Measuring Solar Panel Efficiency

In a climate of rising fear over dwindling fossil fuels, homes and businesses have begun installing solar panels to augment or replace their current energy systems. These panels are relatively simple to maintain, but dirt and improper placement can significantly decrease their power output. In order to ensure that you are obtaining the optimal value from this product, you should regularly check the efficiency of your solar panels. This is a simple procedure, requiring little more than multimeter, and it will maximize your savings.

First, you need to determine the area of your panels. If you don't have that data from the installation, just use a measuring tape.

Second, you need to figure out the maximum solar radiation for the exact spot on Earth where your solar panels are sitting. Essentially, this is a measurement of how much power the sun is bringing to your location — i.e., the maximum power your solar panels could theoretically provide, keeping in mind that current panels achieve only a maximum of about 20% efficiency. You can measure solar radiation with a solar meter, or you can look at the database on the National Renewable Energy Laboratory's website, which provides average solar input for various regions throughout the year. 

Now you need to figure out how much power your panel is actually providing. Use a multimeter to measure the voltage and current that your panel is producing, then multiply these figures to calculate the power produced (P = VA). Keep an eye on your units — your panel area should be in meters squared, and your power should be in kilowatts.

To determine your panel's efficiency, just divide the power output of your solar panel by the solar input of your location (both in kilowatts per meter squared) and multiply by 100. If the number is lower than it should be (around 20), you may need to clean your panel, adjust its angle or ask a professional to inspect it.