There are many module manufacturers and products on the market today, and it can be a challenge to find the best products with the right warranty coverage for a specific project from a financially stable manufacturer. For solar panels (known as “modules” in the industry) this typically is defined as a “Tier-1” or “bankable” module.
Some financial consultants, such as Bloomberg, publish their own listings of Tier-1 modules. The manufacturers have to pay to submit their qualifications, and users have to pay to buy the ratings list. The criteria to be a Tier-1 module, according to Bloomberg, is to document at least 6 projects that were financed by a bank in the last 2 years, with each one being at least 1.5 MW in size. That is a very low bar for sure, and probably hundreds of module manufacturers would qualify as “Tier-1” if they submitted their data for publication.
We encourage a more careful approach to module selection. Questions we ask involve an assessment of the strength of the company itself (its financial condition and operating history), and then look at the products specifically. For instance, does the manufacturer have any legal actions or product recalls on record. Then, how long has the manufacturer been in business and did they enter the solar module business through deliberate growth, or part of a merger or acquisition.
Out of the possible hundreds of “bankable” module manufacturers, typically a few dozen clear our stricter hurdles. Below are the criteria and questions we ask before deciding to buy a solar module.
We then use this analysis to calculate the effective cost of energy, in kWh, for the system. This energy unit measure is much more important than the typical $/Watt power metric. The power unit metric really is irrelevant, although the market focuses on it. Just like the misguided habit of focusing on Bloomberg to define what is a “Tier-1” module.
|Warranty||Linear warranties provide consistent and uniform performance, resulting in 7% to 10% more guaranteed power production than a step warranty. Modules should have independently verified PAN files for performance modeling. Is third-party re-insurance available, such as “PowerGuard”.|
|Positive Power Sorting||Power range, specified as a percentage +/- range of the rated power. “Positive sorted” module (+5W/-0W, for instance) will deliver no less than nameplate rating. A neutral power-sorted module (+/- 5W, for instance) means it may be higher or lower than its rated power. “Positive” power sorting delivers 2% to 3% more power than “neutral” power sorting.|
|Module Efficiency||Higher efficiency modules can produce the same amount of electricity from a smaller module. This is important only if the space for the array is very limited and the project’s goal is to make the most electricity from the smallest array footprint, such as small residential roofs. Otherwise efficiency is not an important criterion.|
|Lifetime Energy Yield||How much electricity the module is expected to produce over its lifetime compared to its rated power. This is a combination of the warranty, power sorting, and temperature performance.|
|Performance in Hot and Hazy Conditions||Module performance is peak with clear sunlight and cool weather conditions. Power decreases somewhat as temperature or hazy conditions increase. This is reflected in the “PTC” rating and how close that rating is to the “STC” power rating. This is best analyzed using PVSyst or similar analytical software and the PAN data for the specific module.|
|Durability||Modules comply with IEC 61215 or UL 61215 for durability testing.|
|Reliability||Documentation of extended reliability testing program, with independent oversight.|
|Field Performance||Confirm the return rate for the modules is no greater than 0.005%.|
|Potential Induced Degradation (PID)||Modules that use quartz glass, avoid EVA encapsulation and PVB laminate are PID resistant. Manufacturer should provide documentation showing PID limitation.|
|Corrosion Resistance||This applies to the frames, hardware, and sealing of the junction box, in addition to consideration of the project site. The aluminum should be anodized and bent/broken only before anodizing. Hardware should be stainless steel, grade 304 or higher. J-boxes have to be permanently sealed or potted. Frameless panels have excellent corrosion resistance.|
|Dimensional Tolerance||Module frame dimensions have to be held within 3mm corner to corner.|
|Fill Factor||The fill factor is the ratio of actual MPP Power to the theoretical maximum power as the product of the open-circuit voltage and short-circuit current, and is the measure of internal power losses (higher fill factor means lower internal losses). Target is > 0.75. Below 0.7 fill factor is considered poor performance. Can be measured with IV-curve device or from technical specifications.|
|ISO-Certification||Is the manufacturing plant ISO-9001 and/or ISO-14001 certified. The -9001 certification denotes quality assurance, and -14001 denotes environmental performance. If not 9001, does manufacturer have an audited quality management system.|
|Energy Payback||The length of time the module must be in service to produce the energy required to manufacture the module. Target is 2 years.|
|Recyclability||Consideration of the quantity and recyclability of the shipping materials.|
|Origin & Manufacture||Origin & manufacture can apply to the raw materials, component parts, or final assembly of the modules. “Buy-American Act” compliance means that more than half the material components are made in the US.|
|Company Financial Strength||This is the most difficult measure to quantify. Combined consideration of investment analysts’ published opinions, Altman-Z Score (if available), whether the company has a reserve account for warranty obligations and the capitalization of that account, or whether there is a third-party company backing up the warranty and to what extent. The Altman-Z score should be calculated over at least 3 years with the trend noted.|
It takes a lot of effort and engineering to vet a manufacturer and a product – but we do that so our clients get the level of quality and reliability and durability that they want.
Buying a second-tier module can save 3-5% of the project’s first cost. But making that small investment in higher quality almost always delivers better performance over time: more energy, higher financial returns, less downtime, less maintenance, and a lower overall cost of energy