s solar energy increasingly becomes a focal point in discussions about sustainable living, understanding the performance of a solar system is essential. This article breaks down what you need to know, from wattage to efficiency, and guides you through the calculations and real-world examples. Get ready to be solar-savvy.

Understanding Solar Panel Power Rating and Efficiency

Solar panels come with specific metrics that can sometimes be confusing. One of these metrics is the power rating, often expressed as wattage. It essentially refers to the electrical output that the solar module can produce under standard conditions. While a high-wattage panel indicates greater power, efficiency should not be overlooked, since it determines how well the panel converts sunlight into usable energy. The highest efficiency panels on the market today reach up to 23.6%.

Factors Influencing Solar Panel Performance

Various elements come into play when it comes to photovoltaic (PV) panel performance. Let’s explore the main ones.

Sun Hours VS PV Modules

The average sun hours your location receives is a crucial factor in your solar system’s output. For instance, Arizona receives approximately 6.57 sun hours per day, offering excellent solar potential. Illinois, however, only averages about 3.14 sun hours per day, meaning you'd likely need more solar modules or higher-efficiency solar modules to generate the same amount of energy.


Contrary to what some may believe, solar systems tend to perform better in cooler conditions. Elevated temperatures can actually reduce a panel's efficiency, meaning that solar systems in hotter climates may not perform to their maximum potential.


Even minor shading can significantly impact a solar panel's performance, affecting the overall solar energy output. While some modern systems come with optimizers to mitigate this issue, it's generally best to install your solar modules in an area free from obstructions like trees or buildings.

Calculating Solar Energy: The Easy Way

While calculations and a handy chart can give precise results, they might appear daunting. So let's create an easier solar panel energy calculator. Imagine you have a 350W solar panel. What does that mean? It means your module is able to produce 300 watts under standard testing conditions. But real life is not a laboratory so how do solar panels perform in real life? Let’s take a look at some calculations.


In Arizona, where the average daily sun exposure is 6.57 hours, a 350W solar module would produce approximately 2,299.5 watt-hours or about 2.3 kWh daily. Over a month, that's about 69 kWh. Keep in mind that this solar power estimate doesn't account for real-world variables like temperature fluctuations, so your actual production might be a bit lower.


In Illinois, the sun shines for an average of 3.14 hours a day. A 350W solar module here would produce around 1,099 watt-hours or roughly 1.1 kWh daily. That amounts to about 33 kWh per month.

The Verdict: Solar Calculations

Clearly, geography plays a pivotal role in solar panel efficiency. As demonstrated through our calculations using a 350W solar panel as an example, the solar potential in Arizona substantially outperforms that of Illinois. Keep in mind that these estimates are somewhat simplified, not accounting for additional variables like temperature and other potential energy losses. Therefore, while the panel's wattage remains constant, its actual output can differ significantly based on various factors.

Final Thoughts

We've peeled back the layers on solar module wattage, efficiency, and how factors like location affect energy output. Using Arizona and Illinois as examples, you can see that identical solar panels can have varying performances due to local conditions. Armed with this understanding, you're now better equipped to grasp the complexities of solar energy.

Sep 26, 2023

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