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Understanding Solar Panel Specs

By Benjamin Strusnik June 16, 2022

The world’s major cities and suburbs have made the sustainable switch to producing electricity. “How?” you may ask. Well, through the use of the sun’s incoming solar rays.

One of the most popular and effective ways to produce energy sustainably is through the use of solar generator systems, as they use a renewable energy source to generate power – the sun.

Switching to solar energy to power your home can be a daunting financial decision to make, especially as a first-time user, but I can assure you that the benefits significantly outweigh the potential drawbacks.

Solar panels not only reduce greenhouse gas emissions but also play an important role in reducing our monthly electricity costs. Over the long term, solar panel systems offer us an increase in our financial savings and a reduction in our carbon footprints, allowing us to live greener lives.

There are so many other benefits associated with having a solar panel installed, that it would be silly not to consider a system for your own home. However, before installing a solar panel, it is important to understand the specifications that are associated with solar panels and how it functions.

The following simple guide will shed light on the main solar panel specifications, as well as touch on how solar panel systems can generate electricity using the sustainable resource that is the sun.

The Most Important Specs

Solar panels come with a sheet list of specifications, and it can be overwhelming to understand it all. Not all these specifications are important to understand fully, as they involve a lot of unnecessary and wordy jargon that is enough to confuse the average buyer.

understanding solar panel specifications

However, there are a few specifications that are essential to solar panel functioning and play an important role when comparing different types of solar panel systems. These specs will help you decide on a panel that is well suited for your home or business.

Watts Love Got to Do with It

One of the most, if not the most, important specifications when it comes to solar panels is the wattage.

The wattage of a solar panel is the electricity that is produced by your solar panel system under standard test conditions, which we will explain later.

When referring to solar panel wattage, it is important to understand that the number you see is not equivalent to real-world testing. Instead, the wattage number refers to testing under controlled laboratory conditions.

In the real world, a solar panel does not have infinite exposure to the sun. A solar panel installed on your roof will only get a few hours of maximum sunlight exposure per day.

Thus, the wattage number you see on your panel specs will never be a true representation of the actual wattage. However, the number is still important, as solar panel systems with higher wattages will produce more electricity per year.

What Are the Standard Test Conditions (stc)

As mentioned above, solar panel systems are certified to perform under strict laboratory conditions, also known as the standard test conditions. All the official specifications have been tested under the STC.

The STC was developed to allow for easy measurement and comparison between solar panels, as it does not involve external factors that might impact the energy output.

reading the specifications of a solar panel

The standard test conditions for solar testing have a strict procedure that involves panel orientation directly to a solar source of 1,000W per square meter.

The temperature of the solar panel is also maintained at 25 degrees Celsius (77 degrees Fahrenheit) when performing these tests. Lastly, the atmospheric mass, which refers to the amount of atmosphere between the panel and the solar source, is kept at a strict 1.5 overhead or 500 feet above sea level.

These specs generated from these standard test conditions do not tell you how well a panel will work in the real world, but it does make for easy comparisons between different solar panel systems.

Why Are the Standard Test Conditions so Strict

Taking a step back from the specifications, it’s important to note that there are a lot of other factors that can impact the power output of your solar panel. This is reasoning the STC is so strict when testing solar panel systems. 

It would be a lot more troublesome and arduous to test solar panel systems in a real-world environment even though solar panels are waterproof and quite durable.

Additionally, if you were to somehow encounter an EMP, then the good news is that there are EMP-proof solar panels if required.

Things that affect your solar panel's power output include heat, orientation, shaded, and dirty panels. Heat, believe it or not, can significantly impact the energy output of a solar system. The hotter a panel the less power it can generate.

Orientation of the panel is also something that the STC took into account. Flat solar panels can significantly reduce the power output compared to panels tilted directly towards the sun.

Having the STC under strict lab conditions allows for the absence of dirt and shade. These two factors are a big concern among solar panel owners. The tiniest bit of dirt or blemish can massively impact the final energy output of your solar system.

specifications of a solar panel

Finally, the time of the day the panel is in contact with the sun is something that the STC considered. There’s only so much sunlight available in a day and a small proportion of the day is the only time a panel can produce the majority of its daily energy output.

The factors mentioned above are the reason for panels being tested under the STC. It allows buyers to compare solar panel systems to one another.

Normal Operating Cell Temperature (NOCT)

Now that we know about the STC, we can look into the normal operating cell temperature, which gives us a real understanding of how your solar panel will perform under real-world conditions.

The NOCT on your solar panel specifications list is close to the truest power rating that you are likely to see from your solar panel system.

Unlike the STC, it uses 800 watts per square meter, instead of the whopping 1,000 watts per square meter. This is the more realistic wattage associated with mostly sunny days and periods of cloud cover.

The temperature also differs slightly. Instead of the 25 degrees Celsius (77 degrees Fahrenheit), the NOCT uses a temperature of 20 degrees Celsius (68 degrees Fahrenheit).

It also incorporates panel wind cooling as you would in the real world. Ultimately, the NOCT ratings will be lower than that of the STC, but these numbers will be more realistic to what your solar system is capable of.

Solar Panel Efficiency

Another specification that you’ll find on the long list of specs is solar panel efficiency. This is an incredibly useful piece of information, and it should not be overlooked by a solar panel buyer.

To put it into simple terms, your solar panel's efficiency is how effective the system is at converting the sun's solar rays into household electricity.

Your solar panel efficiency is dependent on a variety of factors from solar panel size to how many solar cells are in your solar panel. However, the most important factor is the amount of daily sunlight that the solar panel has direct contact with. The amount of sunlight is the primary factor in determining the final output voltage of your solar energy system.

solar panel specs

Your solar efficiency specs are usually given as a percentage. The higher the percentage the more effective your panel is at converting solar to electricity.

To put it into practical perspective, if your solar system has an efficiency of 50%, it ultimately means that 50% of all incoming solar energy is converted to electricity.

Higher solar panel efficiencies are desirable because you require fewer panels for the same energy output, which in turn reduces the weight of solar panels on your roof. This allows you to play around with the available space on your roof or any other area dedicated for panel installation.

The only serious trade-off with high-efficiency panels is that they cost more. However, over the long term, you will notice some serious return on investment.

In general, solar panel efficiency percentages are low, but you should always keep in mind that your system is essentially utilizing free energy input from the sun.

Solar Panel Temperature Coefficient

As mentioned earlier, solar panel efficiency and energy output are dependent on the temperature. The Higher temperatures the less efficient solar panels are at performing their sole function – energy production.

Thankfully, there is a number on our specification data sheets that lets us know about how our solar panel system functions in the heat. This is known as the solar panel temperature coefficient.

The temperature coefficient is measured as a percentage loss per Celsius degree in most solar panel systems.

As an example, let’s say your solar panel has a temperature coefficient of -0.05% per degree Celsius. This would mean that your solar panel would lose 10% productivity with a temperature rise of 20 degrees Celsius.

On the other hand, let’s take a solar panel with a coefficient of -0.26% per degree Celsius. This means that you would only lose 5.2% of the overall productivity with a temperature increase of 20 degrees Celsius.

As you can see, the lower the temperature coefficients, the less overall productivity you will lose. Make sure to take this into account when comparing solar power systems.

specifications of  solar panels

Open Circuit Voltage (Voc)

The open-circuit voltage is an important spec of all solar panel systems. In simple terms, it’s the number that reads on the voltmeter if your solar panel is not connected to any other electrical device.

Voc tells you the maximum voltage a solar panel can ever produce, and it is always higher than the maximum power point voltage (Vmpp), which we will touch on later.

The Voc is measured using STC and it will tell you how many solar panels you can wire in series connected to your inverter or charge controller.

Maximum Power Point Voltage (Vmpp)

The maximum power point voltage is a key number for every solar panel. It’s defined as the voltage when the power output is at its greatest.

This is the voltage you see when your solar panel is hooked up to electrical devices, such as a solar charge controller or inverter under the STC.

Solar Panel Warranties

The warranty of your solar panel should never be overlooked, as it’s a sign of how long the manufacturer expects your solar panel to perform efficiently.

There are two types of warranties associated with solar panels – a product warranty and a power output or performance warranty.

The product warranty is like any normal warranty that you may have on your other items. If any of the solar panels fail or give in prematurely, then the manufacturer will kindly hand you a brand-new replacement.

A standard product warranty is between 10-12 years. However, other solar companies may issue warranties up to 25 years, which is the go-to option in the solar industry.

the most important specs of a solar panel

The power output warranty, also known as the performance warranty, is a guarantee that your solar panel production will continue at a certain efficiency for a certain number of years.

Generally, solar panel production and efficiency are reduced slowly over time and this warranty protects you from the efficiency dropping below a level it shouldn’t. If it does, then you will be issued with a new replacement panel.


There are so many financial and environmental benefits associated with solar energy that it seems like a no-brainer to make the switch. However, it is important to do your homework on solar panel specifications, especially if you stay in an area that doesn’t get a lot of direct sunlight.

It is always good to hone in on specific performance metrics and specs of solar panels before purchasing one for your home.

Solar panels that have higher wattages and efficiency would be first prize, but other fantastic options are available to you if you don’t have the space.

This article has shed some light on solar specifications and helped you understand it in simpler terms devoid of any serious solar jargon. If you are unsure of anything and require further assistance, it is important to consult a solar company.

Shop Solar Kits has a great option on their website which allows you to select the best solar kit for your home. They also offer great customer assistance if you need help with your solar queries.

Now that you’re a solar expert and understand the specs involved in solar panel systems, it’s time to make the sustainable decision and switch to powering your home with solar energy. Mother Nature will thank you.

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