Micro Inverters Vs String Inverters: Which To Choose?
The main differences between these types of inverters are:
1️⃣ Each solar panel is fitted with its micro-inverter, supplying the home with AC power.
2️⃣ Micro-inverters are wired in parallel, meaning each inverter runs separately.
3️⃣ String inverters are linked to multiple solar panels, so the entire string is down if one fails.
4️⃣ String inverters are more affordable but generally don’t last as long.
Installation of Micro-inverters and String inverters (Central inverters) is what I’ve been doing and running for the past five years.
Exposure to various micro and string solar inverters places me in an excellent position to share practical knowledge.
So, let’s dive in and explore how these inverters stack up side-by-side.
⚖️ Which Inverter Is Better?
Micro-inverters and String inverters have found their niches in solar applications. Micro-inverters are better for use in applications where smaller systems are required.
String solar inverters are better for larger solar power systems as they’re less costly, reliable, and suited to use with larger solar panels.
Micro-inverters are compact and deliver AC to the home directly from the solar panels. Individual inverters are needed per solar panel, which adds to the cost of the system. A huge positive is that the inverters last as long as the solar panels, which justifies the initial extra cost.
String inverters are hugely popular due to their lower cost and versatility. However, the system is far more intricate to set up and has multiple potential failure points.
But when correctly installed, it is safe and delivers ample power to run the largest of homes. Compatible with grid tie use, battery backup availability, and off-grid use.
🔀 Which Inverter Should You Choose?
String inverters have dominated the solar market for years, mainly because that’s all that was available. Well, things have certainly changed. Micro-inverters and string solar inverters offer pros and cons, which is why they’re both popular options in the solar industry.
The Difference Between A Micro-inverter And String Inverter
Micro-inverters convert the direct current (DC) generated by your solar panels to alternating current (AC) at the one panel where the inverter is located.
The AC is fed down to the home through Standard 12-gauge electrical wires, which connect to the AC combiner box and onto the home’s main board.
Multiple microinverters are linked via a supply cable that combines the power generated by all the solar panels connected to the system.
The energy produced is used to power the home, feed into the grid, or charge backup batteries if fitted.
String inverters couple to strings of solar panels connected in series. Most solar installations across the globe make use of string inverters, especially when battery backup is required.
The quantity of solar panels required is determined by the power needed to power the home.
String inverters use high-voltage DC, which can run into hundreds of volts depending on the system size and require additional safety precautions.
String inverters are often linked to batteries or the grid for extra backup power.
Strings of solar panels are connected in series to the inverter’s solar (PV) input, from where it runs through the MPPT to charge the battery backup or is converted to AC to power the home or push AC back into the grid.
Best Applications For Micro and String Inverters
Most microinverter systems are utilized in grid-tie installations for smaller homes using the grid as backup. Under ideal circumstances, solar panels supply the house with power.
When excess energy is generated, it is fed into the grid during the day and reused during the evening.
If the system is correctly sized and the power generated equals the energy consumed, the actual utility cost should be minimal, if any.
As the technology has improved, battery storage options in the form of batteries have become available for use with microinverters, making them perfect for off-grid or grid-independent use.
String Inverters are best suited for larger solar panel system applications where space for the solar panels and the system hardware is available.
String inverters are available in many sizes and can accommodate the largest solar panels, whereas micro inverter solar panel sizes are limited.
The cost of a solar system plays a significant part in deciding which type of system is suitable. As such, string inverter-based solar cell systems have a lower cost per watt the larger they are.
A more practical solution is a single inverter that runs off and controls the power generated from many solar panels.
How Long Do Micro And String Inverters Last?
Microinverters are warranted for up to 25 years, depending on the manufacturer, which means the initial higher cost of the system is justified when compared to string inverters that generally come with a 5-year warranty, often less.
Microinverters have an IP67 rating and are built to be weatherproof. The inverters are located under the solar panel keeping most of the system hardware outside the home. This enables the installation of the inverters on top of the roof.
Compared to a micro-inverter system, the string system has many more possible points of failure, which makes the string inverter system theoretically less reliable over time.
If the inverter develops a problem, the entire system will shut down, which is not the case with a micro-inverter system.
The vast majority (some are) of string inverters are not weather resistant and thus must be installed indoors along with the batteries, which takes up more space than a micro-inverter-based system.
Inverter Safety
Although microinverters draw their power from DC-generating solar panels, the system’s design is such that the DC feeds directly into the inverter under the solar panel.
The current fed from the inverter to the house is relatively low voltage AC which is dealt with in the same manner as any house wiring circuits.
Microinverters have automatic shut-off circuitry installed that will detect a drop in voltage in a connected circuit and turn off the inverter.
Sting inverters operate within high DC voltage parameters, often between 60V and 450V. Solar panels generate this current. The current is fed to the inverter through the roof using DC-rated wiring and connectors.
Certified technicians must install string inverter solar cell systems as many safety precautions must be complied with to ensure the installation is safe.
Solar Panel Shading
Although string inverters are exceptionally reliable, factors such as shading on one solar energy panel in a string affect the entire series, which reduces solar production.
The whole string will cease production if a solar panel is damaged or a faulty string’s wiring occurs.
Microinverters are well known for their improved energy production in shaded conditions.
PV production can be as much as 25% greater in the shade than standard string-connected solar panels. This is due to the MPPT linked to each inverter and individual solar panel.
During normal sunny conditions, the efficiency of microinverters and string inverters is much the same.
Pros And Cons Of Micro Inverters & String Inverters
The two inverter technologies often go head-to-head when homeowners must decide on a solar panel system for their homes.
Both methods are excellent and provide power to millions of homes around the globe.
The below pros and cons will make a choice a little easier.
| Inverter Types | Pros | Cons |
|---|---|---|
| Microinverter | Simple Installation Inverters and Solar Panels Connected in Parallel Less space is required indoors for the system Easy to expand the system size Optimizer included in the inverter Standard AC wiring Can feed into the grid It comes standard with safety shut-off IP 67 rated 25-Year warranty on premium inverters The monitoring app allows the monitoring of individual solar panels’ performance. Available in 3-phase (split phase) | Higher Initial Cost Limited Battery Options Limits on suitable Solar Panel in terms of Wattage Great for scattered solar panel arrays Excellent panel efficiency at any solar panel positioning |
| String Inverter | Lower Initial Cost Many batteries Storage options are available. Suited to use with large solar panels Multiple inverters and batteries can be linked (increasing the system size) Can feed into the grid Available in 3-phase (split phase) More hardware options. | More Difficult to install More indoor space is required Increased risk (solar panels are connected in series) Less easy to expand the system High DC system 5-Year warranty Generally not weatherproof |
🏆 The Winner: Micro-inverter Vs. String Inverter
The micro-inverter is best for smaller solar systems where each solar panel must perform to its maximum potential to ensure adequate power is produced to run a home.
A string inverter-based system is best for more extensive solar system requirements and where adequate space is available for a more comprehensive system layout.
❔ Other FAQs
Are Micro Inverters More Expensive Than String Inverters?
Micro-inverter-based systems are more expensive initially since multiple inverters are used in the system.
The advantage, however, is that the inverters are warranted for 25 years, significantly longer than the warranties of string inverters that average 5 years for premium manufacturers.
How Do I Choose The Best Inverter For My System?
Several factors will drive the choice of inverter for your system:
- The expected output of the system versus budget.
- Whether a grid-tie system, a system with battery backup, or an off-grid system is needed.
- Available roof size determines how many panels will fit and whether space is available within the home to accommodate a solar system.
- Local weather patterns.
Both microinverters and string inverters vary widely in terms of pricing and quality.
Are String Or Micro-inverters Better?
String inverters and microinverters are both reliable and perform exceptionally well.
A string inverter is the better buy in regions with ample sunshine, sufficient roof space, and where an extensive system is needed.
Micro-inverters are superior to string inverters in more compact homes where space is an issue.
When used in grid-tie systems, micro-inverter systems work superbly. When battery backup is added, the micro-inverter solar energy system is the best choice for the average household.
👣 Next Step
Now that you have the pros and cons and the answers to how microinverters and string inverters differ, the next step is to contact your local solar installer for a system needs analysis.
During the needs analysis process, they’ll determine the system’s required size, enabling you to weigh the cost between a micro-inverter and string inverter-based solar system.
For further solar education, check out our solar inverter knowledge panel.
