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. What is a solar inverter, why you would need it and how it works — it’s all here in this article.
Key takeaways
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.
90-95% — average efficiency of grid-tie inverters
What does a solar inverter do? 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 protection. 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.
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.
Fronius Symo 10kw Inverter FRO-SA-10-3-208240L Advanced
Pickup on Wed, Jan 22 from Joliet, IL
Delivery on Jan 27–30
String solar inverters are the most widespread type of inverter around the world. They occupied more than 60% of the whole market in 2019, according to IHS Markit. A 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 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 – 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.
SolarEdge S Series Optimizer rated for 440W/60V SE-S440-1GM4MRM
Pickup on Wed, Jan 22 from Millstone, NJ
Delivery on Jan 27–30
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 minim\ize 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 a solely standing type, but it is essentially still a string inverter, just a larger one, that 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.
Enphase Ensemble IQ8 Plus Microinverter Residential
Pickup on Wed, Jan 22 from Millstone, NJ
Delivery on Jan 27–30
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 the 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.
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 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.
SMA Sunny Boy 3.8 Inverter Smart Energy SMA-SBSE3.8-US-50
Pickup on Wed, Jan 22 from Joliet, IL
Delivery on Jan 27–30
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 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.
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 5 kilowatts then a 5000-watt 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.
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 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.
When choosing a solar inverter, you need to consider both its price and service life.
The cost of a solar inverter depends primarily on its type, size and brand. When it comes to string inverters, pure sine wave ones are typically more expensive than modified sine wave inverters because they are more complex. A system made with microinverters is going to be more costly than a system with a single string inverter.
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 thousand — depending on the type, properties and functionality of the model. Inverters come with different warranties of up to 12 years.
Solar inverters generally last between 10 to 25 years, depending on inverter type, manufacturer quality, operating environment, and maintenance. String inverters, common for residential systems, usually work for 10-15 years, while microinverters can last up to 25 years. Proper installation, regular maintenance, and monitoring performance can help extend their lifespan.
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.
Find the one inverter that fits your system
We offer string inverters and microinverters for all kinds of solar installations.
Andrei has been a news editor and freelance writer for a number of medias before joining the A1 SolarStore. Climate change and its impact on people's lives have always been among his interests and it partially explains his degree in Philosophy and Ethics.
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