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Guide To Micro Inverter Technology

Jun 24, 2022

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Inverters are a vital component of a solar panel system. Until about 15 years ago, home solar systems had one central inverter. However, since micro inverters were introduced to the market, they have been growing in popularity. Today, solar shoppers have a few types of inverters to choose from when going solar.

If you’re going solar, you can pick between having micro inverters on each solar panel or a central inverter. Of course, there are pros and cons to both. Let’s explore the topic so you can make the optimal decision based on your property and project goals.

What Is A Solar Inverter?

When light hits the solar panels, it generates an electrical current. However, the current is direct current (DC) power, which means the electrical current moves in a single direction. But, most home appliances, electronics and lighting systems use alternating current (AC) power, which means the electrons move forward and backward. AC power is more effective at transmitting electricity over long distances, and high-voltage power lines use AC electricity.

So, solar inverters convert DC power from the solar panels to AC. This enables household loads to use the electricity from the solar panels and is a critical component of a solar panel system.

Understanding The Types Of Solar Inverters

There are two main types of solar inverters: central (or string) inverters and micro inverters. In addition, there are other types of inverters for more specialized applications, but they are rare in residential, grid-tied applications.

Central Inverter

If a residential solar system has a string inverter, it usually has just one or two units. Thus, the inverter is connected to multiple solar panels to convert the electricity. In the early days of solar, this was the only option, so this inverter technology has been on the market and widely used for much longer. Common string inverter brands include SMA, Fronius, SolarEdge and Huawei, but there are many on the market.

Central inverters are typically mounted in basements or near the electrical panel. If the solar panels don’t have power optimizers, then the solar system shading can have a more significant impact on performance.

Shading on one panel can disproportionately impact the electricity output of the entire array. Likewise, the solar monitoring system doesn’t have panel-specific data without power optimizers on each solar panel. Optimizers can help overcome some of the disadvantages of a central inverter.

Micro Inverter

Unlike a string inverter, micro inverter systems are installed on the back of the solar panels themselves, and each panel has one. This allows every module to operate independently, which is important if there is shading. This is achieved through maximum power point tracking (MPPT), which optimizes the performance of each solar panel instead of the whole system.

Enphase is a very well-known micro inverter manufacturer, but there are now many other products on the market as well. Micro inverters are also used in plug-in solar panel kits.

String Inverters Vs. Micro Inverters

Let’s see how the two primary home inverter technologies compare in various areas.

Ease Of Wiring

String inverters require less complicated wiring work than micro inverters. Therefore, they are faster and easier for solar technicians to install. Often, solar contractors will have a slightly higher labor charge for projects that involve micro inverters.

Efficiency In Partial Shade

If there is shading on the roof, micro inverters can boost the production of the whole solar system because shade on one panel won’t comprise the output of others. This can make a big difference for homes with a partially shaded roof.

However, one way to overcome this issue is by adding power optimizers. Like micro inverters, they also have MPPT to mitigate the impacts of shading on one panel disproportionately impacting the electricity production of the whole system. In other words, power optimizers help monitor your panels’ output to optimize production and efficiency. Similar to micro inverters, power optimizers are also mounted on each solar panel.

Lifespan

Often, micro inverters have a 25-year warranty, which is about the same as the design life of the solar panels. By contrast, many string inverters have warranties of 8 to 12 years. Typically, warranties correspond with equipment lifespan, and it is common for solar panels and other components to outlive the string inverters.

Having a longer lifespan reduces the need to replace the inverter down the road. Also, inverters are fairly expensive, boosting the maintenance costs of your solar panel system.

Maintenance 

Many solar technicians will agree that it is easier to troubleshoot issues if a solar system has micro inverters because the monitoring system provides panel-level data instead of system-level data.

However, the actual repair might be more difficult with micro inverters. They are located on the roof, and it requires climbing up there and removing panels to track down the problem if one fails. By contrast, the string inverter is commonly located in the basement or somewhere that is much easier to access.

Price

String inverters (without power optimizers) are commonly less expensive than micro inverters. In addition, the labor expense is likely a bit less too. If you want to keep the cost of your solar power system down, having a string inverter might be a good choice, especially if partial shading isn’t an issue.

Rapid Shutdown

The National Electrical Code has rapid shutdown requirements for solar power systems. This is designed to protect electrical workers and first responders from voltage during outages or emergencies. Micro inverters satisfy this requirement, but string inverters without power optimizers may not.

System Expansion

Sometimes, solar system owners want to add more solar panels to their roofs down the line. This is especially common if a home gets an electric vehicle or switches from gas to electric appliances. Typically, it is easier to add more panels if you have micro inverters.

This is because a central inverter has a limit on its capacity. Once it reaches that limit, it starts to clip power. That means that you will not be able to use all the power produced during times of optimum production.

Therefore, homeowners often need to upgrade to a larger central inverter if they add solar panels. Unfortunately, this isn’t very cost-effective. By contrast, you can easily add more solar panels with micro inverters, but each panel will need one.

System Monitoring

Micro inverters allow panel-level monitoring. That means that you can look at your mobile app or online portal to see how much each module is producing. This is helpful if one or two aren’t working properly, and it assists with pinpointing production issues. In fact, micro inverters have unique serial numbers that are displayed in the monitoring data.

However, power optimizers with string inverters also allow for panel-level monitoring. In arrays with just a central inverter and no optimizers, you will only be able to track what the entire system is doing.

Single Point of Failure

If a central inverter fails, the entire solar power system will stop producing energy. This is an especially critical issue if the failure goes unnoticed somehow.

However, if a system has micro inverters and one fails, only one solar panel will stop producing instead of the whole array. Therefore, this failure will have a much smaller impact on the total solar electricity production.

The Bottom Line: Consider String Inverters For Price, Micro Inverters For Flexibility

Clearly, there are advantages and disadvantages to both solar inverter technologies. Often, it’s important to take the specific property and project goals into account to figure out which technology is best.

Now that you’ve learned about some of the key points of solar panel arrays and inverters, are you ready to see what’s right for your home? Consult a Rocket SolarSM Advisor today!

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