The PV Module Index shows two high-achieving solar module brands for reliability, performance, and quality

PV module index

Solar industry success is only possible when solar installers, EPCs and developers procure reliable, high quality products, which is why we’re excited about this first annual PV Module Index from the Renewable Energy Test Center (RETC). The report is a comprehensive assessment of top-performing modules that are tested for reliability, performance, and quality across 18 different indicators. Within the data, two manufacturers — Panasonic and LONGi  — are recognized for demonstrating high achievement across indicators in all three categories.

“RETC is releasing this index to help the entire solar industry better evaluate modules based on important attributes beyond efficiency and cost,” said Cherif Kedir, RETC President and Chief Executive Officer. “It’s worth noting that high achieving quality module manufacturers put their products through an exhaustive set of accelerated reliability tests, while other manufacturers choose to select only a few of the tests to characterize their products. We congratulate the high achievers in each of the categories, and look forward to working with all manufacturers to continue to demonstrate their product excellence.”


In 2018, RETC tested more than 2,500 individual modules, from more than 150 different module families, made by 46 different suppliers. While RETC evaluated modules on 18 different criteria, the report focuses on eight important criteria that best represent the three categories of reliability, performance, and quality. The report calls out high achieving modules that demonstrated results at the top of the distribution for each of the eight criteria.

“As the industry has matured, solar professionals may want to focus on the cost per watt, but modules with the lowest price are not always top values in performance, quality or reliability,” said Chris Beitel, Head of Business Development at RETC. “By focusing on all three categories, module manufacturers can have confidence their products are well-equipped to perform across the board, while downstream players can feel assured the products they are selecting are engineered to deliver as expected.”

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The report provides data showing test results for modules that achieved results at the top of the distribution. The paper also shares data on new technologies, such as bifacial and PERC, more recent entrants to manufacturing, and the differences between laboratory testing and real-world field performance and reliability testing.

Here is a quick look at the tests performed and some of the high achievers in different categories. Be sure to get the full report


The PV Module Index reviews the results of module tests such as Damp Heat, Dynamic Mechanical Load, and Potential Induced Degradation. High achieving modules withstood abuse from these tests and saw minimal degradation in power output, versus their peers.

  • Damp heat high achievers: Jinko Solar and Longi Green Energy Technology.
  • Dynamic mechanical load: Manufacturers achieving lower than 1% of degradation in the DML test: Canadian Solar, CertainTeed, Hanwha Q CELLS, Jinko Solar, Longi Green Energy Technology, Mission Solar, Panasonic, and Trina Solar.
  • PID: The manufacturers who achieved in the Top 50%, less than 1.0% degradation through 196 hours of testing: Jinko Solar, Longi Green Energy Technology, Merlin Solar, Panasonic, and Solar Frontier.


These tests measure a module’s efficiency in power generation and see how they do in actual real-world conditions, such as high temperatures, and early morning and afternoon sun conditions. Tests conducted include I-V Characterization of Module Efficiencies, conditions at elevated temperatures such as PVUSA Test Conditions (PTC), and Pan File Testing, which evaluates modules in various light and temperature conditions. Seven high achievers demonstrated greater than 19 percent module efficiency.

  • Manufacturers that achieved greater than 19% total area module efficiency in 2018 include Hanwha Q CELLS, JA Solar, Longi Green Energy Technology, Panasonic, Solaria, Sunpreme, and Yingli.
  • Four high achievers received Performance Ratios above 85 percent by demonstrating simulated performance, via PVsyst software, which was 85 percent of their “nameplate,” or theoretical maximum output: JA Solar, Jinko Solar, LG, and Longi Green Energy Technology.

Commitment to quality

These tests indicate a manufacturer’s strict adherence to high-quality standards in their R&D process, engineering changes, manufacturing and vendor management. Quality products should be well manufactured with repeatable processes, materials, production equipment, and labor techniques.

To demonstrate quality, the PV Module Index provides an exhaustive characterization of a module family across a multitude of tests to develop its Product Qualification Program/Thresher Performance Matrix. Degradation of less than 2% for a given test demonstrates high achievement and four manufacturers reached this level of performance.

Additional tests that are discussed in the report that covers reliability include Humidity Freeze, Thermal Cycling and Ultraviolet Exposure. In performance, other tests include Incidence Angle Modifiers and Light and Elevated Temperature Degradation. Finally, in the area of quality, additional tests in the report cover Engineering Changes, Bill of Material Changes, Randomized Sampling, Factory Audits, and Factory Inspections.

The tests were completed at sites in Fremont, California; Pahrump, Nevada; Los Andes, Chile and in Cagayan de Oro City, in the Philippines.

— Solar Builder magazine

Solar Marketplace Report shows the power of one ITC and the weakness of another

The semiannual Solar Marketplace Intel Report from EnergySage shows that solar system costs continue to fall, despite the Trump tariffs, which so far, have not even produced more domestic module procurement. Here are four takeaways from this latest report, which is based on millions of transaction-level data points generated within the EnergySage Solar Marketplace during 2018.

Tariffs have no impact on domestic panel purchasing (yet)

energysage market intel solar report

In January 2018, the Trump administration acted on the U.S. International Trade Commission’s finding of “serious injury” to U.S. solar panel manufacturers by levying tariffs on imported solar panels. The tariffs were intended to help American-made solar panels better compete with their foreign-made counterparts.

However, a full year after the tariffs were announced, the number of quotes offering domestically produced panels reached near-record lows on the Solar Marketplace. Ultimately, just 4% of EnergySage shoppers purchased a system with American-made solar panels in 2018 – an all-time low in the history of the EnergySage Marketplace.

But many of the top panel providers are opening / have opened U.S.-based manufacturing facilities, so this mix could actually shift pretty dramatically in a future report.

In the meantime, Panasonic remains the most quoted / selected solar panel brand with LG coming in second. Among the U.S. manufactured brands, Solaria is on top, followed by Mission Solar.

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Cost of solar falls to $3.05 per Watt, with several markets trending under $3 per watt

In H2 2018, the average quoted cost of solar on the EnergySage Marketplace dropped 2.2% to $3.05 per Watt. This is the largest price drop seen on the Marketplace in two years. At the same time, the average size of quoted solar energy systems increased by 7%, up to 9.6 kilowatts.

Digging into this number further, the news is even better for solar in larger markets like Arizona, California and Texas, which are seeing sub $3 per watt costs regularly. In fact 45 percent of the quotes in EnergySage’s network fell below $3 per watt.

Florida is one state showing intense price competition, with an average cost per watt of $2.72. On the other end of the spectrum, the Northeast is still seeing some of the higher solar system costs in the country.

ITC step-down could erase price decreases from previous year

The federal Investment Tax Credit (ITC) will decline to 26% at the end of 2019, which may effectively erase a year’s worth of solar cost decreases. The installed cost of solar could increase by over $1,000 for the average residential solar shopper come January of 2020.

Solar interest grew in all 50 states

Consumer interest in solar increased across the country, with interest doubling in 11 states between 2017 to 2018, according to an analysis of EnergySage website traffic. Virginia led the nation with the most year-over-year growth in solar interest, with Nevada a close second.

“Consumer interest in solar has proven incredibly resilient over the past year, despite tariffs and other attempts by the current administration to artificially decrease demand,” said EnergySage CEO and founder Vikram Aggarwal. “Solar prices are continuing to fall as installers improve their operations, supply chain management, and sales strategies. Additionally, we expect the growing popularity of brands like Enphase, LG, Panasonic, SolarEdge, and SunPower to lure more American consumers into the residential solar market in years to come.”

— Solar Builder magazine

Panasonic’s HIT AC module featuring Enphase microinverters shipping soon

panasonic enphase

The new Panasonic AC Series Photovoltaic (PV) HIT N330E AC Module with integrated Enphase IQ 7X Microinverter will be available for solar installation companies in late March.

“In today’s market, solar installers look to offer homeowners high powered and efficient modules that maximize output on roofs of every shape and size,” said Mukesh Sethi, General Manager, Solar, and Energy Storage Division, Panasonic Eco Solutions North America. “Our AC module partnership with Enphase Energy allows us to combine our award-winning, high-efficiency PV modules with the highly reliable seventh-generation Enphase IQ microinverters. We are certain that together we will achieve tremendous efficiencies and add value to the residential solar industry, for both solar installers and solar homeowners.”

What’s cool about it

Panasonic’s N330E HIT AC Series Modules combines the efficiency of HIT solar panels with the intelligence of Enphase microinverters. One of the most efficient panels on the market, the N330E HIT AC series features high power outputs and greater energy yields due to their industry-leading temperature coefficient of -0.258%/⁰C.

The N330E features an integrated seventh-generation Enphase IQ 7X microinverter. Panasonic HIT® N330E AC Series Modules are guaranteed to keep at least 90.76% of their initial power output, driving value and peace of mind for customers who benefit from the 25-year Panasonic TripleGuard warranty on panels and the Enphase Energy Limited Warranty on the microinverter.

Panasonic AC Series HIT N330E Modules based on Enphase IQ microinverters meet or exceed regulatory requirements set by the National Electrical Code (NEC) and individual states and are certified compliant with NEC 2014 and 2017 rapid shutdown requirements.

“The IQ 7X™ micros and Panasonic HIT modules are already our flagship combination, and the Panasonic N330E AC modules will now significantly reduce our install times and provide savings on logistics and overhead costs in the warehouse,” said Arno Aghamalian, CEO, Solar Optimum Inc.

roof top reportDownload the new Residential Rooftop Report to heat up your solar sales

The Residential Rooftop Report for the first quarter of 2019 is now available for download. The theme is “Heating Up Sales,” and we’ve teamed up with report sponsor Aurora Solar to examine ways for residential solar installation companies to lower customer acquisition costs, close more leads and overall run a more streamlined, efficient local solar business. Just fill out the form below to access your free report.

— Solar Builder magazine

Module Buyer’s Guide: 10 modules to know in 2019

module buyer's guide

For our 2019 Module Buyer’s Guide (included in the Jan/Feb issue of Solar Builder magazine) we rounded up profiles on the newest modules on the market and also surveyed solar module manufacturers on the trends they are seeing and some of the new technology to watch. The seven insights are here, and you can check out the new products below.

Mission Solar

To pack as much power as possible in order to dramatically reduce energy costs, Mission Solar developed the MSE PERC 60 module. The MSE PERC 60 features a compact 60-cell design that is smaller while packing 310 W of power. This module is best suited for residential and commercial projects. Warranty: 25-year performance and 12-year workmanship. More Mission Solar news here.

mission solar



CertainTeed says it expects to launch half-cut cells in Q2 2019. The new module will consist of standard PERC mono cells, cut in half, connected in series and parallel to achieve similar voltage and current characteristics as standard 60-cell modules at the module level. Warranty: 25-year linear power output, and a 25-year workmanship warranty when installed by certified contractors. More CertainTeed news here.




Hanwha’s new Q.PEAK DUO BLK-G6 module will be assembled in the U.S. at Hanwha Q CELLS’ new Dalton, Ga., module facility — the largest module manufacturing facility in North America — slated for completion in January. The 6×20 monocrystalline Q.ANTUM half-cell design allows for higher yield per surface area and higher power classes. The Q.PEAK DUO is ideal for residential applications. Warranty: 12-year product, 12-year linear performance. More Hanwha Q Cells news here.



LONGi Solar

The combination of elements in LONGi’s Hi-MO — a half-cut, p-type, monocrystalline PERC, bifacial module — is compelling. LONGi says the bifaciality results in a 10 to 25 percent higher yield at a cost similar to a monofacial PERC module. The bifaciality factor, which is the ratio of efficiency on the rear side as compared to the front, is upward of 75 percent. These are ideally suited for utility power plants and commercial rooftop applications and areas with a greater surface albedo. Warranty: 30-year for extra linear power output, 10-year for materials and processing. More LONGi news here.



Trina Solar

Trina Solar’s DuoMax Twin is its half-cut, bifacial mono PERC offering. It uses heat strengthened glass in lieu of the polymer backsheet used in other modules. The dual-glass construction provides better protection for the cells and improves the long-term reliability and durability of the module. Also, the Duomax Twin’s junction box avoids shading on the backside of the panel. Trina has extended the power warranty to 30 years. Warranty: 10-year product and workmanship, 30-year linear. More Trina Solar news here.

trina solar


Silfab’s SLA-MWT 320 W (Metal Wrap Through) technology removes all stringing and bussing from the front side of the module by integrating a conductive metallic layer to the backsheet for the purposes of conveying current to the junction box. This reduces both resistance and cell shading which ultimately yields higher module efficiency. By removing the conventional stringing process from the module production line, operational efficiencies can be recognized. Ultra-high efficiency modules are optimized for both residential and commercial projects where maximum power density is preferred. Warranty: 25-year product, 30-year performance. More Silfab Solar news here.



The Panasonic N340 HIT + Series with its heterojunction technology and enhanced 40-mm frame offers customers increased module efficiency, performance and longevity while maximizing available roof space. The new 40-mm frame increases durability and strength, being able to handle loads of up to 5,400 Pa. Also, the water drainage system gives rain water and snow melt a place to go, reducing water stains and soiling. Warranty: 25-year workmanship and linear power output. More Panasonic news here.


REC Solar

The REC N-Peak is the world’s first solar panel combining n-type mono half-cut cells with a twin-panel design, featuring zero LID, REC’s best warranty and super-strong frame design for loads of up to 7,000 Pa. Combined with n-type, REC’s PERT technology completely passivates the rear of the cell for increased electron capture and high and stabilized efficiency. The N-Peak is especially suited where space is limited, such as residential and commercial rooftop installations. Warranty: 12-year product, 25-year linear power output.

rec solar


LG’s “V5” series of modules is slated to enter the market in Q2 with some incremental product improvements, in addition to an enhanced warranty, which has one of the lowest degradation rates, and a 25-year product and performance guarantee. NeON2 “CELLO” cells, which have Cell connection with Electrically Low Loss and Optical Absorption Enhancement, create greater yield and less reflection through increased usable surface area on the front of the cell and greater reliability if the cells were to become micro-cracked. Warranty: 25-year linear, extended to 89.6 percent performance. More LG news here.



Solaria is unique in that it built what it considers to be the perfect residential module, the PowerXT, and offers it as is or as an inverter-integrated AC version. Solaria uses proprietary manufacturing to singulate its mono PERC cells into uniform strips that are then re-assembled into high-density PowerXT cells. The PowerXT comes in a pure black appearance and uses proprietary technology to eliminate bus bars, so there’s no visible circuitry and fewer failure points. Warranty: 25-year linear power output and workmanship. More Solaria news here.


— Solar Builder magazine

Photovoltaic-aways: Solar module manufacturers share 7 insights on PV market trends in 2019

solar module manufacturing

For our 2019 Module Buyer’s Guide (included in the Jan/Feb issue of Solar Builder magazine) we rounded up profiles on the newest modules on the market and also surveyed solar module manufacturers on the trends they are seeing and some of the new technology to watch. The seven insights are below, and you can check out the new products here.

1. Mono PERC power

Passivated Emitter Rear Cell (PERC) is a photovoltaic design that increases light capture efficiency by adding a passivation film at the rear end of the cell to capture scattered and reflected light. An obvious benefit of PERC technology is that it allows for high-power modules, and the more power a module produces, the more money that can be saved by reducing overall BOS costs. Using high-power modules can mean fewer panels, less racking, wiring, combiner boxes and reduced labor hours.

One step further, half-cut cells have reduced resistive losses, which makes them capable of boosting power output by another 5 to 15 W per module depending on the cell type. The shift to monocrystalline solar modules is accelerating faster than expected, with mono PERC to witness the largest market share increase. In 2017, half-cut cell solar panels took 11 percent of the global module capacity, and this share is expected to rise to around 35 percent by 2020.

2. Bifacial boost

The buzziest of buzzy PV module technology right now is some combination of mono PERC and half-cut cells with the innovative application of bifacial module design.

“Recent projects incorporating this combination dropped levelized cost of electricity so rapidly that the biggest barrier to grid parity for utility-scale photovoltaic plants is not the cost of technology but rather the soft costs related to grid integration, land, labor and legal fees,” LONGi Solar tells us, which has broken world records for PERC cell and module technology eight times since September 2017. “Better, more efficient products on the market will free up resources for other types of innovation in the solar industry.”

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DNV GL, the world’s largest resource of independent energy experts and certification body, was just selected to receive a $200,000 award from the U.S. Department of Energy (DoE) Solar Energy Technologies Office (SETO) to research bifacial PV technology.

“The aim of the study is to accelerate commercial deployment of bifacial PV modules at scale,” says Tara Doyle, head of business development for DNV GL’s PV module testing lab [now PVEL]. “If proven viable through extensive performance and reliability testing, bifacial PV modules have the potential to become the preferred technology for ground-mounted PV installations around the world.”

The project will entail the collection of field data over the course of one year at DNV GL’s outdoor solar test facility in Davis, Calif. It will include bifacial and monofacial 1500V PV modules provided by LONGi Solar, Astronergy Solar, Hanwha Q CELLS and Trina Solar, tested on single-axis trackers provided by solar tracking company NEXTracker, and two albedo ground types. Data acquisition will be highly granular, using actively calibrated equipment. The collected measurements will be used to generate PAN files and subsequent energy simulations using PVsyst.

3. Economics over efficiency

Counter to the half-cut movement is the idea that chasing that extra bit of efficiency juice isn’t worth the squeeze, so to speak. Silfab Solar is taking a different approach, believing the tinkering with the glass size and cell cut of conventional mono and mono PERC technologies won’t result in enough efficiency gains. Instead, Silfab is focusing on the adoption of next generation technologies that could allow material gains in module wattage while maintaining attractive price points, such as metal wrap through (MWT) and interdigitated back contact (IBC).

Silfab says the practice of leading with a high priced premium brand and following up with a low price economy brand in price-conscious situations can lead to reduced revenues and margins.

“There are price effective premium brands that allow EPCs to standardize on a single module partner, recognize better revenues in cost-conscious scenarios (like larger system sizes) and recognize better margins on the remainder of the system in terms of premium value/wattage without premium pricing,” Silfab tells us.

4. Lifetime value

Efficiency numbers in lab conditions and coming out of the box get the biggest headlines, but for an investment that degrades over its 25-year lifetime, it’s not the most impactful metric on its own. Other module lifetime considerations such as warranty terms, temperature coefficients and degradation rates are now winning the day in many segments but especially in residential. EPCs and installers that only look at one facet, such as price or rated DC capacity, are doing themselves and their customers a disservice. While those factors are important, selling certainty over 25 years is more valuable overall.

“Often we hear from our customers that they made the mistake of only looking at the price per watt when choosing a PV module,” notes the team at Trina Solar. “Then they found that they had increased operations and maintenance costs down the road, and that the company they had bought from is no longer around to honor the warranty. Unit cost is important to consider, but if you neglect to look at things like performance, quality standards and company bankability, you may end up paying for it later.”

5. Reduced degradation

Pay attention to that temperature coefficient and light induced degradation (LID) rate because these are huge factors in the actual energy generated throughout a day and over a project’s useful life. Initial field tests carried out by the Solar Energy Research Institute of Singapore (SERIS) have shown that n-type cell technology, specifically REC’s new N-Peak, reduces LID to zero, meaning no power loss right after installation. This provides improved performance in shaded conditions and allows flexible installation options. Similarly, Panasonic’s HIT n-type solar cells have extremely low LID and zero potential induced degradation (PID). Panasonic’s technology reduces annual degradation to 0.26 percent compared to 0.70 percent in conventional panels. This is why Panasonic guarantees a minimum 90.76 percent rated power output after 25 years.

In 2018, SunPower hit the industry’s lowest solar panel degradation rate, according to a calculation method developed in partnership with the National Renewable Energy Laboratory (NREL). When this method was applied to eight years of energy performance data from 264 SunPower solar systems operating at various locations worldwide, it proved that SunPower panels degrade at a median rate of 0.2 percent per year. The company’s P-Series solar panels will soon to be manufactured in America.

6. Aesthetics

Value is often in the eye of the beholder, and as residential solar adoption widens and as the new build market explodes in California, aesthetics of rooftop panels will matter more and more. This is why all of the top residential module manufacturers now have an all-black version of their flagship product, which are often priced a tad higher.

Similarly, thin-film PV could be on the upswing in the U.S. residential solar sector. Swedish solar energy company Midsummer reports that it has received an order from Sunflare for equipment for the production of thin film solar cells worth over $7 million. Midsummer’s DUO system is one of the most widely distributed manufacturing tools for flexible CIGS solar cells in the world. Sunflare, with global headquarters in La Verne, Calif., is a provider of flexible mass-produced thin film solar products that are especially suitable for weak roofs and new roofs for private homes.

“The demand for our products in the U.S. has exceeded our expectations and we rapidly need to expand our production capacity with the help of our established partner Midsummer,” says Philip Gao, CEO of Sunflare.

7. Tariffs

The administration imposed steep import tariffs on virtually all crystalline silicon based solar modules in 2018. Additionally, many of the other materials used in solar panels now also face duties as part of a 10 percent levy on about $200 billion worth of Chinese goods that went into effect in September. The tax on these imports was expected to rise to 25 percent on Jan. 1, 2019, adding additional burden even to U.S.-made solar modules.

Finished solar panels require scores of components, ranging from aluminum framing to transformers, solar glass and power inverters. Solaria’s CEO Suvi Sharma estimates that U.S. tariffs this year have increased the company’s U.S. production costs by about 30 percent — an amount equal to the original U.S. solar panel import duty.

As a consequence of the tariffs, Solaria abandoned its plans of boosting production this year at its plant in Fremont, Calif. Due to capital expenditures imposed by the tariffs, the company was unable to expand its workforce in the U.S. as planned.

LG does not manufacture cells or modules in China, but it too was impacted by the tariffs in 2018. In response to this the company is committed to establishing a 500-MW production facility in Huntsville, Ala. Although this was in the works prior to the announcement of the tariffs, due to the strong market demand from the U.S. and LG’s desire to be closer to its customers, the tariffs certainly accelerated the process. The first modules manufactured in Huntsville will be rolling out in Q1 this year.

— Solar Builder magazine