How to Measure the Output of Solar Panels

How to calculate the output of solar panels is a common question from homeowners. This makes sense considering the impact that solar panel production has on the overall system. Exactly how to calculate the power output of solar panels involves a number of variables and steps.

 

Some of the most important factors in calculating solar panel output

▸The efficiency of your solar panels

▸Location (how much sunlight is shining on your solar panel)

▸Which direction your solar panel is facing

Of course, there are other variables that can change the final output number, but the three above are the main contributors.

 

 

How Location and Orientation Affect Solar Panel Output

Where you live and your solar panels

Where you live has a big impact on how much energy your solar panels can produce. That's why solar energy is used first in sunny places.

The more sunlight your solar panels get, the more energy they will produce. While some areas in northern latitudes average less than 4 hours of sunlight per day, other areas can have more than 7.5 hours of sunlight.

Obviously, the more sunlight, the better. But even in northern locations, you can still enjoy the benefits of solar energy.

 

The direction your solar panels are facing

This is another variable in solar output that is closely related to the general location of your home as well as any potential shading factors.

The general idea here is also fairly intuitive. If your solar panels are placed in the direction that receives the most sunlight, you provide them with the best opportunity to utilize solar energy.

Whether the best orientation for your solar panels is south or west depends on the physical space or roof and some differences in the surrounding environment, as well as how your utility company structures its electricity rates.

 

How to Measure Solar Panel Output

What are standard test conditions?

A good starting point is to understand the parameters for getting your solar panel's power rating. How many watts your solar panels are capable of producing could be somewhere between 250 and 370 watts.

Does this mean that your system will always generate the exact amount? Not really. That's where these variables come in. But solar panel efficiency numbers are a measure of how many watts a solar panel can produce under ideal conditions.

These ideal conditions are simulated in the laboratory where the solar panels are tested and are called Standard Test Conditions (STC). Standard test conditions for solar panel wattage mean that your solar panel is operating at 77 degrees Fahrenheit while 1,000 watts of sunlight per square meter is hitting the panel.

Therefore, a 250 watt solar panel will produce 250 watts of electricity under these ideal conditions. This standard is a good way to ensure that all solar panels are manufactured to meet specific standards. As for how they perform in the field, let's get into some of the variables.

 

Solar Panel Efficiency

What exactly is solar panel efficiency? While wattage tells you how much electricity your solar panel will produce under ideal conditions, efficiency tells you how much sunlight your solar panel is able to convert into electricity you can use in your home.

For example, if your solar panel has an efficiency rating of 13%, this means that 13% of the sunlight that hits the solar panel will be converted into the energy you need to bake bread or wash clothes.

The efficiency of a solar panel can be affected by a number of variables themselves that can inhibit or boost it. Within the solar cell itself, the efficiency may vary depending on how reflective the cell is. Cells with lower reflectivity can collect more sunlight and use it, rather than reflecting it back into space.