Choosing PV Modules: Page 2 of 3

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Inside this Article

Solar panels on a rooftop
Solar panels on a rooftop.
Garage roof is good location for solar panels
This large, south-facing garage roof has access to a wide-open solar window—the perfect location for a future PV array.
Module from Helios Solar Works
This 420 W module from Helios Solar Works is manufactured in Milwaukee, Wisconsin, and has a +3/0 power tolerance.
SunPower module
This SunPower 435 W module is 20.1% efficient. High-efficiency modules allow a higher-capacity array to fit within a limited area.
Peak Energy module from REC
This Peak Energy module from REC has a PTC-to-STC ratio of 0.91.
SunPower Signature black solar modules
Using high-efficiency modules can reduce the mounting space required. This 12 kW array uses SunPower Signature black solar modules for aesthetics.
Silicon Energy Installation
In some programs, purchasing components made in-state qualifies the system for larger incentives.
Lumos Solar frameless modules
An awning that uses Lumos Solar frameless modules with clear back sheets allows light to filter through.
Trina Solar modules
Zep Solar-compatible modules from Trina Solar have grooved frames to accommodate hardware for rail-less mounting.
Upsolar modules
Zep Solar-compatible modules from Upsolar have grooved frames to accommodate hardware for rail-less mounting.
Jinko Solar module
This Jinko Solar 245 W module has 10-year materials and 25-year linear power warranties.
PV modules can be both a science and an art
Every residential installation is unique—and selecting PV modules can be both a science and an art, where production, budget, and aesthetic goals are balanced within a given space.
Solar panels on a rooftop
Garage roof is good location for solar panels
Module from Helios Solar Works
SunPower module
Peak Energy module from REC
SunPower Signature black solar modules
Silicon Energy Installation
Lumos Solar frameless modules
Trina Solar modules
Upsolar modules
Jinko Solar module
PV modules can be both a science and an art

Power density of a module is dependent on module efficiency and is given in watts per square foot. The greater the density, the more power the array can generate per square foot. But higher module efficiency also means more dollars per watt, so before you assume you need a high-efficiency module, check the amount of space you have compared to the total power you want (see the “Selecting Modules for My Garage” sizing example).

Module dimensions need to be considered, especially if you’re working with limited mounting space but trying to maximize array capacity. Often, you’ll have to compare layouts, including both portrait and landscape configurations, to find the appropriate array layout for a rooftop. When using a string inverter, layout options may need to consider the required number of modules in series (and the number of parallel strings) to make sure the array layout is compatible with the inverter’s input and output limitations.

PV manufacturer location can be an important factor. First, some production-based incentives, such as Washington state’s RE System Cost Recovery program, pay a higher per-kWh incentive for systems with locally manufactured equipment. Systems funded by the American Recovery and Reinvestment Act (ARRA) and installed on public buildings must use domestically manufactured modules (or foreign modules that use 100% domestic cells). The less distance a module has to travel to its ultimate destination, the less embodied energy that module has. Finally, many people want to support local manufacturing jobs over foreign jobs and imports. See “PV Manufacturer Profiles” sidebar for information on how to find manufacturers offering ARRA- and Buy American Act-compliant modules.

Module frames and back-sheets are important to mounting technique and aesthetics. Options include frameless modules, module frames with mounting grooves for rail-less mounting, modules that allow some light to pass through (popular for awning systems), and dark back-sheets (black), which provide a more uniform look within the array.

PV wire leads are required for ungrounded arrays. Transformerless inverters are becoming increasingly popular because of increased inverter efficiency and enhanced safety (see “Ungrounded PV Systems” in HP150). However, they do require the array to be ungrounded, and the modules selected must have “PV-wire” cables for these installations. (PV-wire has specific benefits over standard USE-2 conductors including thicker insulation, higher voltage ratings, better UV resistance and flexibility in extreme cold.)

Warranty is important, and while most PV manufacturers offer 25-year power output warranties, material warranties can range from two to 10 years. A warranty is only helpful if the company offering it sticks around to service a future claim. With the PV manufacturing industry undergoing so much change right now, and many companies merging or exiting the market, some manufacturers are offering noncancellable warranties serviced by third-party insurance companies.

Cost is always a factor and budget can dictate the array you ultimately purchase. Module pricing has been on a downward trend over the last few years. A brief online search shows many modules are available for $1.50 per W; some even below $1.

Online module shopping—to try get the cheapest deal—instead of buying from a local module supplier/installer has drawbacks. While the array may cost less up-front, you may be without support should problems arise. In certain areas, installing a grid-tied system without a licensed installer means forfeiting some incentives. While the modules table lists more than 900 modules, no matter whether you buy online or through your local PV installer, available options will be limited to those modules currently offered by that supplier.

Comments (4)

Justine Sanchez's picture

Hi Stephanie,
Thanks for posting your comment about Colored Solar modules. Folks can check out their specs and compare to other modules on the list if you go to: http://www.homepower.com/web-xtras
and click on "2012-2013 PV Modules Buyer's Guide"
Best,
Justine
Home Power Magazine

stephanieb's picture

These factors are all important when comparing apples to apples, but introduce an aesthetic US made pv panel like from Colored Solar into the equation. 1) Do we need to put a imported product on every roof in America? 2) Does solar have to detract from traditional American architecture? 3) Homeowners are proud of their home's look and appearance and have to only choose black to outfit their home with 4) Colored modules perform better, than black panels

Michael Jacobs's picture

I really enjoyed the article. I shared it with my students. We were discussing the selection of pv cells for student design projects. The article explained the criteria used for making their pv cell selection which was helpful to the class in their student design project. Worked very well with a real world experience. Love this magazine. I have learned so very much from the articles. People know me by the magazine i carry with me at all times. Thanks so much!!!

Michael Welch's picture

Hi Michael. Thanks for the kind words, and we're glad you and your students are finding good value in the magazine.

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