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How can I tell if my solar panels are working properly?

Avatar for Ben Zientara
Published on 04/07/2015 in
Updated 10/18/2016

Shade is the output killer (sometimes).

So you’ve got a shiny new solar installation on your roof, and it’s just started kicking out the kilowatts. How do you know that every panel is producing up to its potential? What if one or more of your solar panels breaks? Will the others keep working?

These are all excellent questions, and, fortunately, they’re also pretty easy to answer. But first let’s get into the particulars of how solar panel systems are set up:

With One Inverter

For a traditional solar panel system, panels are placed on the roof, and rows of panels are wired in strings. The strings are connected at one end of the system and the wires are run to a central inverter, which takes the DC electricity from the panels and changes it to AC electricity that can be used by your home appliances and the rest of the electrical grid.

In this kind of system, if a single panel isn’t working, the whole string goes down, kind of like if you cover half the panel on a solar calculator with your finger, the calculator won’t work.

Fading… fading… fading… don’t let this happen to your panels.

This loss of power can also be experienced if a couple of your panels are extra dirty or shaded. You’ll know if a panel in your system has problems because the system output in kilowatt hours (kWh) will be lower than it should be. Many companies that install solar panels offer some kind of system monitoring software that can help.

If you suspect a problem and your system is within its installation warranty period (typically 10 years), call your installer to have them come check each panel. If your system is outside the installation warranty period but within the manufacturer’s panel warranty (typically 25 years), you may have to do a little bit of work to coordinate the repairs.

If your panels have been up for a while, you might be able to tell easily by looking at your electric bill whether your system is producing, but if you’ve just had panels installed, you’ll have to go by estimates provided by your installer (or you can take a look at our handy calculator to see how much energy your panels should be producing). Remember that even a little shading on a couple panels in a string can cause a big dip in production for that string.

With Micro-Inverters

Many modern solar panel systems are installed with micro-inverters attached to each panel. While these micro-inverters can be more expensive than a single, centrally-located inverter, they also separate each panel’s production, meaning when one goes down, the others keep working great. For systems that use micro-inverters, there is even more advanced monitoring software that can detect when one panel goes out.

Just your friendly neighborhood micro-inverter, hanging out under a solar panel.

That means your panels’ output shouldn’t decrease for any reason less than a lightning strike or other act of whatever-deity-you’re-into. That’s great news! So when you’re talking to an installer about getting a system, examine the micro-inverter option carefully. It might cost you a bit more up front, but it pays for itself in piece of mind and risk avoidance. Some micro-inverters are even warrantied for 25 years just like the panels, so they’re more durable, too.

Either way, make sure you’re getting the option for monitoring software, so you can know your typical production and be ready to take action if your system isn’t working like it’s supposed to.

Last modified: October 18, 2016

12 thoughts on “How can I tell if my solar panels are working properly?

  1. Avatar for Hamesha Hamesha says:

    I dont see a response to those who commented they are getting much less power than the amount their solar system was rated for.

    1. Avatar for Ben Zientara Ben Zientara says:

      The best thing anyone can do is look at how many kWh per day their system was projected to generate, then put the numbers for their system into NREL’s PVWatts tool, and compare the two numbers. PVWatts gives estimated production by month for a given latitude/longitude, roof pitch, etc.

      If you put your numbers into that tool and your production doesn’t jibe with what the installer promised, you can approach them with the numbers. If you got a production guarantee (common with a PPA, less so if you own the system) or a workmanship warranty, you may have some recourse and the installer should be willing to come out and run some tests on the system.

      No matter what, the panels themselves should have come with a production warranty, and the manufacturer should take care of testing to ensure the panels are working properly.

  2. Avatar for Dan Dan says:

    I live in Arizona and have had solar for three years. I purchased a 7.5 kW system. On the longest day of of the year the system was only putting out 5.5kW. The installer added 2 panels to boost the output but still can’t produce over 6.0 kW on a cloudless day. What should I expect the output to be for a 7.5kW system?

  3. Avatar for Russ Russ says:

    Same as another person, our bills are the exact same now. Albeit it is winter but even the power company was scratching their head when we called. In the summer we weee hardly making any power either. Is it possible some weee. Or hooked up right or something? How can I check if they are all working?

  4. Avatar for Anonymous Anonymous says:

    The Solar Edge users Individual power optimisers and parallel wiring to the Solar Edge inverter; each panels performance is monitored. Having changed from a serial wired system I have compared 6 previous years with the 14 months since installation using two statistical models comparing to U.K. Met Office weather. Show 3% improvement at median but salesman promised 15% to 36%.

  5. Avatar for Sirimewan Ganepola Sirimewan Ganepola says:

    The first year after installing my panels were producing close to the quoted capacity on sunny days. In May I had 28 units the highest ever. Two years later I never get even two KWH half the quoted capacity.

  6. Avatar for Pat Pat says:

    I’m looking for help in installing a solar system on my home in Florida. I need an electrician and some one to draw upthe plans. I will do the install and puchase of the panels.

  7. Avatar for Dana Watson Dana Watson says:

    We just got solar panels installed. As of 2nd billing cycle we are still paying a full electric bill. Called installer bit they have been no help with fixing problem. What is our recourse?

  8. Avatar for Anonymous Anonymous says:

    Is asking your installer, the only way to see if your panels are working? All I need to know is how I can check it myself, from home.

  9. Avatar for Anonymous Anonymous says:

    Ok.thanks. ask you for JV!

  10. Avatar for Anonymous Anonymous says:

    Thank you for this informative article. I work at a solar company in Houston, Texas and I think we’d like to point that the cost for going with a 5 kW system is not as high as your estimate. Would you mind talking to me for a reassessment?

    1. Avatar for Ben Zientara Ben Zientara says:

      Absolutely! We’ll shoot you an email.

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