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How To Best Evaluate String Inverters And How They Work

Solar energy systems are very cost-efficient on your electric bill but can also be confusing. If you’re considering string inverters for your solar panel system, it helps to understand how they work. This article demonstrates the basics of string inverters and how they differ from other solar power systems.

What are String Inverters?

String inverters connect multiple solar panels to produce more power or to increase the voltage. They are also called central inverters and are usually installed in a central location. String inverters can work with or without batteries.

String inverters can power a home or business. Still, they’re not as efficient as microinverters because they require more wiring and an additional box that houses all of the electronics needed for converting DC electricity into AC electricity.

Principle Working of a String Inverter

The principle working of a string inverter is very simple. It converts DC power to AC power by employing a three-phase switching mode power supply. This type of inverter can be connected in parallel to the solar panels, which are placed on the roof of your house, and then connected to your battery bank. 

This way, you can use the AC and DC generated by these solar panels. Grid-connected inverters come in three primary categories: micro, string, and central. Since string inverters are the most common type of residential and small-scale business installations, we will only be concentrating on them today.

The fundamental component of the entire solar system is the grid-connected solar inverter. It transforms solar panels’ direct current (DC) into alternating current (AC), which powers the home and feeds any extra energy back into the grids.

 A 50Hz low-frequency transformer can be found in a conventional inverter. It switches DC on and off in two directions using power semiconductors (such as MOSFETs), producing an AC sine wave. After that, an inductor filters it to alter the AC wave’s form

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The two primary forms of modern string inverters are high frequency (HF) and transformerless (TL). The HF inverter using a DC boost circuit increases the voltage supplied by solar panels to a constant higher voltage.

After that, a high-frequency transformer receives it before changing it at a high frequency (such as 16 kHz). The rest resembles a typical inverter. The TL inverter employs more recent technologies.

As the name implies, it lacks a “genuine” transformer. It converts DC to high-frequency AC, back to DC, and lastly to 50/60Hz standard frequency AC before providing to homes and the grid using a computerized multi-step process using just electronic components.

Different types of inverters
Different types of inverters on display

Advantages of High Frequency and Transformerless

The advantage of the TL inverter is the benefit of not having a “real” transformer, making it lighter, smaller, noisier, and, most significantly, more efficient (no energy consumption through a transformer). 

It makes it possible for two entirely different systems to be installed on the roof. This means that even if one component of the roof system fails, the component will still continue generating power

The advantage of HF is that despite being heavier and less efficient than other materials, HF is still a highly popular option for smaller home solar systems. It has been tried and proven for decades. It is also safer than TL inverters because of the electrical isolations included in the inverter itself.

When evaluating an inverter’s functionality or quality, we typically start by looking at its brand, type, IP rating (how well it can withstand weather conditions when used outside), communication, availability of dual MPPT, efficiency level, warranty, etc.

In essence, they’ve created a printed circuit board that generates an I-V curve comparable to what solar panels generate. Most importantly, it includes five knobs that allow it to change its curve to replicate various solar I-V curves in various scenarios. In essence, testing equipment makes it convenient to conduct several tests in a single lab.

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Read More: What Is a Solar Power System? 

How to Evaluate String Inverters

Before you buy a string inverter, there are several things you should consider. Firstly, look at the efficiency rating of the string inverter. This rating tells you how much power is lost in the conversion process and should be as high as possible for your application. 

The second thing to look at is warranty length and coverage. Any product must have a warranty covering parts and labor for at least five years.

So that if anything breaks down or fails over time due to normal use, You can repair and replace it without purchasing an entirely new unit.

Finally, consider size (height) and price when choosing an appropriate string inverter for your home or business needs!


You can calculate Efficiency as power output divided by input power or, in other words, how much energy you get out of your electricity versus how much you have to put in to make it. To calculate efficiency, we need to know three things: 

  • The total operating time of the device, 
  • The operating cycle of the device(on/off), and
  • The power consumption at full load (full load wattage).

You can measure efficiency in many ways, including full load, peak, average wattage, and annual energy production. The measurement depends on how often your device will be turned on/off in a year.

Size of the Inverter

The size of your inverter is a key factor in determining how much energy it can produce. If you have a large string of panels, you likely need a larger inverter to use all the power they generate.

Similarly, if you have multiple strings of panels grouped on your roof or in one location, this will require a larger residential system (or commercial).

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As well as handling more panels at once, larger inverters are generally more efficient than smaller ones. This means they are significantly cheaper to run and will last longer before needing maintenance or repair work. 

However, smaller units might be cheaper for smaller systems because there won’t be any extra costs during installation or maintenance. However, these savings can easily cause low-efficiency levels, which means that they may not produce enough electricity to serve the right purpose


Warranties are important. Some manufacturers offer a 10-year warranty, others offer a 25-year warranty, and others offer a lifetime or 25-year power performance warranty.

Warranties are important factors in the overall price of solar power systems. This is because they affect your return on investment.

The longer your system is under warranty and working, the more likely you will be happy with your investment.

Your ROI depends on how much electricity you produce over time. This compares to the installation requirement of the solar array. This is in addition to any other costs of owning and operating a PV system. For instance maintenance, repairs, or replacements of damaged components over time due to vandalism, theft, etc.


The price of a solar panel system is one of the most important factors to consider when buying a system. You want to buy a system that will provide you with the most power for your money, but don’t buy a system that’s too small or too large for your needs.


In a nutshell, string inverters are energy efficient and highly cost-effective. They allow you to take advantage of solar energy in an easy way to install and operate.

Unlike nonrenewable resources like fossil fuels like oil and coal, which run out over time (and have side effects), solar panels produce free electricity daily thanks to their ability to convert sunlight directly into electricity with zero emissions or pollutants. 

With the right equipment installed on your property—such as photovoltaic panels or solar water heaters—you can take advantage of this abundant resource whenever possible while reducing your carbon footprint simultaneously!

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