WHAT TO KNOW ABOUT SOLAR INVERTERS: String Inverters (Central Inverters), String Inverter with Optimizers and Microinverters

A solar power system is a sure way to save money by significantly reducing or completely eliminating your electric bills.  But before you quickly jump in and purchase a system for yourself, we at Solar Power Supply suggest first to get familiar with some of the technologies involved in a solar power system.  That way, when it’s time to pull the trigger, you’re aware of exactly what you are investing in. 

A solar panel system consists of several parts which include the solar panels themselves, an inverter, the mounts, and optional battery.  A crucial part of the system is the inverter because it is the mechanism that converts the direct current (DC) energy coming from the solar panels into the practical form of alternating current (AC) electricity that we use in our homes and businesses.  You can simply consider the inverter as the engine of the solar power system.  So, let’s check out what an inverter is all about.

There are three types of inverters used today: string, string with optimizers, and micro.  All of them execute the same function in converting DC current into AC, but each one has its own advantages and disadvantages.  

String Inverter

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A string inverter is the most widely used by solar installers today due to its simplicity and affordability.  The wires from the solar panels are connected in “series” from panel to panel, with the last wire connected to the inverter.  The DC power travels through the length of chained wires and into the inverter where it’s transformed to usable AC electricity from 110V-220V.

Advantage:  Today’s advanced string inverters incorporate the latest technology for increased efficiency and are suitable in most home applications.  A string inverter is also much easier to install and maintain because it is usually only one unit and positioned on the ground level, often installed near the property’s main electrical panel whether it’s indoor or outdoor.  When it comes to servicing, string inverters can be quickly accessed and if needed, can be swapped out extremely fast.  No need to go up to the roof at all, which is a big advantage especially if a home has fragile tile or aluminum roofing.  And, out of the three choices here, they have the lowest cost making it more affordable for homeowners. 

Disadvantage:  However, there are some drawbacks to string inverters since they can only optimize energy output on the string level.  So, if a home/business is prone to partial shading from trees, buildings or certain conditions such as cloudy weather, they might not be the best choice.  Any type of shading lowers the output of power from the solar panels, and because they’re strung in sequence, lowers the overall output production of the inverter.  A solar panel within the string that may not be functioning properly can hinder or totally stop power production altogether. Another disadvantage of a string inverter is the inability to expand an existing system without having to change the inverter.

String Inverter with power optimizers

Inverters String Optimizer 01

A system using a string inverter with optimizers is a hybrid between string and microinverters. With this type of inverter setup, optimizers are installed with each panel so unregulated power from the solar panels is conditioned before reaching the inverter.  The use of optimizers also allows for monitoring system performance at the panel level.  Check out this video explanation of optimizers from Solaredge.

Advantage: Having optimizers on each panel enables DC power to travel freely to the inverter on an individual level.  The optimizers control output at a steady state before it’s fed into the inverter. That means shading isn’t as big of an issue.  In this case, highly functioning and performing solar panels within the system are not influenced by less productive ones.  If a panel is not performing, then the panel can be quickly swapped without disrupting the functionality of the other panels.  This is a big advantage of string inverters with optimizers and results in increased efficiency and optimal power output.  With the optimizer option, it can also be easier to expand a system.   

Disadvantage: Using this method does have the drawback of higher cost and longer installation process.  Also keep in mind that power still isn’t converted at the panel level. In addition, although rare, optimizers add another layer of components to deal with when an issue arises with a system.      


Inverters Micro 01

Microinverters are gaining more ground in usage due to its efficiency and conversion at the panel level. They are small devices that get installed directly on the back of each panel and don’t require a string inverter since the DC to AC conversion happens directly from the solar panels. They work independently from each other and are unaffected by the performance of the other panels.   

Advantage: This method of conversion is ideal for systems that encounter shading.  There’s also less resistance with microinverters because DC power produced by the solar panels does not have to travel through wires at great lengths.  At the same time, there are no other components that affect the conversion since it takes effect literally right at the back of each solar panel.  Compared to string inverters, higher efficiency of up to 15% can be expected since shading doesn’t affect other panels involved in the system.  And, if there’s an issue with microinverters, it minimizes any downtime with a system since they’re working independently.  A quick change of a microinverter can be done easily. Another plus to this method is monitoring which occurs at the panel level. A great video explanation can be found on Enphase, the most popular microinverter brand today.

Disadvantage:  As good as microinverters are, there are also drawbacks.  One is its much higher price.  The use of microinverters can add 10%-15% more to the overall price of a solar power system.  Secondly, troubleshooting the system has to be done at the roof level.  If there’s an issue, technicians must get on the roof, and it can be problematic if the roof type is fragile such as tile, slate and aluminum. 

Now that you have the scoop on inverters, you can make a wiser decision on which one works best for your particular needs and budget.  If you still need more information on inverters, the staff at Solar Power Supply will be happy to go through them in detail.  Just know that all of them work great in producing clean and more affordable power that you can easily get from the sun.  Let’s get you started in Going Solar.

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