the stacked up solar panels with an energy efficiency chart on top

Understanding Solar Panel Efficiency

Understanding the Fundamentals of Solar Panel Efficiency


Written by qualified solar engineer Leonardo. Last updated:

Typical solar panel efficiency ranges from 15% to 20%, and the most efficient solar panels commercially available are slightly above 22%. Some laboratory prototypes have reached efficiency values over 40%, but they are still very expensive and not viable for commercial use.

In simple terms, solar panel efficiency can be described as the conversion rate from sunlight to electric power. If solar panels from many brands are exposed to the same sunshine, the ones with the highest efficiency will produce the most kilowatt-hours per day.

The efficiency of solar panels is often misunderstood, and a value of 20% may seem small when some natural gas power plants are above 50%. However, there is an important difference:

What Does Solar Panel Efficiency Mean?

The solar panel efficiency describes how much sunlight is converted into electricity. For example, if you place a panel that is 20% efficient under 1,000 watts of sunshine, it will produce 200 watts of electricity.

picture of half a house and half a chart of energy efficiency

In this case it may seem that 800 watts are being wasted, and solar panels often get criticism for their low efficiency. However, consider that all 1,000 watts of sunlight were being wasted before! It would be more correct to say that solar panels obtain electricity from an abundant resource that is otherwise wasted. The outlook for fossil fuels is very different, since all inefficiencies result in wasted fuel, operating expenses and greenhouse gases.

You can use solar energy even if your panels are at the lower end of the efficiency scale. In fact, a lower efficiency often makes the solar system more affordable, and you may get a shorter payback period. If your panels are from a quality brand and covered by solid warranties, your project can be successful even with modest panel efficiency.

What Is the Average Solar Panel Efficiency?

As of 2019, the average solar panel efficiency is from 15% to 20%, but consider that some manufacturers have panels that fall outside this range. The SunPower brand has the current solar panel efficiency record among commercial products, at 22.8% conversion efficiency from sunlight to electricity.

Solar efficiency is provided by manufacturers along with panel specifications. However, you can compare them more easily by looking for a solar panel efficiency chart from a trusted source, such as the National Renewable Energy Laboratory (NREL).

Energy efficiency gets a high priority when deciding if solar panels are worth it. However, keep in mind that a higher efficiency often comes with an increased price. In this case, you must make sure that the additional savings compensate the additional costs.

  • A good recommendation is asking solar companies to provide a financial analysis along with their proposals.
  • The solar panels that achieve the highest return on investment and the shortest payback period will not necessarily be the most efficient ones.

When comparing your options, also make sure you are looking at solar panel efficiency 2019 data. Manufacturers are constantly investing in research and development, to improve the efficiency of their solar cells.

How to Calculate Solar Panel Efficiency?

Solar panel efficiency is calculated with a set of Standard Test Conditions (STC), which are used by the entire solar industry. They are tested in laboratory conditions, with a light source that provides 1,000 watts per square meter, and a solar panel surface temperature of 25°C. Also, the test light source must closely replicate sunlight that has moved through the atmosphere.

When solar panels are installed on homes and businesses, the site conditions differ from the idealized lab conditions. As a consequence, the actual efficiency achieved by solar panels differs from the laboratory efficiency. However, the standard efficiency rating is very useful to compare solar panels under equal conditions.

calculator working out the efficiency of solar panels on a home

Solar panels can also be tested under other conditions called NOCT, which stands for Nominal Operating Cell Temperature. These conditions are designed to simulate a typical project site:

  • A light source that provides 800 watts per square meter.
  • An air temperature of 20°C with a speed of one meter per second.
  • The panels are mounted with an open back side, to allow air circulation.

The NOCT efficiency test considers factors that are ignored in the STC test. However, keep in mind that both are reference values for panel efficiency. To know the exact performance that solar panels can achieve in your property, you must get a professional design that is based on a site assessment.

How to Increase Solar Panel Efficiency?

Solar panels have become more efficient as the manufacturing technology for solar cells has evolved. This factor is beyond the control of the homeowners and businesses who use the panels. However, smart design decisions can also improve the efficiency of a solar energy system.

The solar panel angle efficiency loss is a very important factor during the design process. The orientation of solar panels affects efficiency, and electricity production is increased when they are placed optimally:

  • Solar panels that receive sunlight head-on produce more electricity that those getting sunshine at an angle.
  • Ideally, the panels should have an orientation that maximizes efficiency in the presence of direct sunlight.

Solar companies use several software solutions that calculate the solar panel angle for maximum efficiency. If you live in the northern hemisphere, the south-facing side of your roof will typically get the most sunshine, unless an obstacle is casting a shadow. For countries in the southern hemisphere, the north-facing side of the roof is preferred.

Ground-mounted solar panels have more flexibility with respect to their orientation. Solar companies can calculate the exact angle that maximizes electricity production, to adjust the racking accordingly.

Working with a qualified solar company is important, since the installation quality is just as important as the solar panel quality.

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How are Solar Panels Rated?

How Are Solar Panels Rated?


Written by qualified solar engineer Carlos. Last updated:

The solar industry rates solar panels based off of factors such as wattage, efficiency, temperature coefficient, tolerance. Rates are also based off of more financial parameters like the tiering system, which is useful to measure and compare solar panels.

New solar panel models come out every year and add themselves to an extensive market with hundreds of modules and technologies, sometimes even combined with other products such as solar LED flood lights. However, when you go out to purchase solar panels, you might get overwhelmed with so many brands, models, and technologies.

Establishing a rating system is essential for the industry because this allows solar panel buyers to compare performance between different modules, and it establishes an equal ground base for the development of the industry. Solar panel buyers should fully understand the decision factors that must be taken into account when choosing modules based on their ratings. This is not only important when you choose a solar panel for your home or RV, but also if you are choosing a module to charge solar backup generators.

These ratings are referred to lab conditions that test the performance of modules under specific parameters, equal to all manufacturers. The performance of the solar panel under such conditions will determine how good or bad it is when compared to other models. We can divide these lab tests into two categories: STC and NOCT.


Standard Test Conditions (STC) are referred to lab tests for solar panels evaluated in a solar simulator called flash tester. During the test, the modules are exposed to artificial sunlight with an irradiance equal to 1,000 W/m2. This irradiance value is associated with the maximum solar radiation typically at noon and assuming the Sun directly reaches the module. Moreover, the temperature of the module is established at 25°C and the atmospheric density or air mass is equal to 1.5 (shortest optical path length of sunlight through the Earth atmosphere).


Nominal Operating Cell Temperature (NOCT) was established because STC tests did not represent real-world conditions under no circumstance. Therefore, NOCT acts as a better reference for utilities and other government entities of how the module would perform under normal or real-world circumstances, this allows them to establish rebates and tariffs more accurately.

NOCT assumes irradiance values of 800 W/m2, an atmospheric density of 1.5, an ambient temperature of 20°C, an operating temperature of 45°C and a wind speed of 1 m/s to represent air circulation on the backsheet (ground mounted systems).

All solar panel manufacturers must include in their datasheet the results of both STC and NOCT tests which outputs include: power, open circuit voltage, maximum power point (MPP) voltage, short circuit current, and MPP current. From these results, the most important one for reference in solar panel ratings is power. It is advisable to learn a little bit about how solar panels work to fully understand the meaning of these parameters.


Solar panels can be rated according to their wattage or power output. Lately, the industry has been pushing forward new modules with 400 W output or more, however, the big market share of solar panels is generally located between 300 W and 400 W.

Some solar panel manufacturers still produce power outputs around 250 W that can have residential applications. Power outputs below 200 W are generally attributed with off-grid applications, for RV’s or battery charging. Here we can see average power outputs of several manufacturers from June 2018.

bar chart to show the average solar panel wattage

Average solar panel wattage as of June 2018. (Source – Solaris-Shop)


Maybe the most common solar panel rating is referred to efficiency. This parameter acts as a reference of how much solar radiation can be transformed into electricity, generally tested under STC.

Given its importance, many homeowners, solar designers, and manufacturers rate the industry of solar panels according to the efficiency of modules. Only top-rated brands can produce the top solar panel efficiency, which is why every year there is a race or competition between manufacturers to release the ultimate and most efficient solar panel. We have developed our own top solar panel efficiency list according to the latest product releases of 2019.

Temperature Coefficient

The temperature coefficient is another common rating used to compare solar panels. They are referred to the changes in power, voltage, and current of the module due to the changes in operating temperature of the module. There are three of them in every solar panel. The most negligible is the current temperature coefficient because changes in temperature do not represent important changes in current.

There are also the voltage and power temperature coefficients which effect is deeply important because changes in temperature can have a radical impact in voltage.  If temperature increases, voltage drops, while if temperature decreases, voltage increases.

Solar panels with low power or voltage temperature coefficients are extremely desired because they mean that the voltage will be less dependent on ambient temperature values that are extremely variable.

The solar panels with the lowest temperature coefficients of the industry are the HIT modules from Panasonic with a value of 0.258 %/°C. 


Tolerance is another rating value of solar panels. It is referred to variations in power output due to manufacturing differences that could lead to less or more power than its nominal power rating. Older solar panels established variations on tolerance from negative values to positive values. Eventually, developers realized that solar panel’s power output was within the tolerance range but generally closer to the negative values.

This reduced the performance of the PV array and created disagreement and unpleasant experiences for developers in large-scale projects where the effect of tolerance is more important. Some people believed that solar panel manufacturers deceived developers in the power outputs of their modules which put at risk the confidence in the industry.

Therefore, today solar panel manufacturers must establish their tolerance value from 0% to a positive number. That way if the power output varies in the tolerance range, it will only imply a positive addition to the PV array.

Tiering System

Finally, there is another rating by solar panel manufacturers that is not related to the technical characteristics but to the economics of the company that manufactures the modules.

The tiering system is a list of the most reliable and financially stable solar panel manufacturers in the world. The list is very important for developers who wish to install a large PV system and may need funding from banks to install the solar power plant. This is also a key factor when deciding whether or not solar panels will pay for themselves over time.

If the solar panel selected for the power plant belongs to a brand that is included in the list (like Trina Solar), then there are higher probabilities that the bank will provide funding for the project because the quality, bankability, (useful for claiming warranty) and manufacturing process of the company have been verified to guarantee that the modules will perform perfectly over the 25 years of the power plant.

Some financial entities like Navigant Research create their own Tier 1 list, however, the only reliable and commonly accepted list comes from Bloomberg New Energy Finance, and it is not cheap. For homeowners, it makes no sense to purchase the list, but for a developer, it may be crucial and may be worth the investment.


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the efficiency bar rating by the side of a house with solar panels

20 Most Efficient Solar Panels in 2020

The 20 Most Efficient Solar Panels in 2022


Written by qualified solar engineer Carlos. Last updated:

Information Updated on 03/17/2020

Solar panel efficiency is one of the most important parameters when you are considering to install a PV system. This factor is not only a reference of quality between a premium solar panel and an average module, but it is also a parameter that defines how much energy can be produced.

The solar industry is constantly changing, therefore, finding the latest updates in the efficiency values of solar panels is not always easy. Here we will show you the most updated ranking of the best brands in 2022, along with their most efficient models. Moreover, we will also learn about solar panel types and the factors that influence the efficiency rating that appears on the datasheet of your module.

Given the importance of this parameter, solar panel manufacturers have focused on increasing the efficiency rating of PV modules. These efforts have driven investments on commercial and utility-scale solar power plants as never before. Regarding the residential sector, solar systems have become more affordable than ever, and energy yields from solar panels are now more attractive for the average homeowner. Here we will address this crucial topic to guide you through the latest releases on the solar industry and the most efficient solar panels in 2022.

The Most Efficient Solar Panels in 2022: The Top 5

Here are the most efficient solar panels in 2022 ranked based on the efficiency of the product:

  1. X series : SPR-X22-370 by SunPower (22.70%)
  2. REC Alpha Series 380 AA by REC Solar (21.70%)
  3. JKM475M by Jinko Solar (21.16%)
  4. HiDM-345MS by Canadian Solar (20.46%)
  5. N340 HIT + Series by Panasonic (20.30%)

The Top 20 Table

1SunPowerX series : SPR-X22-37022.70%
2LGLG Neon R Ace LG380A1C-V5 22.00%
3REC SolarREC Alpha Series 380 AA21.70%
4Risen EnergyRSM144-6-435BHDG21.40%
5JinkoSolarTiger JKM470M20.93%
6CSUNCSP16-72H 20.68%
7AxitecAXI Premium X HC AC-415MH/144S20.63%
8Phono SolarNova Module 72-cell PS400M-24/TM20.61%
11Vikram SolarSomera P-Duplex Half-Cell 144 VSMDHT.72.420.0520.60%

JNMM 144-450

13SolariaPowerXT – 370R-PD20.5%
14BisolBisol XL Series 400W20.5%
15HelieneHeliene 72MH1 Mono 400W20.47%
16Canadian SolarHiDM-345MS20.46%
18Trina Solar144 Half-Cut TALLMAX TSM-DE15M20.40%
20PanasonicN340 HIT + Series20.30%

There are lots of solar panels, but in this comparison table, we show only the best brands in 2022 with the most updated information corresponding to their highest efficiency values.

What You Need to Know

Simply put, solar panel efficiency is referred to the ratio of peak power compared to the amount of sunlight that arrives at the solar cells of the module. In other words, the efficiency value that we can find on the datasheet of a solar panel represents the ability of the module to convert sunlight into electricity according to its size.

Choosing the most efficient solar panels guarantees that your PV system will have an outstanding performance because the best manufacturers produce the highest efficiency values of the solar industry.

The Brands That Perform Well

Here is a brief overview of the best solar panel manufacturers in 2022:

SunPower: American company based in Silicon Valley with over 40 years of experience, 18 million MWh generated from solar energy spread in installations all over the world, and with over 750 patents. Sunpower modules are the most efficient of the industry, and the highest efficiency solar panel of the brand is X series: SPR-X22-370.

RECSolar: Norwegian brand founded in 1996 with over 34 million solar panels manufactured worldwide and with over 8.7 gigawatts produced and powering nearly 17 million people’s homes. Their most efficient solar panel is the REC Alpha Series 380 AA.

JinkoSolar: The Chinese giant of photovoltaic modules in the solar industry was founded in 2006 and has a capacity over 10.8 GW that have been manufactured in their production facilities. The company has over 12,000 employees and has over 15 overseas subsidiaries in Japan, Korea, Singapore, India, Germany and other countries. Their most efficient solar panel to date is the Tiger JKM475M.

LG: International South Korean brand dedicated to the electronics industry with over $56 billion in sales and offices in 119 countries. Began operations related to the solar industry in 1985, and since then has innovated not only in solar panels manufacturing but also in energy storage solutions. Their best solar panel is the LG NeON R – LG360Q1C-A5 model.

Canadian Solar: Canadian company based in Ontario, Canada since 2001with successful business subsidiaries in 19 countries and in all continents. Is one of the global leaders in solar panel manufacturing with over 13,000 employees worldwide and with manufacturing facilities in China, Brazil and South East Asian countries. Their top solar panel is the HiDM-345MS.

The Price Premium

There are scenarios where high efficiency is crucial and others where it is not.

The available roof space and the estimated load for your household will determine if you need to purchase the most efficient modules. Sometimes, the price premium for a high-efficiency solar panel may be worth it. For instance, if you are considering to buy portable solar panels, then high efficiency values are critical because of the nature of use. However, in other occasions selecting premium models might just end up increasing the cost of your PV system unnecessarily.

To find the right answer, request several free quotes to different solar installers, some with high-efficiency solar panels and others with conventional modules. They will include the cost of the system, the energy yields, and the savings per year in their feasibility report. Based on several reports, you will be able to choose the solar panels that better suit your needs and budget.

Commercially Available Values of Efficiency

There are different types of solar panels that, depending on the solar technology, deeply influence the efficiency values. Crystalline silicon solar cells are conventional technology in the industry and these, can be at the same time divided into two main types: polycrystalline and monocrystalline.

Monocrystalline solar panels have the highest efficiency values of the market with ratings varying between 15-22.2% and a lifespan of 25-30 years. Iconic solar panel manufacturers of monocrystalline technologies are SunPower, LG, and JinkoSolar.

On the other hand, polycrystalline solar panels have average efficiency values between 12% and 18% and a lifespan of 23-27 years. Remarkable panel manufacturers of this technology are GCL, Trina Solar and Kyocera.

Thin-Film is the least efficient technology on the market (also called amorphous), and it is developed with a broader range of technologies apart from silicon like Cadmium-Telluride and CIS solar cells. The big advantage of these solar panels is related to flexibility and low weight. Regarding their efficiency range, is generally located between 9 – 14%. Iconic manufacturers are First Solar, Sharp, and Solar Frontier.

Why Should You Care About Solar Panel Efficiency?

The efficiency value is directly related to the power rating and the size of the solar panel. Let’s imagine we have a panel with a specific size and power output. If we increase the efficiency, then it means the panel will need less space to produce the same amount of power. In other words, the module will have the same size, but its power output will be bigger.

On the other hand, if we reduce the efficiency of the solar panel, then it means that the PV system will need to cover more space since the solar panel will have the same size but will have a lower power output. Therefore, selecting the appropriate panel model according to the efficiency rating can have a significant impact on the power output of your PV system, drive important space reductions and, increase annual energy yields.

What Factors Affect Solar Panel Efficiency?

Just how efficient are solar panels and what factors determine the efficiency of a solar panel? Multiple factors can affect the efficiency of solar panels. Maybe one of the most important is the fill factor (FF). This is parameter defines the shape of the I-V characteristic curve of a solar cell and is generally associated with the quality of a solar cell. FF is generally represented as the equation below:

FF represented as a formula and graph

Above we can see a picture of the I/V characteristic curve of a solar cell where 3 points can be highlighted. The Voc, which represents the open circuit voltage (maximum possible voltage of the cell), Isc, which represents short-circuit current (maximum possible current of the solar cell) and MPP, which is the maximum power point of the curve.

The FF represents how square the I/V curve is. In other words, it represents how close is the MPP to the multiplication of Voc and Isc which is the theoretical maximum power that the solar panel can withstand. If the FF is bigger, then the cell efficiency is bigger.

Another crucial factor that influences solar cell efficiency values is quantum efficiency.

Sunlight is composed of small particles known as photons. When these particles impact the surface of the solar cell, they release electrons in the silicon doped structure that allow generating a current flow, and therefore electricity.

The quantum efficiency is referred to the number of photons that are effectively converted into electricity. Companies try to increase this efficiency by applying different solar technologies like PERC, HIT, or IBC solar cells.


We have examined some of the most amazing solar panels and brands with the highest efficiency values of the industry. We have also discussed the factors that influence the cell efficiency and the average values according to the types of solar panels. It is important to notice that there is a degradation in solar panel efficiency over time due to ageing and other factors. To find out the estimated degradation over time for your specific model, you need to look for the performance warranty in the datasheet of the module.

We find out that SunPower solar panels are still the most efficient, followed by LG and Panasonic. The highest commercially available efficiency value has exceeded 22% to the date of writing.

As new technologies are developed, and market competition keeps increasing, we will surely see new breaking records in 2022. Only time will show us their differences.

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