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What Is a Microinverter? A Guide for Homeowners

String inverters have long been the standard in residential solar systems. However, microinverters – a technology that came a bit later – are quickly gaining popularity as more homeowners realize their significant benefits.  The question is, should you jump on the microinverter bandwagon or would you be better off sticking with the traditional inverter setup? In this article, I’ll take you deeper into what a microinverter is, how it works, and its pros and cons to help you make sense of it all and decide whether it’s the right choice for your home.

What Is a Microinverter and How Does It Work?

A microinverter is a small device attached to each solar panel in a photovoltaic (PV) system. It converts the direct current (DC) electricity generated by the panels into alternating current (AC) electricity that your home can use.

Doesn’t a string inverter function the same way? Of course. However, unlike traditional string inverters, which handle this conversion for all panels collectively, microinverters work on a panel-by-panel basis…

This means that every panel converts its DC output to AC independently, directly addressing the primary limitation of traditional string inverters: if the central inverter fails, the entire solar panel system stops working.

In contrast, with microinverters, the rest of your system keeps operating even if one unit breaks down.

With that said, microinverters certainly come with several advantages, but like anything else, they also have their downsides.

Advantages of Microinverters

Localized Failure

Inverters tend to experience the most stress in a solar system and, therefore, are the components most likely to face performance issues or malfunctions.

In the case of microinverters, if one unit malfunctions or fails, the rest of your solar system continues to operate. You can still power your home with the energy harnessed by other panels, free of energy interruption.

On the other hand, if a central string inverter fails, the entire system goes offline until it’s repaired or replaced.

So, the real benefit of microinverters then is that they buy you time – time to address and repair any faulty units without losing power, and without experiencing the downtime that comes with waiting for service.

Flexibility for System Expansion

The thing with string inverters is that they’re designed to handle a set number of panels, and their capacity is usually determined when your system is first installed…

This means if you start with a smaller solar system today (perhaps due to budget constraints or limited space) you might not be able to expand your system that easily. 

With microinverters, you have a “decentralized” system that allows you to add panels in the future without thinking about overloading. As each panel gets its own microinverter, there’s no need for major upgrades, replacements, or rewiring of any existing equipment.

Flexibility for Panel Placement

Not all parts of your roof get the same amount of sunlight. Some sections receive less sunlight due to their direction, while others have steep angles or obstructions that cast partial shade, thereby reducing panel efficiency.

This becomes an issue with central string inverter setups since the weakest-performing panel drags down the efficiency of the entire string.

Microinverters, on the other hand, eliminate this problem by decoupling the panels. So, if one panel is shaded, only that panel’s output is affected – every other panel continues to produce energy at full capacity.

This means you don’t have to stress about forcing every panel into ideal conditions (although that’s always preferable). Microinverters ensure that each panel operates independently and always performs at its highest possible efficiency.

Compliance With Module-Level Rapid Shutdown Requirements

Module-level rapid shutdown (RSD) is a safety feature designed to de-energize individual solar panels quickly in the event of an emergency, such as a fire

Essentially, it ensures responders, maintenance workers, or anyone accessing the roof can do so safely without the risk of high-voltage electricity from the panels. For this reason, RSD has become mandatory in many U.S. states, including California, Texas, and Michigan.

Microinverters inherently meet module-level RSD requirements because they operate at the panel level – unlike string inverters which require add-on components for compliance.

Panel-Level Monitoring Capability

Microinverters let you monitor the performance of each individual panel, making it easy to identify which panels are malfunctioning or underperforming.

This level of detail simply isn’t possible with string inverters, which only provide system-wide or string-level data.

That said, if you’re someone who’s particular about individual panel performance – or deeply committed to going for the most optimal route possible (just like I am) – go with microinverters instead of string inverters.

Longer Lifespan

Let me preface this by saying that lifespan definitely depends on factors like component quality and environmental conditions. That’s why many homeowners report inverters breaking down as early as two years.

But for the purpose of comparing lifespans, let’s look at warranties instead.

Microinverters come with warranties of 20 to 25 years, while string inverters usually have warranties of 8 to 12 years. This means that with microinverters, you can expect to avoid the hassle of replacements for a long time.

Disadvantages of Microinverters

Higher Upfront Costs

Microinverters are built with a different technology and design compared to string inverters – and that alone drives up the price. 

Besides that, in a more practical sense, there also comes a point where using microinverters might actually exceed the cost of applying the traditional string inverter system.

Let’s crunch some numbers with a hypothetical scenario where you’re installing a 4 kW solar system – 12 solar panels, for example. Assuming the cost of each microinverter is around $300, for 12 panels, you’re looking at a total of $3,600 for microinverters.

Compare that with the cost of single string inverter capable of handling all panels of the 4 kW system, around $2,000, and you would save about $1,600 by choosing the string inverter setup.

Although, I want to make it clear that this is a very simplified example. 

In reality, there are many factors to consider when comparing the two cost-wise, such as the complexity of installation, RSD requirements, personal preference, and so on – all of which are things I and the Avail Solar team takes into account before settling on either option. 

Potential Challenges With Maintenance

As I mentioned, microinverters come with warranties reaching up to 25 years, which says a lot about their lifespan, reliability, and low-maintenance features.

But here’s the thing. A microinverter can still fail, perhaps due to issues like suboptimal connections or manufacturing defects (this can happen even with reputable brands).

And since each panel has its own microinverter, it’s hypothetically possible for failures to occur at different times – one might fail today, another in a few months, and so on…

In this case, the cost isn’t the issue as the warranty will take care of it. The real concern is the inconvenience of having to call for service multiple times.

(Again, this doesn’t happen often, but it can absolutely happen.)

In contrast, with a string inverter setup, only one unit is needed for the entire array, which means you typically only need to call for maintenance once – usually, only if there’s a major issue with the inverter itself.  

Efficiency Losses in Battery Storage

Remember that microinverters work by converting the DC into AC electricity at the panel level. This means electricity generated by your solar system is already in AC form.

But, since most solar batteries are designed to store DC power, you would need an AC-coupled battery inverter to convert the AC back into DC for storage.

This means energy goes through three conversion stages, resulting in more energy loss compared to just two conversion stages in a traditional string inverter setup. 

When to Choose Microinverters

Personally, I’d recommend you choose microinverters only if:

  • Your roof/property gets a lot of shading, whether from trees, nearby buildings, or other obstructions; and
  • You’re planning to install a relatively small system say, 3 kW to 5 kW

Outside of these scenarios, you may want to consider a traditional string inverter setup with optimizers, which works just as well as microinverters in terms of improving shade tolerance and tracking individual panel performance.

Generally speaking, the costs between the two inverter technologies can be pretty similar. However, the nuances – such as your specific shading conditions, system size, and future expansion plans – will greatly influence which choice is better for your home. 

Need a Certified Solar Panel Installer to Help You Decide?

Making the right decision doesn’t have to be overwhelming when you have a solar expert guiding you throughout the solar transition process.

Before installing either microinverters or string inverters, we at Avail Solar first look at your energy consumption needs, long-term goals, and the specific conditions of your home. Once we have all that information, we make a decision that best fits your situation – eliminating all the guesswork from the process.

Request a quote today or give us a call to speak with one of our solar experts!

Posted in Solar 101