What is an inverter and how does it work: Handling the power of the sun

While solar panels are the key part of a home solar panel system, they are not the end of it. To be precise, the energy they produce isn't all that useful for your home — not yet, not by itself. To power everything you need a solar inverter. Why you would need it, what it is and how it works — it's all here in this article.

Solar inverter works as DC-AC converter

So what is an inverter? PV modules use the energy coming from the sun and turn it into direct current (DC). It can power lighting in your home and chargers for small devices, like a smartphone. But most home appliances function on alternating current (AC). This is where the power inverter for a home system comes into play: it turns direct current into alternating. The efficiency of an inverter is close to 100% but some energy always gets lost in the process


Average efficiency of grid-tie inverters

All the functions of an inverter in a system can summarized in a list: 

  • DC-AC conversion. The inverter makes current from solar panels usable for home appliances. 

  • System monitoring. The inverter reports on how well your system is performing. 

  • Grid interaction. The inverter sends electricity into the grid, allowing the net metering to occur. 

  • System protect. In the case of electrical arks, the inverter shuts down the system to prevent damage. 

  • Performance optimization. The inverter tracks the voltage of panels and identifies the optimum operational power for the whole array — it’s the same principle of maximum power point tracking as in MPPT-controllers for batteries.

Inverter types vary in price, efficiency and purpose

There are several types of PV inverters suitable for different budgets, energy needs and panel systems. Also it's important to understand whether you are planning to go off the grid with your system or stay connected to it.

String solar inverter works well for panels without shade

String solar inverters are the most widespread type of inverter around the world.  2020, in 2019 They occupied more than 60% of the whole market in 2019, according to IHS Markit. String inverter is grid-connected and can take care of a row of solar panels, which are considered as one string.

The main disadvantage of a string inverter is its inability to cope with problematic panels: if even one panel in a row suffers from shading or is damaged and has lower efficiency as a result, it usually drags down other panels in a row to its level. However, string inverters are relatively inexpensive and reliable, which probably explains their popularity.

Some models have advanced features that make interaction with the device so much easier. Take Fronius Primo 6kW – it has dual powerpoint trackers, Wi-Fi interface for seamless monitoring and a specialised online platform. If your installation is large, it is possible to use multiple string inverters.

The problem with decreased efficiency of the string inverter can be solved through addition of power optimizers. They go on top of the roof next to panels and minimize the effect of the "weak" panel on the string. They, however, don't convert DC to AC themselves. This can be a fine choice for those who aren't ready to buy more expensive microinverters, but still want to maximize the efficiency of their system.

Central inverters can be considered as solely standing type, but it is essentially still a string inverter, just a larger one, which can handle more strings. Strings aren't directly plugged into the inverter in that case, but instead go to the combiner box, and from there DC passes into the inverter. These inverters are used in large-scale solar panel systems.

Microinverters are expensive but efficient

Microinverters are more popular in America than anywhere else. This type of converter is installed directly on a panel, so that DC turns into AC right on the spot. It is a good choice when your panels are subjected to shading, because weak performance of one panel doesn't affect others as it is the case with string inverters. Microinverters make a system more efficient, don't occupy a lot of space, but are more expensive.

Robert van Keulen
Product Marketing Manager at Growatt

The biggest benefit of microinverters is that they have one MPPT tracker for each solar panel. So if one panel is in the shadow, it will not affect all the other panels. The performance of modules is higher when paired with microinverters. Besides, you can monitor each solar panel individually.

You might have already seen AC solar panels for sale on the market from brands like Panasonic. An AC solar panel comes with a pre-installed microinverter.

Battery and off-grid inverters ensure your power backup

If you are using batteries as a part of your system, they might need an inverter on their own, which is called a battery inverter. They come in different shapes and sizes and perform the same function as solar inverters — take the DC from batteries and turn it into AC.

If you plan to use batteries and have a power storage in case of blackout, it might be a good idea to invest in a hybrid inverter which can work both with a battery and panels at the same time. You can even go for multi-mode hybrid inverters, the latest development, which can function both on- and off-grid. If you want to know more check out our article on on-grid, off-grid and hybrid solar systems.

Make sure inverter fits your system

The size of a solar inverter is usually measured in Watts. When purchasing an inverter, you have to make sure it suits the size of your solar panel system. If your solar panel array has a combined power of 5kW then a 5000 W inverter should be just right for it. Consult with the manufacturer when in doubt and read the guidelines. Keep in mind, that if your inverter is not sized properly for your system, in case of malfunctioning you might not be able to get compensation through the warranty.

Vasilii Smirnov
Solar Installation Expert

It’s a common practice to oversize your inverter slightly. For example, if you have a 6-kilowatt solar system, you can get by with a 4,000-5,000-watt inverter. The actual production of your solar panels will rarely match the DC rating of the PV array — usually, it’s about 20-25% less. For this reason, a smaller inverter can be a reasonable pick.

It's hard to predict how much exactly an inverter is going to cost you. Prices for the most simple models start from 500$-750$ and go up to several thousands — depending on the type, properties and functionality of the model.

Inverters come with different warranties of up to 25 years. A good warranty is especially important for an inverter as it is the most fragile part of the system: inverter is a complicated device, but is often placed outside where it's subjected to different weather conditions, swings in humidity and temperature. If possible, it is best to place an inverter in a garage or in another sheltered location, where it's safe from rain, snow and direct sunlight.

Article updated May 2024

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Andrey Gorichenski
Senior Editor

Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.

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