local installers are distributors for one or two of the major PV manufacturers. Call several local suppliers to see what each one offers.

If you want more options and want to save some money, you can contact a reputable online source. Experienced and knowledgeable sales people may be able to give you sound advice on which panels will work best for you. Be sure to ask for sale items, too. You can often obtain some amazing deals this way. Also, be sure to ask if their companies offer any solar kits. Solar kits are complete packages that include the modules, racks, inverters, controllers, and everything else you’ll need. Kits usually include whatever type of module the supplier can order in bulk at a deep discount, which they pass on to you.

When it comes to studying your options, I found ETA Engineering’s website ( ) very useful. They provide information on modules from six different manufacturers (although there are a few important manufacturers like BP Solar missing from the list). ETA’s descriptions of the various PV modules that they sell include tables that list key information you need to know when purchasing one, including power output, maximum power voltage, maximum power current, cell efficiency, and physical dimensions. You can use this information to compare modules from different manufacturers. (I’ll fill you in on this shortly.)

One criterion many solar buyers use when comparing modules from different manufacturers is the cost per watt. To determine this, simply divide the cost of a module by its maximum power output. The maximum power output is the maximum wattage under standard test conditions (1,000 watts per square meter of irradiance at 25°C or 77°F cell temperature). Sharp’s 165-watt panel, for instance, produces 165 watts under standard test conditions and costs $639 through ETA at this writing (December, 2004).The cost per watt is $3.87. Kyocera’s 125-watt PV module sells for $489 or about $3.91 per watt. These are good prices, by the way, although you can sometimes purchase PV modules on the Internet for as low as $2.08 per peak watt— so shop around!

While you’re shopping around, be sure to check out the manufacturers’ warranties. The ETA site lists this for the modules they sell. more



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