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How to Read A Solar Panel Spec Sheet

Every solar panel comes with a specification sheet pasted onto its backsheet by the manufacturer. The spec sheet often contains valuable information about the operating parameters of the panel. Its tells much about the panel's electricity production capacity, its ratings, information about the control tests it had passed before being introduced into the market and other information that relates to how it operates under changing temperatures. It also contains information unrelated to the electricity production capabilities of the panel like the dimensions of the panel and its wind load.


The information on the spec sheet gives power system designers, installers and users enough information with which they can simulate the performance of the panel in the configuration of the electricity system of which they form its major components. These specifications are stated in the spec sheet as given 'at standard test conditions (STC)'. In general, an STC has the solar cell at 25℃, with the sunlight intensity at 1,000W/m2 (about the intensity of the sun at noon), and the air mass (AM) is 1.5. Standard test conditions do not however reflect typical operating conditions because full-sun cell temperatures tend to be much higher than 25°C.


In addition to the logo of the manufacturer, and the type name locating the panel in the manufacturer's series, type or range of panels, the spec sheet of every solar panel will most likely contain the following:


Maximum Power/Peak Power (Pmax)

Maximum power, peak power or maximum point power is the wattage of the panel or the amount of power it is expected to generate. Typically, solar panels are rated between 250 and 400W. Since 2020, power panels with power point ratings above 400W are being issued by the top manufacturers. These high power panels, expected to become the staple of the industry in a few years, take up lesser space while giving more power.


Maximum Voltage (Vmax,)/Voltage at Pmax (Vmp)/Maximum Power Point Voltage (Vmpp)

This is the voltage when the power output is the greatest. It is the voltage that registers on the inverter or the charge controller under standard test conditions.



Maximum Power Current (Imp)/Maximum Point Current (Impp)

This gives the current of the panel when it is producing at its peak. It is the actual amperage that one is to expect to see when the panel is connected to a charge controller under standard test conditions.


Short Circuit Current (Isc)

The Isc is the highest current the solar panels will produce under standard test conditions. The Isc gives the value of how much current the solar panel can produce when not connected to a load but when the terminals of panels wires are directly connected to each other. It can be gotten with an ammeter across the terminals of the panel.


Open Circuit Voltage (Voc)

The Voc of the panel gives the value, in volts, of the solar panel's output with no load on it. It can be gotten with an voltmeter across the terminals of the panel. It is a very important information, as it is the maximum voltage that the solar panel can produce under standard test conditions. This is the number to use when determining how many solar panels that can be connected in series going into the inverter or charge controller.


Number of Cells

A spec sheet may give information as to the number of cells that make up the module. Traditionally, most panels contain 60-72 cells but new technologies have increased the number of cells that can be connected together into one module.


Application Class

The application class tells what purpose the manufacturer intends the module to be used for. There are three classes of applications: class A for buildings, class B for large-scale utility in very remote places and energy retailer or supplier applications and class C for low-voltage applications.


Operating Temperature

The operating temperature of a solar panel is the temperature range under which the solar panel device can operate without being damaged.


Fire Rating

Fire Rating refers to a fire-resistance rating system for the roof covering materials based on their ability to withstand fire exposure. This standard includes three classes of fire protection levels, according to the fire source exposure:


• Class A roof coverings, which are effective against severe fire test exposures;

• Class B roof coverings, which are effective against moderate fire test exposures;

• Class C roof coverings, which are effective against light fire test exposures.


Most solar panels are rated Class A.


Qualifications and Certificates

In the solar panel datasheet is also to be found above, below or besides the specification of the panel, certificates showing that the manufacturers have had their product independently tested and found to be in conformity to certain test conditions and industry standards.


All solar modules must be VDE-conform, certified in accordance with both IEC61215 and IEC61730, and should feature the CE-sign. The CE (Conformité Européenne) sign is an administrative marking that indicates that a product or service conforms with health, safety, and environmental protection standards for products sold within the European Economic Area. It is also found on products sold outside the EEA that have been manufactured to EEA standards.


The best modules always contain the TUV and IEC signs.

All electrical appliances include safety warnings about electrocution. The spec sheets of all solar panels include a warning that they may be hazardous when exposed to sunlight. Spec sheets are a very important part of a solar panel. Any solar panel without a spec sheet or with typographical errors, ineligible lettering or bubbles in the spec sheet and spec sheets that have peeled off point to a substandard manufacture or a counterfeit.


In other cases, the spec sheet may also include the following: the weight of the panel, a serial number, barcode, nominal voltage etc. The nominal voltage of a panel is not always specified. But the nominal voltage of a panel tells what battery voltage is to charge it. It is not a real voltage that can be measured, rather it is a category in which the manufacturer places the panel.


SolarKobo helps its clients in Lagos and elsewhere in Nigeria make the best possible choice of solar panels and other solar electricity products. We also have university-trained engineers that provide high-grade installation services on order.

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