what are string inverters

String Inverters: What You Need To Know?

String inverter converts DC (Direct Current) electricity from solar panels to AC (Alternating Current) electricity. As, bringing more solar energy into our day-to-day life as most of our appliances use AC electricity.There are 4 different types of solar inverters: standard string inverters, optimized string inverters, microinverters, and hybrid inverter systems.

Let us discuss in detail what string inverters are, the pros, cons, and factors to consider when buying string inverters. Also, you will know the procedures of installing string inverters and how you can manage replacing a string inverter given their shorter lifespan compared to solar panels. Most importantly, we will discuss how you can upgrade your string inverter system to accommodate future solar panel additions.

What are String Inverters? How String Inverters Work?

what is string inverterA string inverter is a device that connects multiple solar panels in a series or a ‘string’ formation. Also, these are the most commonly used central component in many solar installations.

Functioning of string inverters is to combine power output from multiple solar panels into strings and enable the usage of solar energy in our homes or businesses. In simple words, string inverters collect all the DC electricity from each solar panel and convert it into AC electricity, which can be used for many home appliances or business equipment.

The design and operational mechanism of string inverters allows functioning in a series like multiple strings of panels, where each solar panel is arranged in a row and their outputs are combined. Further, these strings of solar panels are connected to a single inverter, usually located inside the electronic box placed outside your house or in the garage. Hence, the string of multiple solar panels is connected to a single inverter that converts the electricity from DC to AC.

The difference between string inverters and other inverters is that it doesn’t individually handle each panel, instead, it collectively manages the power output of entire panels in a string. For example: Microinverters are directly mounted on each solar panel, thus converting electrical current from DC to AC at the source. The string inverters are mounted on your house, collecting the DC electricity from all the panels and converting it into a centralized location.

Like string inverters, central inverters are used in big projects similar to string inverters but are much more capable of handling large amounts of solar energy. Hence, they are used in community and utility-scale solar farms. There are so many differences between string inverters and central inverters you should know.

Pros of String Inverters

There are many advantages of string inverters which include cost-effectiveness, high efficiency, ease of maintenance, and scalability.

Cost-Effectiveness: One of the main reasons why string inverters are preferred and popular is due to their affordability. String inverters are comparatively very less expensive than microinverters or power optimizers. Hence, these are the best budget-friendly solutions for many solar installations without compromising on performance. Especially for the systems with many solar panels.

High Efficiency: String inverters are designed in such a way that they surpass the efficiency rate of 95%. Hence, this means these string inverters are capable of converting the maximum amount of DC power collected from solar panels into usable AC power. However, a few latest models of string inverters are capable of attaining an efficiency rate of up to 99% which is remarkable.

Ease of Maintenance: The installation, maintenance, and troubleshooting of a string inverter is far simpler compared to the microinverters or power optimizers. And, this is because they have very few components and wires. Also, there is only one central unit to manage, so it is less expensive to maintain.

Scalability: String inverters make it very easy to add more panels to the existing system or replace a malfunctioned panel. Even if you feel like expanding it in the future, string inverters give options for your solar system growth over time.

Cons of String Inverters

Despite having great advantages, the sting inverters also come with certain disadvantages. These drawbacks include limited performance monitoring, reliance on a single point of failure, challenges in expanding the system, and a shorter lifespan compared to other solar panel systems.

Limited Performance Monitoring: String inverters are not capable of panel-level monitoring, instead they provide the overall system performance data. Hence, this means that individual solar panel monitoring can be very challenging and does not give precise results like in the microinverter or power optimizers.

Single Point of Failure: If a single panel in the string gets shaded or produces less energy, it will lead to downtime or cease producing AC power in the entire string of solar panels. Thus, it makes the entire string of multiple solar panels inoperable and the other panels will start matching the outcome of the shaded panel. There are also so many reasons for solar inverter failure you should know.

Challenges in Expanding the System: Although the string inverters allow good scalability, if your power needs are increasing it could be difficult. Because, if you are willing to add more panels beyond the inverter’s capacity, it might require an additional inverter. Remember that, once the string inverters are installed you cannot alter the ratings which will restrict the expandability of your solar system in the future. And, you might need a 2nd central inverter installation, which will incur extra cost.

Shorter Lifespan: String inverters usually have a shorter lifespan than other solar panel systems, which last up to 25 years. Generally, the lifespan period ranges from 10 years to 15 years, after which it might need a replacement.

Factors to Consider When Buying String Inverters

While purchasing a string inverter, you will have to follow the following factors:

  • Price: String inverter prices vary based on brand, capacity, and features. Typically, the string inverters price in the USA ranges from $1,000 to $2,000.
  • Efficiency: You will have to look for inverters with high-efficiency ratings to achieve the best energy conversion. Because only high-quality inverters tend to convert more electricity with just a few power losses.
  • Sizing: It is important to size the inverter’s capacity depending on the solar array’s size and estimated power output. You need to make sure that the inverter size matches the solar array size and geographic location so that you can experience an excellent power conversion.
  • Durability: The most influential factor for durable performance is buying the inverter from a reputable manufacturer with a proven track record of reliability. On average, a string inverter’s lifespan ranges from 10 years to 15 years. However, if installed in a cool, well-ventilated location and maintained properly then it could easily last up to 20 years.
  • Warranty: Warranty terms are a very influential factor that ensures the long-term reliability of the string inverter. Hence, kindly make sure to check the coverage for possible defects or unexpected failures by properly checking the warranty terms.

How To Install String Inverters

The installation process of string inverters is carried out in several steps, which are ideally considered to be performed only by a qualified and reputable solar installer. This is because the experienced technician will make sure that the system is sized and installed properly.

Here is the step-by-step process involved in installing a string inverter:

  • Mounting the Inverter: The first and foremost task is to select a suitable location that is shaded, well-ventilated, and easily reachable.
  • DC Wiring Connection: Now, the positive and negative wires of each string of solar panels are connected to the inverter’s DC input terminals.
  • AC Wiring Connection: AC output from the inverter is connected to the electrical panel or a specially designated circuit breaker.
  • Grounding: The inverter and all other wiring have to be properly grounded as the best safety measures.
  • Commissioning: After the wiring works are done, it is the responsibility of a qualified electrician to commission the system and make sure it is perfectly operating.

Although it is possible to install the string inverters by yourself, we would recommend hiring a professional installer or electrician. In that way, you would have complete safety as well as compliance with local regulations.

How Do I Manage Replacing a String Inverter Given Their Shorter Lifespan Compared to Solar Panels?

In cases where your string inverter has reached or is about to reach the end of its lifespan, you should replace it immediately. And, in this way, the string inverter’s efficiency and functionality of the solar power system will keep going without hindrance.

When the string inverter has to be replaced, you need to contact a well-qualified solar installer or the manufacturer to start the replacement procedures.

Remember that if you are going to upgrade your string inverter or opt for an extended warranty, it will be very helpful to maintain the continuous operation and possibly extend the inverter’s lifespan covered under the manufacturer warranty.

Most importantly, you should take care of disposing or recycling the old string inverter properly for the sake of a healthy environment. Also, you must follow the local regulations and other manufacturer guidelines about recycling or disposing of electronic equipment.

Can I Upgrade My String Inverter System to Accommodate Future Solar Panel Additions?

Yes, it is possible to upgrade a string inverter system to accommodate future solar panel additions. However, before you think of upgrading you need to consider several factors including the existing inverter’s capacity, compatibility with additional panels, and any possible changes to the system’s electrical configuration.

Here are the major factors that you need to consider:

  • Inverter Capacity: The first and foremost priority factor is to check whether the existing inverter has enough capacity to handle additional power output from the new panels.
  • String Sizing: You need to make sure about the new panels’ compatibility with the already existing string configurations and specified voltage limitations.
  • Cost-Effectiveness: Instead of adding a second inverter to manage new panels, you must measure if upgrading the inverter is a more cost-effective and better option.
  • Compatibility: Most importantly, you should verify whether the new panels are compatible with the existing inverter’s MPPT voltage range. Also, carefully go through the existing inverter’s technical specifications to understand the compatibility in detail.

Remember that consulting a qualified solar professional is very important before you make any upgrades or modifications to your solar power systems.

Ray is an avid reader and writer with over 25 years of experience serving various domestic and multinational private and public energy companies in the USA.

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