Micro-Inverters Vs. String Inverters: A Comprehensive Guide
By Aniket Bhor on in How Solar Power Works
Virtually no solar power system is complete without an inverter. People even compare the importance and functionality of a solar inverter with that of a heart. It, therefore, becomes mandatory to take a look at the evolution of such a crucial component - which brings us to the comparison of traditional, string inverters with the more advanced microinverters!
For almost a decade, microinverters have been one of the fastest-growing segments in the PV industry. Many experts even believe that it is a matter of time until they replace string and central inverters entirely.
But how much sense do microinverters make today? Should you go with regular, string inverters or spend more on microinverters? Let us dive into a detailed analysis and find out.
What Are Microinverters?
“Micro” is used to signify something that is very small. Microinverters, therefore, are tiny inverter units that can even fit in your palm, weighing around a kilogram per unit. When everything from TVs to computers is becoming slimmer and more compact, why should inverters stay behind?
Each microinverter is connected to an individual panel and converts the direct current (DC) generated by the solar panel into usable, alternating current (AC).
An increasing number of brands are also offering what they call “AC solar panels”, which are basically solar panels with integrated microinverters, so that the power flowing out of the panel is AC power, eliminating the need for a string inverter.
Since they are installed near or directly on the solar panel, microinverters are categorized as module-level power electronics (MLPE). The power rating of a microinverter is comparable not to the string or the system itself, but to the power rating of individual solar modules.
For example, a typical Enphase IQ8+ microinverter is rated for a peak output power of 300 VA and an input power of 235-440+ W. This means you can install it on a solar panel with a minimum of 235 W and a maximum of around 440 W power output - making it suitable for most solar panel sizes.
Now that you have an idea about microinverters, let us go ahead and compare them with the longstanding, tried and tested string inverters.
String Inverters Vs. Microinverters
The increasing popularity of microinverters is proof that they offer a number of advantages over string inverters. And yet, millions of string inverters are still purchased and installed worldwide. So which one is better for you, and how? Let's find out.
1. System Downtimes
When a string inverter fails, there is zero watts of power received from the entire string. This means until a technician arrives and fixes the inverter, your system is of no use.
Microinverters, on the other hand, work at the panel level. So, if a single microinverter fails, just one solar panel stops generating power. Additionally, a microinverter can easily be swapped for a new one, reducing the panel downtime even further.
2. Panel-Level Monitoring
Most modern string inverters come with WiFi connectivity and remote monitoring features. You can view the status of your system from your living room couch, or for that matter, anywhere in the world. However, you can only monitor your power generation at the system level. If one or two panels malfunction, it is likely that you won’t notice.
Many microinverters come with remote monitoring but at the panel level. You can see how much power every single panel is generating, so if one of the panels is producing seriously low power, you will be aware of it.
3. Performance
With string inverters, the entire string acts as one large solar panel. Therefore, even if a single solar panel in the string is performing poorly, the production of the entire string falls.
With micro-inverters, all solar panels are connected and yet operate independently. This means that if one or more panels are shaded or do not receive sufficient direct sunlight, it will not affect the panels that are not shaded.
For homes that have complex roof layouts where every solar panel cannot receive sunlight at the desired angle for the entire day, microinverters are a perfect solution.
4. Simplicity And Compactness
Microinverters are a great choice from the installer’s point of view as well. It can often be difficult to carry and install a traditional, bulky string inverter.
Microinverters are light and easy to carry. Additionally, they are designed to be plug-and-play devices, meaning they can be installed within a few minutes.
5. Sizing Restrictions
Suppose you installed a solar power system with a string inverter, and in a few months or years you decide to purchase an electric car. You want to charge your EV with solar power, and hence need a larger system. If you have a string inverter, increasing the system size is going to be complicated, and you may have to spend more than the ideal amount.
With micro-inverters, you can even increase the system size easily - whether it is just a few hundred watts or a few kilowatts. Therefore, microinverters are a preferred choice if system expansion is an option in the near future.
6. Lifespan
While string inverters perform efficiently for 10 years, microinverters can boast up to 20 years of excellent performance.
Overall, microinverters are simply more reliable and more durable.
7. Cost
Here is one area where string inverters beat microinverters. Despite the lowered cost of microinverters in the past few years, they still are significantly expensive when compared with string inverters.
For instance, a typical string inverter in New Zealand may cost about $2,000. A set of microinverters, on the other hand, can cost an extra $1,000-$1,500 for a similar-sized system.
Microinverters Vs. Power Optimizers
When speaking about Module Level Power Electronics (MLPE), there is one technology that promises some of the benefits offered by microinverters, without breaking the bank. Power optimizers are small units attached to individual solar panels, which “optimize” power production at the module level.
Unlike microinverters, power optimizers work in addition to string inverters. Power optimizers allow you to monitor each module separately. They can even “optimize” the power output when one or more panels are shaded.
This way, DC power optimizers act as a hybrid choice that sits between microinverters and string inverters.
Popular Micro-Inverters Available in New Zealand
The market for micro inverters in New Zealand is almost entirely ruled by Enphase. California-based Enphase Energy is the pioneer in microinverters, and the largest selling brand worldwide. The company’s IQ series of inverters is universally lauded as one of the best microinverter series.
The IQ series offers multiple single-phase models with modern features such as smart monitoring, rapid shutdown, and the novel Application-Specific Integrated-Circuit (ASIC) technology that allows the Enphase microinverters to operate in both grid-tied and off-grid settings.
In 2016, Enphase opened a high-tech R&D facility in Christchurch. The company even launched their highly-rated IQ battery in NZ a few years ago. Today, Enphase products are available with several solar installers nationwide.
Some installers are also offering micro inverters by APSystems. APSystems is another American brand of microinverters that is rapidly gaining popularity. The second largest supplier of microinverters worldwide, APSystems products are smart, efficient, and cost-effective.
Conclusion
The concept of microinverters is nearly 50 years old, but the technology started catching up about a decade ago. In the last few years, microinverters have taken the industry by storm with clear advantages and reduced pricing.
The simplicity, increased performance and reliability, and better lifespans make microinverters a clear winner when compared with traditional, string inverters. And yet, they are still expensive enough to discourage many people from choosing them.
So, should you buy microinverters? The answer to this question depends on a few factors. If you have a sufficiently large roof with a north-facing slope, you may get a solid power production even with a string inverter system. But if you have a complicated roof where some panels receive slanting rays, or are shaded for some part of the day, then it would be best to choose microinverters.
Also, if the budget is not a constraint, and you want the absolute best with your system, then again, solar micro inverters are for you.
Get 3 Free Solar Quotes now to compare the price and performance of inverters offered by solar installation companies in your area.