How to Measure Solar Panel Output

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Ever wondered how to measure solar panel output? So, it’s been a little while since you installed your solar panels and you’re beginning to notice that something just isn’t quite right.

Although the solar panels generate a lot of power it seems that your batteries don’t seem to be charging as well as they should and you’re beginning to think that there might be a problem with your solar panels or their installation or they’re just simply not providing enough power for your needs. 

Now of course you already know that they’re multiple variables that can affect the performance of solar panels (e.g., weather, time of day, location) but you want to get an idea on how they’re performing relative to what you’ve expected or at least hoped for.

First of all if there are problems with either the installation or with the actual performance of your solar panels then it’s probably best that you find out about them when it doesn’t matter so much rather than later when hopefully it will be too late. 

So how do you know if there really is a problem? A good way to tell if your solar panel installation is performing as expected is by measuring the current and voltage output from each of your individual solar panels over time. A digital multimeter will help you accomplish this task quickly and easily for minimal expense. Below we provide details how you can use this tool and information to determine if your solar panel installation is performing as expected.

Why Should You Test Your Solar Panels?

Why Should You Test Your Solar Panels?

Before we get into that though let’s first understand why exactly it is important to measure the output power of your solar panels and not just assume that they’re providing you with all the power you need. If your solar panels are underperforming, you’ll be missing out on all their benefits including a huge reduction in electricity costs, pollution and a source of clean renewable energy. 

The expected power output rating that you see when you first purchase your solar panels describe the ideal environment in which they’re tested. Manufacturers do this by simulating a set of solar panels mounted in a perfect position, with light hitting the panels perfectly head on and at the correct angle.

However, conditions in the real world are typically different than what is found inside a laboratory so it’s possible that your solar panels might not be performing as expected which you want to know about before more time passes.

As these conditions are ideal conditions created in a lab, they’re not exactly real world and your solar panel installation is unlikely to ever produce the exact same results as those provided by the manufacturer

In order to make sure that your solar panel system provides you with enough power you should be testing them in real world conditions and verifying their performance relative to what is expected given their location.

Solar panels should be tested to ensure that they are generating the amount of solar energy that you expect. Adjusting your expectations to more accurately reflect the real capability of your solar panels would not only allow you to do this, but it will also let you know whether you need to buy more solar panels or just re-orient the ones you currently have.

Essentially, testing your solar panels will allow you to ensure that they are producing enough power and, if necessary, tell you whether or not they need to be reinstalled in order for you to optimize their performance and get the most out of your system.

How to Measure Solar Panel Output

How to Measure Solar Panel Output

Now that you’ve decided that it’s important to test your solar panel installation you need to determine how exactly you’re going to accomplish this task. There are several different methods you can use depending on how much time, effort and money you want to spend in order to get the job done but we’ll focus specifically on using a multimeter and amp meter in this article. 

After you are done purchasing a both devices or have taken out the ones you already own, it’s time to find out how this is done which would provide straightforward, accurate results relatively quickly. 

First, you’ll want to place your solar panels in an area that receives direct sunlight without obstruction because the energy output of your solar panels is dependent on the amount of light hitting them. Make sure that it’s a super sunny day and that there are no shadows that might be cast on the solar panels by trees, other buildings or even other panels. The best time of day to this is to do it between 10 AM and 3 PM when the sun is highest and brightest in the sky during the middle of the day.

1. Start by Noting the Power Rating:

Start by Noting the Power Rating

The first step in learning how to measure solar panel output is to simply take a look at the power rating of your solar panels and write it down. This can usually be found on a sticker that is placed on the panel itself or in the owner’s manual. 

2. Then Measure the Solar Panel Amperage:

Measure the Solar Panel Amperage

The second step is to measure the solar panel’s amperage which can be done with an amp meter. To do this, you’ll need to find a spot where you can safely touch the two probes of the amp meter to the two wires that are coming from the solar panel. It’s important to note that you should not measure the amperage when the panel is connected to an inverter or any other device as this will give you an inaccurate reading. 

3. Next Measure the Solar Panel Current:

Measure the Solar Panel Current

The third step is to measure the solar panel’s current which can be done with a multimeter. This is done by placing the black probe of the multimeter on the negative (-) terminal of the solar panel and then placing the red probe on the positive (+) terminal. 

4. Calculating the Power your Solar Panels are Producing

Calculating the Power your Solar Panels are Producing

Now that you have these measurements it’s time to do a little math in order to find out the wattage that your solar panel is producing. Now you will need to calculate to get the power output for your solar panel. Simply use the previous voltages and amperages, plus the following equation: watts = volts x amps.

Once you’ve figured out the total wattage of your solar panels, you may multiply this figure by the average number of hours of sunshine you receive each day:

Solar panel watts x average hours of sunlight = daily watt-hours

Normally, you take 75% of this total, since direct sunshine will not be same all day. Unless you want to check your solar panels multiple times a day, performing the test during a peak sun hour and then multiplying your daily watt-hours by 75% should be a good approximation of their performance.


Testing your solar panel installation is an important step in making sure that you’re getting the most out of your investment. By using a multimeter and amp meter, you can measure the voltage, amperage and current of your panels and then calculate their power output. Make sure to do this test on a sunny day and take into account the average number of hours of sunlight you receive each day. This will lead to an accurate estimation of the power your solar panels are producing.

If this article about taught you how to measure solar panel output, consider checking out these other article:

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