SolarReviews releases a new scoring system to rank the best solar panel manufacturers of 2021

Updated

SolarReviews is proud to announce the release of its new Solar Panel Manufacturer Scoring System. It is the first such system that scores solar manufacturers across a wide range of objective criteria.

The scoring system has been formulated after extensive discussion with industry leaders and offers a transparent and unbiased scoring methodology for solar brands. It has been used for the first time to score the SolarReviews 2021 Top 20 Solar Panel Manufacturer Rankings.

The rankings are designed to provide homeowners insight into the likely quality and performance of solar panels over their full life. The term 'full life' is key here, as solar panels are a long-term investment with a warrantied life of between 25 to 30 years.

Why was an expert scoring system needed for solar panel manufacturers?

After running a reviews website for the solar industry for many years, it was clear to our editorial committee that consumer reviews alone were not enough to offer sensible advice to consumers about their choice of solar panel brand. An expert rating system was needed to judge criteria not visible to consumers.

We don't just judge a manufacturer's current product line, but also its financial health, the likelihood it will be around over the next quarter-century to honor warranty claims, and the quality of the solar panel installation companies that choose to install each brand. (Consumer reviews, as useful as they are, are typically written within the first year of the panels‘ life, and therefore aren't as good at predicting solar panels’ performance over time).

Read on to see the full list of ranking factors, along with explanations of why they are important to homeowners and how each was scored. 

The assessment was conducted based on facts and information available as of June 30, 2021.

Ranking factors

Below is a list of the criteria we used to judge solar panel companies and the weights we assigned to each.

  • Value (30%): Solar panels are a substantial investment, and their high upfront cost deters many homeowners from going solar. As such, we think solar panel cost is a significant factor to consider when rating solar panels.
  • Module quality (20%): This is an assessment of the spec sheet performance of each company's top residential solar panel, specifically their efficiency rating and temperature coefficients. Panels that take up less space and perform more consistently in different climatic conditions will earn a higher score.
  • Financial visibility and strength (20%): This factor assesses the financial health of the solar panel manufacturer. This serves as the best possible indicator of whether the company will be around to honor any warranty claims that may arise.
  • Warranty (10%): Here, we look at both the product and performance warranty. The former reflects the reliability of the module, while the latter tells you how panel performance will hold up with each passing year.
  • U.S. investment (10%): This factor assesses how committed each brand is to the U.S. market.
  • Dealer network (10%): This reflects the availability of the brand among solar installers.

Let’s take a deeper dive into each category and see how we assigned scores for each.

Robot arm holds solar panel in a high-tech factory

In the U.S. investment ranking factor, manufacturers with production facilities in America earn higher points. Image source: Jacksonville Daily Record

1. Value - 30%

Points assigned for: Cost per watt

To ascertain the value proposition of each solar panel brand, we assigned points based on the cost per watt of their flagship solar modules as of the time of scoring (June 30, 2021). The lower the cost per watt, the higher the score.

Comparing solar panel brands based on cost per watt is the standard in the solar industry. Cost-per-watt figures are useful as they allow a like-for-like comparison between solar panels of different power outputs, For instance, a 6,000 watt system built of 20 x 300-watt panels, or 15 x 400-watt panels; instead of comparing the cost per panel, looking at the cost per watt is much more meaningful.

We found that the solar panel brands offering the best value (AKA the cheapest) were roughly half as expensive as the brands offering the lowest value (AKA the most expensive).

Highest scores for value: JA Solar, LONGi, Yingli, Axitec
Lowest scores for value: SunPower Maxeon, Panasonic, Solaria, Seraphim, LG Solar

2. Module quality - 20%

Points assigned for: Panel efficiency; Temperature coefficient

When judging module quality, we decided to focus on the two most important items on the specifications sheet: panel efficiency and temperature coefficient of Pmax. Each factor accounts for half the total points in this category.

Panel efficiency measures the amount of sunlight that gets converted into energy. A panel with a higher efficiency rating requires less space to produce a given amount of energy, reducing its physical footprint, or taking up less space. (We have an in-depth blog explaining panel efficiency here).

Temperature coefficient of Pmax tells us how well a panel will perform in real-world temperatures. The lower the temperature coefficient, the better - as this means there is less power loss for every 1°C that the panel is hotter than 25C. (Panels run about 20°C hotter than the ambient outdoor temperature, so your panel will almost certainly be running at higher than 25°C for most of the year).

These two factors are not just meaningful on their own; they also speak to the solar panel’s overall production quality. For a company to achieve high efficiency rating and low temperature coefficients, they need to employ advanced, highly-automated manufacturing processes.

Highest scores for module quality: LG Solar, SunPower Maxeon
Lowest scores for module quality: Hyundai, Boviet

3. Financial visibility and strength - 20%

Points assigned for: Public listing; Availability of financial statements; Operating revenue and profitability

This category could just as well be called, 'How likely is it that the solar panel manufacturer will be around for the next 25 years?’

This question is important because solar panels are a unique product - they are designed to work for decades, and manufacturers guarantee a certain level of performance for a period of 25 years.

We answer the question by looking at several indicators of financial health.

The first step is to determine whether the company’s financials are visible, and therefore easy to assess. Companies that publish their financial statements, or are publicly traded, get more points.

Next, we look at revenue. We assign points to companies based on the size of their overall revenue, as we deem larger manufacturers more likely to survive. Large manufacturers with revenue north of $2 billion earn the maximum number of points, while smaller players with under $100 million in revenue earn the least.

Finally, we look at profit. We assign extra points to companies that reported a net profit in the most recent financial year. The logic here is simple: companies that are profitable have the best chance of staying in business and expanding, while those that are unprofitable have less rosy future prospects.

Some of the manufacturers we’ve rated are private or wholly-owned subsidiaries of larger groups that offer no visibility into their financial position. Where this was the case, we looked at the financials of their parent company, but discounted these scores by half. Our logic is that while a subsidiary can benefit from the resources of the parent company, and deserves some points for being part of a large and/or profitable company, a subsidiary is also at risk of being spun off if it is not profitable.

Highest scores for financial visibility and strength: LG Solar, QCells, LONGi, Jinko Solar, Canadian Solar, JA Solar, Trina Solar
Lowest scores for financial visibility and strength: Silfab Solar, Axitec

4. Warranty - 10%

Points assigned for: Product warranty length; 25-year performance warranty

The manufacturer's warranty is an important consideration when buying a product like solar panels, since they are built to last for a quarter-century or longer.

When it comes to product warranties, we’ve awarded higher points to the brands that cover the longest time periods, i.e. between 20 to 30 years. [We examine the warranties of leading brands in this article].

For the performance warranty, we’ve also assigned the highest points to solar panels that have the lowest degradation rates, which means they will see the smallest output drop-offs over their warrantied lifetime. The panels that scored highest here indicate that they will produce 90% or higher of their rated output at the 25-year mark.

You may be wondering why we’ve decided to limit the weightage of warranty in our scoring system to just 10%. The reason is simple: while warranty promises are useful, we believe that the company’s ability to honor the warranty is what really matters, a fact which is best reflected by their financial visibility and strength score.

Highest scores for warranty: SunPower (Maxeon), REC Group, Panasonic, LG Solar
Lowest scores for warranty: Hyundai, S-Energy, Boviet, Yingli

5. U.S. investment - 10%

Points assigned for: Headquarters or offices in the U.S.; American manufacturing; Attendance at U.S. trade shows and events

Many consumers place priority on buying local and supporting the local economy. As such, we’ve assigned more points to companies that have their global headquarters in the U.S., with lesser points if they only have offices here. We also awarded extra points to manufacturers with solar panel production facilities here in the U.S., as well as for recent attendance at major American trade shows and industry events.

The companies that score highest in this category are American-headquartered companies with local production facilities. However, some big foreign manufacturers score relatively highly as well, having spent hundreds of millions of dollars to set up U.S. factories and strengthen their local marketing and support.

Our logic here is that if a company has spent a lot of money building up its brand equity in the U.S, they are more likely to honor warranties to protect the reputation of their brand. 

Highest scores for U.S. investment: Mission Solar, Solaria
Lowest scores U.S. investment: Phono Solar, Hyundai, Yingli, JA Solar, SunPower Maxeon

6. Dealer Network - 10%

Points assigned for: Share of residential installations

A manufacturer may offer great solar panels, but this is of little use if local dealers and installers don’t carry their product. As such, we’ve decided to give 10% weightage to product availability and the quality of the installers that recommend the brand. We’ve assigned scores on a sliding scale based on brand market share in California between January 2018 and April 2021.

The companies that scored the highest each accounted for between 14.2% and 17% of California home solar panel installations over this period.

Highest scores for dealer network: SunPower Maxeon, QCells, LG Solar
Lowest scores for dealer network: Seraphim, JA Solar, Yingli, Phono Solar

See live prices for solar panels from the best solar manufacturers
 - Author of Solar Reviews

Zeeshan Hyder

SolarReviews Blog Author

Zeeshan is passionate about promoting renewable energy and tackling climate change. He developed these interests while studying at beautiful Middlebury College, Vermont, which has a strong focus on sustainability. He has previously worked in the humanitarian sector — for Doctors Without Borders — and in communications and journalism.

Related solar news