In the first part of this series, pv magazine reviewed the productive lifespan of solar panels, which are quite resilient. In this part, we examine residential solar inverters in their various forms, how long they last, and how resilient they are.
The inverter, a device that converts the DC power produced by solar panels into usable AC power, can come in a few different configurations.
The two main types of inverters in residential applications are string inverters and microinverters. In some applications, string inverters are equipped with module-level power electronics (MLPE) called DC optimizers. Microinverters and DC optimizers are generally used for roofs with shading conditions or sub-optimal orientation (not south-facing).
Image: Solar Reviews
In applications where the roof has a preferable azimuth (orientation to the sun) and little no shading issues, a string inverter can be a good solution.
In a string inverter, there is generally less complicated wiring and a centralized location for easier repairs by solar technicians. Typically they are less expensive, said Solar Reviews. Inverters can typically cost 10-20% of the total solar panel installation, so choosing the right one is important.
How long do they last?
While solar panels can last 25 to 30 years or more, inverters generally have a shorter life, due to more rapidly aging components. A common source of failure in inverters is the electro-mechanical wear on the capacitor in the inverter. The electrolyte capacitors have a shorter lifetime and age faster than dry components, said Solar Harmonics.
EnergySage said that a typical centralized residential string inverter will last about 10-15 years, and thus will need to be replaced at some point during the panels’ life.
String inverters generally have standard warranties ranging from 5-10 years, many with the option to extend to 20 years. Some solar contracts include free maintenance and monitoring through the term of the contract, so it is wise to evaluate this when selecting inverters.
Image: Enphase Energy
Microinverters have a longer life, EnergySage said they can often last 25 years, nearly as long as their panel counterparts. Usually, these inverters have a 20–25-year standard warranty included. It should be noted that while microinverters have a long warranty, they are still a relatively new technology from the past ten years or so, and it remains to be seen if the equipment will fulfill its 20+ year promise.
The same goes for DC optimizers, which are typically paired with a centralized string inverter. These components are designed to last for 20-25 years and have a warranty to match that time period.
Failures
A study by kWh Analytics found that 80% of solar array failures occur at the inverter level. There are numerous causes of this.
According to Fallon Solutions, one cause is grid faults. High or low voltage due to grid fault can cause the inverter to stop working, and circuit breakers or fuses can be activated to protect the inverter from high-voltage failure.
Sometimes failure can occur at the MLPE level, where the components of power optimizers are exposed to higher temperatures on the roof. If reduced production is being experienced, it could be a fault in the MLPE.
Installation must be done properly as well. As a rule of thumb, Fallon recommended that the solar panel capacity should be up to 133% of the inverter capacity. If the panels are not properly matched to a right-size inverter, they will not perform efficiently.
Maintenance
To keep an inverter running more efficiently for a longer period, residential installer Those Solar Guys recommended choosing a cool, dry place with lots of circulating fresh air. It also suggested avoiding installing in areas with direct sunlight, though specific brands of outdoor inverters are designed to withstand more sunlight than others. And, in multi-inverter installations, it is important to be sure there is proper clearance between each inverter, so that there isn’t heat transfer between inverters.
Image: Wikimedia Commons
Those Solar Guys said it is best practice to inspect the outside of the inverter (if it is accessible) quarterly, making sure there are no physical signs of damage, and all vents and cooling fins are free from dirt and dust.
It is also recommended to schedule an inspection through a licensed solar installer every five years. Inspections typically cost $200-$300, though some solar contracts have free maintenance and monitoring for 20-25 years. During the checkup, the inspector should check inside the inverter for signs of corrosion, damage, or pests.
In the next installment of the series, pv magazine will examine the life of residential battery energy storage applications.
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I am on my third string inverter on a single-inverter system installed in 2018. You can argue whether this is an unacceptable failure rate–but installers around here want as much money to retrofit micro-inverters as to install a complete new system.
What is not acceptable are the lengthy delays to replace a failed inverter. That delay was 2 to 4 months in my situation. Why so long?
First, I have to notice the problem. Now that my system is no longer new, I don’t check the app every day. So my first notification of a problem is a jump in my electric bill. Really? That’s the best that an internet-connected inverter can do? Both the installer and manufacturer ought to have automated daily scanning to detect non-communicating inverters, then contact the customer and verify a problem.
Second, I have to wait for the manufacturer to run remote diagnostics on my inverter. Even though this delay is only a few days, the installer ought to be able to run such diagnostics at the push of a button, just like the manufacturer does.
Third, I have to wait for the manufacturer to ship out a replacement inverter. After my first failure, the replacement was shipped out in a couple of weeks. But after the second failure, I had to wait several months. Neither installer nor manufacturer maintain inventory, and new sales are prioritized over warranty replacements.
My solution for this problem would be to purchase a spare inverter. The installer would keep the spare at his shop and be responsible for using it on jobs or other warranty claims to keep “my inverter” always fresh and under manufacturer’s warranty. This is common practice in other industries with critical equipment. As customer-owned material, the inverter won’t be subject to business inventory taxes. Both manufacturer and installer profit on the sale of the spare inverter. The installer additionally benefits by being able to take the inverter with him when diagnosing a problem–one truck roll fixes it. I benefit by minimizing downtime on a component that has a design life of 12 years and a history of premature failures.
If the inverter manufacturer and installer would take these two steps, my downtime after inverter failure would be a week or possibly two. That’s a major improvement, and it doesn’t cost either party much to achieve it.
I have the pleasure or displeasure of monitoring slightly over 2,100 solar installs. I have the data. From your description, I likely know which inverter you have and see this brand of inverter fail almost daily. I have seen them fail right out of the box. In 2019, there was a resistor issue causing failures and now it’s a problem with the capacitor. Absolute junk! Not a statistical aberration but a manufacturing defect.
What make and model of that Inverter and was it actually installed as per manufacturers’ specifications? Repeated, premature failure is a statistical outlier and something is wrong.
Rather than purchase a spare inverter of the same type, purchase a more popular brand (with a good track record). Remote maintenance and/or alarm monitoring is a value added feature you may have to pay for. However, there should be a way to relay a maintenance alarm to either a panel inside the the home or even an app on your phone or computer.
The failed inverters were SolarEdge series HD Wave. The first failed inverter was rated at 7600 VA and the second at 10000 (I paid extra to upsize it). My peak production is around 8500 Watt. The installer has been in business since 2011, and their installation crew was experienced. I have every reason to believe it was installed per manufacturer’s instructions.
Had I been offered a choice, I would have chosen micro-inverters at the outset because I understand how they work. I do not understand how power optimizers work, but that was what the installer was pushing at the time.
The solar power industry doesn’t publicize failure rates, so it is difficult for the consumer to simply “purchase a more popular brand (with a good track record).” Solar Edge has been in business for 16 years and sells $2 billion a year. And I’m not convinced that a BrandX inverter would work with my existing power optimizers and wiring.
“Remote maintenance and/or alarm monitoring is a value added feature you may have to pay for.” Sign me up for that Paul McGown. Sadly, however, that’s not a service the industry is offering, hence my comments about it being a market opportunity in my initial post.
I also stand by my desire to pay for a spare inverter, to be kept by my installer with inventory rotated so I receive one that was recently manufactured when the time comes. I agree that my installation appears to be a statistical outliner given its failure history, but it’s up to the inverter manufacturer and installer to figure out whether there is a product application issue, installation defect or ridiculously high product failure rate that are causing my unreliable service.
Me and my wife just purchased a home in Hawaii with an existing solar system on it. The system is less than two years old and it was a leased system that we had to sign the solar lease in order to purchase the home. One month after moving in the solar quit working and we were told it was a bad inverter. Sunnova is the company servicing the lease and the system. We have been without solar for about six months now and I call or email Sunnova at least once a week for updates and they keep giving me the same canned answer that parts are on order with no idea of when they will have my system running again, and to add insult to injury we are still required to continue making lease payments in addition to paying for power off the local grid. I have never had solar on a property until we moved here, so far I have not been impressed with the cost verses benefit. I have read alot about how customers are taken advantage of after contracts are signed with solar companies and services after the sale are lacking. Not sure who to contact when you run into a wall with companies like Sunnova that continue to charge for a service that you are not receiving, and can not provide you with creditable information on when you can expect service again. Is there a some entity out there that holds these companies responsible?
Hello Brian,
A lease is a contract. Are you sure, Sunnova is fulfilling their side of the contract? If not, then you should seek being at least temporarily relieved from your side of the contract too. Though you would need legal advise to not be the offending party yourself.
It is most likely that there is a minimum production guarantee clause in the lease to cover your loss. If the system does not produce at least as much as the guaranteed production, you will receive a payment at annual true-up.
First, when putting pictures of techs doing maintenance, maybe use a picture of them wearing proper PPE. Doubt seriously that collared shit is CAL rated.
Second, most string inverters do have a push button system on the display front of the inverter. You can Google Manuel’s for your make and model to find the fault codes.
Third, if you’re having a problem with your solar company doing repairs, find the maker of the inverter/panels, the warranties on them are them are through the manufacturer, not the solar company. The solar company warranties their work and is under contract to perform work. Most monitoring and/or micro-inverters will back date any loss of power. If not, like a full string inverter causing loss of production, read your contract, most companies are responsible for loss of production.
We’ve had plenty of trouble with a three phase 480V inverter combined with individual panel dc control modules. Several panel models have failed. The inverter has failed. We’ve lost 15% or more of production in 6 years of operation. The installer went out of business and we’ve been unable to find a dependable local source of maintenance. The inverter manufacturer’s help desk has been the most useful but they limit what they will do for us in the absence of a local rep they consider credible yet can not supply us with recommendations. The situation has catch 22s on its catch 22s. Maintenance of distributed solar panel installations is going to have to improve a lot if they are to play a role in reliable energy production.
For home use: What brand you buy and who you buy it from really matters. Ensure the local installer stands behind it and covers warrantee labor for a good 10 years if possible. There are many bad companies out there selling solar who don’t stand behind it and don’t care about the customer once they have money in hand.
Avoid leases, too many issues and you are still on the hook regardless. If you can’t afford it, get a loan, not a lease. If it won’t pay off and break even in at least 8 to 12 years then get another quote or don’t do it.
Microinverters with 25 year warrantee are best in my opinion. If one fails, the rest continue working and producing power, so you are only loosing a small percentage of production (instead of loosing all production) while you wait for the warrantee replacement.
I had panels installed in 2012. They used Enphase microinverters. The original ones were version 1 inverters. They started going out around 5 years. They were under warranty so they were replaced quickly. Soon after that Enphase offered me a deal where I could purchase their newest inverters, version 7 for their cost or below. They said the new microinverters had a significantly longer life and longer warranty as well as more efficient!
I continue to cringe when folks tell me they have a string inverter. I helped a neighbor replace their string inverter with microinverters not long ago. They are working great!
Enphase microinverters come with lifetime online monitoring as part of the deal. It usually takes less than a week for Enphase to notify me of a possible issue! I do have shading issues due to a neighbor’s oak tree so that makes the microinverters that much more efficient as well.
Business purpose
What can we do to get a refund on the cost of electricity we pay when the inverters not working
Have you been successful in this? I Just found out my inverter has been out since 9/12/22 (8 months). I have definitely lost a lot of money on energy paid while not producing anything for 8 months due to a failed inverter.