So you found a solar panel that looks nice, opened the datasheet to learn more — and it feels like it’s written in Greek. You don’t need an engineering degree to understand it though. In this article, we'll break down a typical solar panel datasheet, so you can confidently choose the best model for your needs.
The best way to get familiar with solar datasheets is to read one. Let’s pick a panel and look through its specs. We’ll be going with our customers’ favorite Q CELLS Q.PEAK DUO 400 W solar panel. You can download the datasheet to follow along.
The first page of the datasheet usually contains the name of a panel, power output, a photo, and a short description of a panel or its qualities. It is aimed at an ordinary customer without technical proficiency.
Sometimes the first page has information about the warranty, certification and preferable application that we’ll discuss further. Some brands add a little “about us” section and contact details. Some skip the first page altogether and jump right into technical details.
The second page is where things get serious and lots of terrifying numbers appear. Let’s look at each section and figure out what they are all about.
With the Q CELLS datasheet, we start out in the mechanical specifications section. Most fields are self-evident: size, weight, thickness and material of a front cover, backsheet and frame. Cells are where it gets interesting.
Mono and polycrystalline cells are the most common types of cells used in solar panels. Polycrystalline cells are made from multiple silicon crystals, while mono cells are made from a single silicon crystal. Mono cells are more efficient and produce more power than polycrystalline cells but they are also more expensive. Polycrystalline cells, on the other hand, are less expensive but slightly less efficient.
Unique cell designs help engineers increase the efficiency of their panels and improve performance in certain conditions. Here are a few notable examples:
PERC cells, or Passivated Emitter and Rear Cell, are a more advanced type of mono cell. They have a special coating that helps to reduce the loss of electrons and increase the efficiency of the cell in low-light conditions. HJT or Heterojunction cells are made using a combination of amorphous and crystalline silicon layers. They lose less energy at high temperatures. HJT cells are typically used in high-end solar panels, such as Panasonic, REC or Meyer Burger PV modules Bifacial cells are designed to capture light from both sides of the panel. They can produce up to 30% more power than traditional cells. Shingled design is achieved by slicing solar cells into shingles and laying them together to create an electrical connection. Shingled solar panels are better-looking and more durable. They also fight shading 40% better than modules made of cells. This is how Sunpower, Hyundai and Solaria like to design their panels. Half-cut cells are what you get by splitting standard cells with a laser in half. This design lowers power losses and increases the durability of cells and shading resistance. Half-cut cell design doubles the number of cells. That’s why a 120-cell panel with half-cut cells is the same size as a 60-cell one. Check out our article “Strength in numbers: How half-cut solar cells conquer the market” to learn more. N-type cells are silicon cells doped with phosphorus as opposed to more common p-type cells that are doped with boron. N-type cells lose less production in the first year of operation. Read more about them in our article: “N-type vs P-type solar cells: What are these?”
The quantity of cells hints at the supposed application. The 60/120 and 66/132-cell panels are more common in residential installations. The 72/144-cell panels and larger tend to be used in commercial and industrial projects. The line is blurry though: lately, people pick high-output models even for residential systems more often. You can put on your roof whatever you like as long as there is enough space for it. Keep in mind though that 72/144-cell panels and larger are flimsier than standard home solar and don’t withstand harsh weather as well.
Our Q CELLS panel has 132 monocrystalline cells. Q.ANTUM is the brand’s proprietary solar cell technology, but it is based on and very similar to PERC.
The junction box serves as a connection point for electrical components within the panel. Its primary function is to protect the wiring and connections from elements. An IP67 rating means that the device is protected against dust and water jets from any direction.
IP code or ingress protection code indicates how well a device is protected against water and dust. The first digit stands for protection against solid (0-6) and the second one represents protection against moisture (0-9)
The junction box has bypass diodes and the datasheet often mentions them. Bypass diodes split the module into independent sectors and increase its shading tolerance. If a solar cell in one of the sectors gets shaded, a bypass diode doesn't allow it to influence cells in other sectors. Solar panels have 2-4 bypass diodes.
Connectors that are compatible with your panel are listed at the end of this section. Generally, most solar panels employ MC4 connectors. You can see that connectors also have an IP rating.
Electrical specifications are the most important part of the datasheet. This is where you can find the voltage, current and expected power output of the solar panel.
The power class is a way to classify the variations of the same model based on their wattage or power rating. Solar panels within the same power class are designed to have similar power output characteristics, efficiency levels, and electrical performance.
The rated power output of a solar panel is measured in watts (W) and indicates the amount of electricity that the panel can produce under standard test conditions. With enough sunlight, that number is what the panel will be generating.
P MPP = I MPP × V MPP
Power at MPP equals current at MPP times voltage at MPP
MPP stands for Maximum Power Point. It’s the combination of voltage and current at which the solar panel delivers the highest electrical power.
Solar panels have a characteristic called the current-voltage (IV) curve, which represents the relationship between the voltage across the panel and the current flowing through it. This curve varies depending on factors such as temperature, shading, and the amount of sunlight received.
Power tolerance defines the range of power output that a solar panel is expected to deliver under normal operating conditions. Tighter power tolerance means smaller variability and higher quality of a panel.
Tolerance can be expressed as a number or as a percentage of the panel's rated power output. For example, if a panel has a rated power output of 300 W and a power tolerance of +/- 3%, then the panel could deliver between 291 and 309 W of power under normal operating conditions.
The Q CELLS panel we’re examining has a tight power tolerance — just 5 W. Even more important, this power tolerance is positive. This means that your panel’s output can be up to 5 W higher than promised but not lower.
The voltage is measured in Volts (V). It’s the force that pushes the electricity through the wires from the panel to the electrical loads or to a battery or inverter. Think of it as the pressure that pushes the water through a hose. The voltage at maximum power (Vmp) represents the voltage output of a solar panel when it is operating at its fullest capacity.
If voltage is like pressure in the pipes, then current is like water. It's measured in amperes (A) and represents how much electricity is flowing at a given moment. Current at maximum power (Imp) represents the current output of a solar panel when it is operating at its fullest capacity.
The short circuit current (Isc) of a solar panel refers to the maximum current that the panel can generate when its output terminals are short-circuited. In other words, it is the current that flows through the circuit when there is no external load connected to the panel.
When the output terminals of this 400 W solar panel are short-circuited, it can produce a maximum current of 11.14 A. If you were to connect an ammeter directly across the positive and negative terminals of the solar panel, that’s how much it could show when the panel is operating under standard test conditions.
Similarly, the open circuit voltage (Voc) of a solar panel refers to the voltage across its terminals when there is no external load or current flowing through it. In other words, it is the maximum voltage that the solar panel can produce when it is not connected to any electrical device or circuit.
Voc and Ioc represent the highest the current and voltage can get. These are useful numbers to know when you pick equipment for your system. Controllers, inverters, and batteries have maximum input voltage levels which should not be exceeded.
Connecting your solar panels in series makes their voltage outputs add up. Wiring PV modules in parallel increases current while voltage stays the same. You can choose whether to increase volts or amperes in your system by trying different configurations and combining them.
For longer distances between the solar panels and the inverter or battery, a higher voltage system can be more efficient. With higher voltage, the same amount of power can be transmitted over a longer distance with less voltage drop and a smaller wire size. This can save on wiring costs and reduce energy losses. Home solar arrays usually feature series connection.
For shorter distances, a higher current system can be more efficient. With a higher current, less voltage drop occurs in the wires, and larger wire sizes don’t increase costs too much due to short distances. RV and boat arrays often employ parallel connection.
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Efficiency refers to the percentage of sunlight that a panel converts into electricity. The more efficient a panel, the smaller it needs to be to generate a given output. This number becomes important if you have limited space and energy needs are large. Here’s how it is calculated:
Efficiency = [Power output / (Area of panel x 1000 W/m²)] x 100%
The most efficient home solar panels are just shy of a 23% conversion rate. The average efficiency number is closer to 19-20%. Monocrystalline panels are more efficient than polycrystalline ones which explains why polypanels slowly go away.
Some datasheets include a curve that represents the relationship between efficiency and irradiance levels. A sunny day can provide irradiance levels ranging from 800 W/m² to 1000 W/m² or even higher. The exact irradiance levels fluctuate throughout the day because of the sun's position and atmospheric conditions.
Manufacturers write down the performance numbers that they obtain under Standard Test Conditions (STC). They include 77°F cell temperature, 1000 W/m² of irradiance and an Air Mass of 1.5 AM. They look good on paper and they stay on paper: you usually don’t get these conditions that often in the real world.
Normal Operating Conditions (NOCT) recreate real-world environments more faithfully. NOCT are air temperature of 20°C, 800 W/m² irradiance, air mass of 1.5 AM and 1 m/s wind speed. This rating gives a better indication of how a panel will actually perform but not every manufacturer writes it down in the datasheet.
When comparing panels, it's better to look at their NOCT ratings rather than their STC ratings. Let’s say panel A has an STC rating of 300 W and a NOCT rating of 270 W while panel B has an STC rating of 290 W and a NOCT rating of 280 W. Panel B will perform better in real-world conditions, despite having a lower nameplate capacity. You can learn more in our article “Understanding solar panel output: Standard Test Conditions vs. Real world”.
This specification measures how much the panel's efficiency drops as its temperature rises above 77°F. Panels with lower temperature coefficients are more efficient in hotter climates. In particular, solar panels with HJT resist heat better.
10%
average power losses of a solar panel on a hot summer day
Let’s say you see a temperature coefficient of 0.36% in a datasheet. This would mean that for every 1.8°F above 77°F, your panels would lose 0.36% of performance. Keep in mind that solar panels get much hotter than the ambient temperature. In particularly hot climates, PV modules can reach temperatures of up to 150°F, meaning almost 15% of performance loss.
When looking at the temperature coefficients block, we’re interested in the temperature coefficient of power (P), because it represents the drop in performance as temperature rises. The Q CELLS panel we picked would lose 0.34% of the performance for every 1.8°F above 77°F, which is slightly better than average.
Nominal Module Operating Temperature (NMOT) represents the temperature that solar cells reach in a module under 800 W/m² irradiance, air temperature of 68 °F, 1 m/s wind and open backside mounting. Generally, an NMOT or NOCT — Nominal Operating Cell Temperature — varies around 113 °F. The lower NMOT the better. There are situations when even though the temperature coefficient of a panel is high, it loses less power on hot days because of low NMOT.
0.7%
average annual degradation rate of a solar panel
Every solar panel has a product warranty and a performance warranty.
The product warranty covers any defects or issues with the actual panels. It typically lasts between 10 and 25 years, depending on the manufacturer. The highest it gets is 40 years with some of SunPower's solar panels. Our Q CELLS panel has a 25-year product warranty, according to the first page of the datasheet.
The performance warranty guarantees that the panels will produce a certain amount of power for a specified number of years. Performance warranty almost always lasts for at least 25 years. Bifacial panels often get a 30-year output warranty. We can see that Q CELLS promised that their panel will retain at least 93.5% after 10 years and 86% after 25 years.
This section helps installers when they set up the solar array and connect it to the grid. It contains data on the durability and fire safety of a solar panel.
The maximum system voltage (MSV) refers to the highest voltage that the system can handle safely. Exceeding the maximum system voltage can lead to electrical hazards, insulation breakdown, component damage, or even fire risks.
To calculate the MSV, you need to consider the highest voltage that the system can reach, taking into account the solar panel voltage and the inverter's input voltage rating.
Q CELLS 400 W solar panels have a Voc of 45.3 V, which is the maximum voltage that can be generated by a single panel. When panels are connected in series, their voltages add up.
Let's say you have 10 Q CELLS panels connected in series and an inverter with a maximum input voltage of 500 V. The total voltage of the array would be 45.3 V * 10 = 453 volts. In this scenario, the MSV would be determined by the highest voltage in the system, which is the maximum voltage of the inverter, rated at 500 volts.
Solar panels are often connected in series to increase the voltage. To protect the wiring and components in the event of an overcurrent situation or fault, you can install a series fuse within the circuit. The Maximum Series Fuse Rating refers to the maximum rated current that it should have.
With a Maximum Series Fuse Rating of 20, the recommended or maximum rated current of the fuse should not exceed 20 amperes. Using a fuse with a higher current rating could compromise the protection and safety of the module. A fuse with a lower current rating may blow prematurely and disrupt the system's operation.
The maximum load of a panel represents the durability of a module. Sometimes the manufacturer defines the design and test load of a panel. He can also specify the maximum front load and rear load of a panel.
The design load represents what the solar panel is expected to withstand at normal operating conditions. The test load is a higher-than-design load applied during testing to verify the panel's performance and safety under extreme or abnormal conditions.
Front load is a measure of how much pressure a panel can handle from the front, typically from wind or snow loads. Rear load is a measure of how much pressure a panel can withstand from the back, typically from the wind. The load rating is measured in Pascals (Pa) which is a unit of pressure.
Our Q CELLS panel has a design load of 3600 Pa. This is comparable to a 170 mph wind. The panel is designed to withstand hurricanes up to the highest Category 5 on Saffir-Simpson wind scale.
"Class II" refers to an electrical safety classification of a PV module. It signifies that the module is designed and certified as a "double-insulated" or "reinforced insulation" product. The classification is based on the International Electrotechnical Commission (IEC) standard IEC 62109-1, which provides safety requirements for PV power conversion equipment.
There are also Class I and Class III of PV modules: Class I panels are classified as "earthed" or "grounded" products. They require a connection to the earth or ground for safety purposes. Class I modules have exposed conductive parts that can cause electric shock if touched, and they rely on a ground connection to divert any fault currents. This class of modules typically requires additional safety measures, such as grounding systems, to ensure proper electrical safety. Class III PV modules are classified as "safety extra-low voltage (SELV)" products. They operate at voltages below 50 V AC or 120 V DC and have an inherently safe voltage level. These modules are designed to eliminate the risk of electric shock. They are often used in areas where the risk of electrical hazards needs to be minimized.
The Fire Rating based on ANSI/UL 61730 refers to the module's classification and compliance with fire safety standards set by the American National Standards Institute (ANSI) and Underwriters Laboratories (UL).
The Type 2 classification indicates that the PV module has undergone fire testing and meets the required criteria for fire safety within the ANSI/UL 61730 standard. Although it doesn't offer the highest level of fire resistance of Type 1 or Class A, it still demonstrates a satisfactory level of fire performance.
IEC — International Electrotechnical Commission is international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies
Certifications are one of the ways to independently verify some of the manufacturers’ claims about their solar panels. Certificates are granted by independent entities. Their businesses are entirely dependent on their fair judgment and sound reputation, which makes them worthy of trust. Below are a few certifications you may encounter in a typical solar panel spec sheet.
IEC 61215 and IEC/UL 61730: These are international standards for testing and certifying the performance and safety of solar panels. They cover a range of tests such as thermal cycling, hail impact, and resistance to wind and snow loads.
UL 1703: This is a certification for solar panels that is widely recognized in North America. It includes tests for electrical safety and fire resistance.
UL — Underwriters Laboratories is a global safety science company headquartered in Northbrook, Illinois which delivers testing, inspection and certification services
TÜV Rheinland: This is a German certification organization that provides a range of testing and certification services for solar panels. Some examples include PID resistance, ammonia resistance, and salt mist corrosion resistance.
CEC (California Energy Commission) certification: This is a certification required for all solar panels sold in California. It includes tests for performance and durability, and panels must meet certain efficiency standards to be eligible for incentives in California.
Energy Star: This is a voluntary certification program that sets energy efficiency standards for a range of consumer products, including solar panels. Energy Star-certified solar panels must meet certain efficiency and reliability criteria to earn the certification.
CE-compliant. CE mark shows that the product is safe for people and may be traded freely in any part of the European Union
Our Q CELLS solar panel has all the important certifications, as well as an ongoing QCPV process. This certification program requires the presence of independent TÜV Rheinland experts at production sites/module testing locations. This is a sign that the data provided in the spec sheet is reliable.
In the final section of the datasheet, Q CELLS specifies how exactly the panels are to be packaged and transported. What you might be interested in here is the size of a pallet. Notice that it is slightly larger than a panel. If you decide to pick up the products yourself and choose ‘palletized order’, make sure that the pallet fits into the pack of your car.
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Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.
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Writing for electronics manufacturers like Bitmain taught Maxim to extract the important details from lengthy equipment documentation. At the same time, it made him aware of the environmental effects, and he put his talents to work for a renewable future.
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