The primary task of solar inverters is to change the direct current (DC) generated by solar panels into alternating current (AC), which is the form of power used in your home.
Over the past few decades, inverter technology has been developing gradually to help homeowners get the most out of their PV systems. As a solar homeowner, both string inverters and microinverters perform this function for you, but they approach the task in different ways.
Let’s examine string inverters and microinverters in more detail and see how they compare when it comes to using them in solar energy systems.
What is a string inverter?
The primary service panel and electricity meter are often located near to a string inverter, which is a standalone box.
Depending on the size of the entire solar power system, each household solar installation may include just one single inverter or as many as two string inverters.
A “series string” of solar panels, also known as a group of 6 to 12 solar panels, is what a string inverter uses to operate in a series circuit. Leading producer of string inverters is SMA.
Advantages of string inverters
Easy to troubleshoot
The main benefit of a string inverter is that only one of them is required to convert the DC electricity produced by your solar array to AC power. The inverter is most likely to malfunction in a solar system, which makes troubleshooting very simple when something goes wrong.
A single string inverter can be installed on a solar panel installation for less money than microinverters. String inverters are more cheap than many microinverters and need less man hours to operate.
Lower probability of wiring mishap
There are fewer connections between the string inverter and the solar panels. Consequently, compared to a microinverter system, there is a lower likelihood that a string inverter configuration will be poorly cabled.
Disdvantages of string inverters
Efficiency in partial shade
Due to the requirement that solar panels be wired in series for string inverters, if the output of one solar panel is impacted, so too is the output of the entire series of solar panels. If a solar panel series has a section that will be shadowed for a portion of the day, this can be a serious problem.
More difficult system expansion
A string inverter must be operating at or close to its peak capacity for best performance. Therefore, if you decide to expand the size of your solar array in the future, those panels will need to be connected to a different string inverter, which will increase complexity and cost.
String inverters are warrantied to last between 8 and 12 years, whereas microinverters have a 25-year warranty.
With a string inverter system, there are no components attached to the back of each panel to perform the necessary function, hence panel-level insight is not available.
You can see the total amount of solar energy produced, but you can’t see if a particular panel is performing poorly because of a crack, a flaw, or other debris.
What is a microinverter?
String inverters and microinverters both serve the same fundamental purpose, however microinverters are put directly beneath each solar panel on your roof. These microinverters are each roughly the size of a router for the internet.
A solar panel installation using microinverters would normally have the same number of microinverters as there are solar panels, which is a significant distinction between them and string inverters (Note: there are microinverters that accept two or four solar panels).
Leading producer of microinverters is Enphase. Since entering the market in 2009, Enphase microinverters have played a crucial role in their rapidly expanding industry. Their scientists have been researching the best ways to incorporate maximum power point tracking (mppt) principles into their parts for increased solar PV output.
Microinverters don’t have this issue because they work in a parallel circuit rather than the series circuit used by regular string inverters, which will cap the electricity production of each panel by the lowest producing panel on your roof.
To the fullest extent possible, a microinverter will utilize the output of each individual panel. It will change the voltage of the grid from the power produced by each solar panel. Each solar panel and microinverter combo is capable of “doing their best” and supplying the maximum amount of power.
Advantages of microinverters
Rapid shutdown capability
Rapid solar system shutdown is required by new electrical rules to protect first responders and firefighters from high voltage when they must work on rooftops or maintain power lines. Microinverters are compliant with these rapid shutdown specifications and each module includes this functionality.
The main benefit of employing microinverters is that you can generate more solar electricity in theory. The minor variations in currents between solar panels are the cause of this. When solar panels are connected in a string, the current is decreased to that of the panel with the lowest output.
Suitability for challenging installation conditions
Microinverters are the best option if a solar system is facing multiple directions, such as some panels facing south, others east, and still others west. Or, once more, microinverters would be the best if you had problems with shadowing from trees or a big chimney.
In these circumstances, the solar panels will produce varying amounts of electricity at various times of the day; however, microinverters will ensure that you capture all of the energy, whereas with a regular inverter you will lose some of this production
Standard inverters normally have warranties of 8 to 12 years, whereas microinverters typically have guarantees of 25 years. A few years ago, there were concerns about the dependability of microinverters, but the industry has caught up with technology, and the long warranties on microinverters reflect the producers’ faith in their goods.
While a typical inverter can only track the production of the entire system, microinverters allow you to track the production of each individual panel.
System expansion ease
Microinverters are easy to add one at a time if you ever decide to extend your system. Your current solar array can easily be expanded by adding each panel and microinverter pair without the hassle of finding a location for and installing additional string inverters.
Overall, microinverters provide value, but they should only be used if you have panels that need to be oriented in many directions, need to comply with rapid shutdown requirements, or have shading concerns. Otherwise, the conventional inverter, which costs less, is usually more economical.
Disadvantages of microinverters
The cost of microinverters is their primary drawback. On a typical 5kW household solar installation, they cost about $1,000 more than a string inverter.
If one of your microinverters broke, it would be difficult to identify which one it was, and if you did, repairing and replacing the part wouldn’t be as simple as sticking a new string inverter on the side of your house.
To restore AC conversion capabilities, your solar installer would have to climb back onto your roof, work with your racking system, remove the solar modules, and replace the microinverter.
Amount of hardware on your roof
Every solar panel on your roof has a microinverter attached, so there is a lot of pricey metal machinery up there.
A microinverter could function as a tiny lightning rod. If your old wooden house has shake roofing materials and you live in a storm-prone area, you might want to reconsider installing them.
Microinverters vs. string inverters: which is best for your home?
The majority of microinverter manufacturers tout extremely low failure rates, however at SolarSystems, we continue to be dubious of these assertions.
The inverter, which is the most intricate electronic component in a solar system, also happens to be the component that fails most frequently, according to my decades-long expertise in the solar installations industry. Instead of installing one string inverter, I would be quite hesitant to install 20 inverters. Only in extreme cases of significant shading problems would I do this.
Although the ability to monitor each panel is marketed as a feature by microinverter makers (and it is), they do not offer the monitoring that enables the user to accomplish this. Unless you agree to purchase the higher level of monitoring as an upgrade, they only permit the installer to see the panel-level data from your system and not you as the client.
This implies that as a client, all of the monitoring data that is displayed to you is information about the system as a whole. A skeptic would counter that they do this in order to shield themselves and their installers from support calls relating to malfunctioning inverters. It is exceedingly challenging to tell if only 1 or 2 out of 25 or so inverters have failed using only system-wide monitoring data.
Despite this, I continue to favor microinverters; but, if I were a customer buying a system that included one, I would fork up the extra cash for the degree of monitoring that provides panel-level analysis. At least the entire system stops when a string inverter fails, and this is obvious.
On roofs, I have a sneaking suspicion that many microinverters have failed but their clients are unaware of it.
String Inverters vs Micro Inverters: Worth Buying? Ratings