How to Read Solar Panels Specification

A quick glance at a solar panel’s specification sheet will reveal the power generation and conversion efficiency of a system. If you don’t know what the numbers mean, it may as well be written in another language. Unless you want to fall for a solar panel scam or get a system that doesn’t deliver the ROI you expect, it’s time to brush up.

Understanding solar panel specs is critical for comparing different systems. So what do all the numbers mean, and how do you decide which ones matter for you? Let’s take a closer look.

Standard Testing Conditions

Before we deep-dive into solar panels specifications, it’s important to understand that all of these panels are tested in standardized conditions. That makes it easy for a lab to test panels for comparison to other systems – and for you to compare panels.

These laboratory conditions include a solar cell operating condition of 25°C (77°F), solar irradiance of 1000 watts per square meter, and an air mass of 1.5. 

However, environmental factors in the real world mean your panels must be suited for a range of conditions. 

There are many things that can affect the efficiency of solar systems, such as: 

  • Angle of installation
  • Temperature
  • Humidity

That means power output can vary from day to day, and even hour to hour. It’s why you should always consult with experienced solar energy professionals to make sure your system delivers the power output you require for your home or business. 

Which Solar Panels’ Specs Matter Most?

Sizing your system is one of the most important aspects of your purchase. You’ll need to meet your energy requirements in available space to get the best value for your system. 

The solar panel specification sheet gives you all the information including physical dimensions and the power rating.

For instance, if you live in a place where tornadoes or hurricanes are common, you want to take into account the static wind loads of different solar panels. Or if you are based in an area that experiences high temperatures, consider investing in solar panels with the lowest temperature coefficient.

Solar panel specifications help you make an apples-to-apples comparison between different systems. Solar energy can be a long-term commitment, which is why it’s worthwhile to slow down and compare the specs of any system you’re considering. 

If a salesman is pressuring you for a purchase without letting you review the technical information, it’s a major red flag

It also helps to look beyond the spec sheet. If your solar energy company offers a long warranty and maintenance, it can save you a lot of hassle.

Solar Panel Specifications Explained

How to Read Solar Panels Specification


Solar panels are rated with a variety of indicators for efficiency. Here’s an explanation of some of the more important specifications.

1- Maximum Power Point (Pmax)

What is Pmax? Maximum power point, or Pmax, describes the maximum wattage a panel can generate under ideal conditions. You can multiply this by the number of panels to get a system’s maximum power output. For instance, a system with 5 x 100-watt panels has a Pmax of 500 watts. 

Some solar panel spec sheets may also list a panel’s PTC rating. Unlike Pmax, which is determined under lab conditions, PTC represents performance under real-world conditions. 

Note that ratings are not perfect and the electricity you generate can vary depending on the environmental conditions in your area. In order to get the most from your investment, you’ll want to install a system that can consistently generate enough energy to eliminate your monthly bill. 

Your solar installer can help you determine how to meet your energy needs based on your electricity bill. 

2- Power Tolerance 

Power tolerance is directly related to your system’s Pmax. It describes the amount of energy your system can produce above or below the rated maximum. It is either listed in watts, or as a percentage of the total output. So a panel rated at 100 watts with a power tolerance of +/- 3 can produce between 97-103 watts. 

These small variations may not seem like a big deal. However, when the cells on an array are constantly running different volts and amps, you can lose efficiency. 

It can also increase the rate of panel degradation. That means power tolerance is also a sign of reliability: the lower the rating the longer a panel should perform at its peak performance. 

3- Weather Ratings

Most solar panels have a static wind rating and a static snow rating. These ratings help you understand how durable they are under extreme weather conditions. Some heavy-duty panels are designed for harsh weather, and they are worth considering if you live in an area that experiences heavy storms.

The static wind load describes how much force the cells can withstand once they are mounted on your roof. This is measured in Pascals or pounds of pressure per square foot. 

Typical solar panels have a static wind load rating of 2,400 Pascals, or 50 lbs per square foot. That translates into up to 141 mph of wind before there is risk of damage.

Static snow load measures how much weight solar cells can be placed under before they get damaged. The average solar panel has a static snow rating of 5,000 Pascals. That translates to around 2-4 feet of snow, depending on how densely packed it is. 

4- Temperature coefficients (PMPP)

As we mentioned above, lab conditions are rarely encountered on a roof. It’s why one of the solar cell specs used is temperature coefficient, or PMPP, describing how higher temperatures can affect your system’s power output. 

The PMPP rating is given as a percentage per degree of temperature increase.  

Your solar specs will list this as the Temperature Coefficient of PM. A temperature coefficient of .41% / °C means you’ll lose .41% of your output for every degree above 25°C (77°F), the standard testing temperature. 

If you regularly experience temperatures above 100°F, it’s possible your panels reach temperatures of up to 149°F. It’s why lower PMPP solar panels are ideal if you live in a hot climate. 

5- Open Circuit Voltage (VOC) 

Which Solar Panels’ Specs Matter Most?

This reading describes the maximum voltage a solar panel can produce on a circuit without resistance. It’s measured with an amp meter on a solar panel before it’s hooked up to your system.

The solar panel’s VOC electrical rating is important to know for compatibility purposes during installation. If it’s not in the acceptable range of your solar charge controller, you’ll run into issues down the line. 

6- Short Circuit Current (ISC)

A solar panel’s ISC rating describes how much current flows through the wires when the voltage is at zero. 

If the circuit between the two wires coming out of the solar panel was completed, this is how much current would flow through them (do not attempt this yourself, it can damage your system and cause serious injury). 

This number is primarily included to make sure you are using wiring and fuses with a rating strong enough for the system. For the ideal installation, it should also perfectly match the light-generated current. 

7- Dimensions

The dimensions listed on solar panel labels refer to the size of each solar cell. For most people, this is the easiest number to understand. The dimensions will show you the area each cell covers as well as how thick they are. 

Knowing the dimensions of the panel will give you an idea of how much space you need for the system. If a solar system is too big for your roof space, then you will need to find smaller, higher-efficiency panels to generate electricity. 

Common questions about solar power:


Go Solar With Airis

Understanding and comparing the specs for your system takes diligence. Finding a trustworthy installer that can help you find what you need makes all the difference for your investment. 

When you book your free evaluation, a solar expert will assess your premises and recommend the right system. You can start saving up to 100% of your electricity bill from day 1 itself. 

At Airis Energy, we make going solar completely turnkey. We provide preventive maintenance and servicing for 20 years at no additional cost, which means you never have to worry about unexpected costs.

We make going solar easy!

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