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How to Test a Solar Panel Output? – Detailed Guide for Every Step

how to test a solar panel output

Are you not curious how much power your solar panel system generates? Did you know you can easily calculate your home’s energy production if you know how to test a solar panel output? Measuring the solar panel output can help you gauge your system’s energy production capability.

Testing a solar panel output is crucial to determine its actual power generation. We know that a 300-watt panel rarely delivers that much electricity because of factors beyond our control. Measuring its power output helps us adjust our expectations, helping us decide what to do next.

Things You Need for This Tutorial


Testing a solar panel’s energy output does not require complicated steps or expensive tools. However, I do recommend preparing the following before embarking on this project.


A multitester is the single most crucial tool you need for this activity. This small device measures various electrical parameters, including resistance (ohms), current (amps), voltage (volts), and more.

Although you might want to get a dedicated solar panel output tester, a good-quality digital multitester is more than adequate.

Why do these two parameters (amps and volts) matter? Well, the solar panel’s power output is always in watts, which is volts multiplied by amps. That is why you need a device that measures the solar panel’s current (amps) and voltage (volts).

Solar Panel User Guide 

The owners’ manual contains information relevant to your solar panel’s technical specifications, performance, and maintenance. The user guide contains the solar panel’s voltage, wattage, amperage, and other electrical characteristics.

I know you are confused. If the document already has the solar panel’s wattage or power output, why do I still need to test it?

It is essential to understand that manufacturers rate their solar panels (watts, amps, and volts) based on highly controlled laboratory variables. Companies subject their solar panels to 77-degree Fahrenheit panel surface temperature and 1,000-watt sunlight exposure per square meter.

Laboratory technicians monitor these test parameters to allow the company to rate its solar panels. But, unfortunately, we do not live in a controlled environment, do we?

That is why it would be incorrect to assume that the 100-watt solar panel you have on your roof produces 100 watts of electricity all day long, every day.

Why Read the Manual?

The user guide should give you baseline information. For example, if it states the solar panel produces 200 watts, your test should validate the value. The same is true with the amps. If the solar panel user manual states that the panel runs on 3 amps, your test should confirm this.

Another reason why I recommend reading the manual is to determine the location of the solar panel’s electrical components.

Testing the solar panel’s power output requires connecting meter probes or leads to the solar panel’s positive and negative terminals. Knowing this beforehand makes the activity more straightforward.

Steps to Testing Solar Panel Output


Step 1. Check the solar panel’s electrical connections.

Your solar panel has two sides – one shiny that absorbs light energy and another that forms the panel’s platform. Check your solar panel’s underside and look at the wires connecting to a small box in one of the corners or sides.

The small box is the solar panel’s converter or junction box, transforming light energy into electricity for storage in deep cycle batteries or straight to an inverter. Check the positive and negative terminals in the converter.

Pro Tip: You can also check the solar panel’s user manual for these components’ locations.

Step 2. Ensure your solar panel receives the same amount of sunlight it normally gets.

Solar panel testing requires you to take the measurements in the same operating conditions the system undergoes every day. You will want the solar panel at its optimum position and angle to receive maximum light energy.

It would also be best to check the sky, delaying the testing if it is cloudy. You can still measure the solar system’s power output, but the results will be less than what you expect.

Step 3. Measure the solar panel’s amperage using a multimeter.

  • Power on your multimeter and set the dial to “amps.” You can also use an ammeter if you do not have a multimeter.
  • Touch the meter’s red probe on the solar panel’s positive terminal before doing the same with the black electrode on the negative wire.

(Here is an informative video from GM Genuine Parts & ACDelco on checking a device’s amperage with a multimeter)

  • Check the reading in the multimeter. It is normal to see 3.0 amps in normal conditions, although the reading can be as high as 6.0 amps on unusually bright days.

You might have a problem with your solar panel if the amperage rating is lower than 2.0. I suggest checking all connections and the panel’s photovoltaic surface for cracks or signs of damage. A loss in structural integrity can reduce a solar panel’s energy-generating capability.

Note the amperage reading because you will need it to check solar panel output. Write it down if you must.

Step 4. Determine the solar panel’s voltage.

The next step to determining how much power your solar panel generates is to check its voltage. This step is almost similar to measuring the system’s amperage using a multimeter.

  • Plug the black lead into the multimeter’s COM port and the red electrode into the jack marked “V/Ω/Hz.” Set the meter to DC and rotate the dial to a voltage level slightly higher than the solar power’s voltage rating.
  • Touch the red electrode’s tip on the solar panel’s positive terminal and the black lead on the negative connection. Check the result in the meter’s display. Note the reading because you will need this for the next step.

I found Ratchets And Wrenches’ video on using multimeters to read voltage beneficial for this step.

Step 5. Calculate your solar panel’s power output.

You are now ready to determine your solar panel’s energy production capability. You only need to multiply the amperage by the voltage readings to obtain the solar panel’s power output in watts (Watts = Amps x Volts).

Suppose your solar panel testing showed 3.0 amperes and 12 volts. In that case, your solar panel generates 36 watts (12 volts x 3 amps = 36 watts).

Step 6. Calculate the solar panel’s daily power output.

It would be wise to understand that the value we calculated in Step 5 reflects ongoing solar power generation only. It does not reflect the solar panel’s daily power output.

You can multiply 36 watts by the number of peak sunlight hours in your location. Let us say you enjoy five hours of direct sunlight all day long. In that case, your solar panel produces 180 watt-hours every day (36 amps x 5 hours = 180 watt-hours).

Unfortunately, the calculation does not end there. You also need to multiply the result by 75% to account for factors impacting solar power generation. Hence, the 180 watt-hours become 135 watt-hours.


Now you know how to test a solar panel output. You can perform this procedure every day and record the results. You can take the daily average after a month of observation to get a more accurate understanding of your solar system’s power generation performance.

I hope you found this guide advantageous in determining your solar system’s power output. If you think so, other people will appreciate it if you share this tutorial with them. Upon queries or feedback about this tutorial, hit me up, and I will get back to you as soon as possible.

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