Everything You Need to Know About Microinverters (2022)
Here’s what this article will cover:
- What are microinverters?
- String inverters vs. microinverters
- Advantages of microinverters
- Popular microinverters
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What Are Microinverters?
Microinverters are small electronic devices that convert direct current (DC) into alternating current (AC). One microinverter could fit the palm of your hand. The main factor differentiating microinverters from traditional inverters is that they operate at the panel level rather than the solar panel system as a whole.
Microinverters are categorized as module-level power electronics (MLPE). Therefore, they have much smaller power ratings — just enough to convert a single solar panel’s DC power into AC power.
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, meaning you can install it on a solar panel with a minimum of 235 W and a maximum of around 440 W power output.
Most microinverters are plug-and-play devices, meaning you can connect and operate them in a few easy steps or disconnect them without using much time or tools. They usually sport built-in MC4 connectors for quick and easy connection. They also come with remote monitoring technology, meaning you can check the status of each microinverter, and hence the performance of each solar panel, on a smartphone app.
String Inverters Vs. Microinverters
The major difference between string (or central) inverters and microinverters is the number of solar panels they connect to. Traditional inverters connect to an entire solar array or string, which can be anywhere from a couple of panels to hundreds. On the contrary, microinverters are connected to each solar module and are usually mounted on the racking system.
Traditional inverters are bigger and bulkier, making them difficult to carry and install. Microinverters are much smaller, slightly larger than the junction box on a solar panel, and weigh around 2-4 lbs.
Microinverters typically cost a couple of hundred dollars per unit. While they offer many advantages, which we will cover further, microinverters are notably costlier than string inverters when installed on an entire solar power system.
Check out this video from Enphase to learn more about microinverters and their benefits.
Microinverters Vs. Power Optimizers
DC power optimizers are physically identical to microinverters and also connect to the back side of a PV module. Where they differ from microinverters is their functionality.
Power optimizers do not convert DC into AC. Their job is to monitor each panel. This way, a system with a combination of a string inverter and power optimizers acts as a hybrid between a simple string inverter system and a microinverter system.
Being similar to microinverter technology in some ways, optimizers are also classified as module-level power electronics (MLPE). In addition to monitoring output, power optimizers can also sense when a panel is not generating enough power, due to shading or other reasons.
When this happens, the optimizer can “optimize” the output so that the entire string is unaffected. Therefore, just like microinverters, optimizers can be a helpful addition to any system installed on a complex roof with poor panel orientations.
Advantages of Microinverters
Despite their added cost, microinverters are rapidly gaining popularity thanks to their numerous advantages. Let us go over some of them:
Lowered Chance of System Shutdowns
The greatest advantage of microinverters over traditional inverters is the drastically lowered chance of a system shutdown.
If a string inverter fails, your system will be unable to provide your home with any AC power, rendering your solar panels useless. For relatively larger systems, this could cause huge losses from power wasted while waiting on a technician to repair the issue.
On the contrary, if one or two microinverters fail, the remaining panels in the system keep functioning. Since microinverters are plug-and-play devices, it is easy to swap them for a newer unit within a few minutes.
If a single panel stops working in a system with a string inverter, the entire system shuts down. You’d then have to go onto the roof and check each individual panel for errors — an inefficient process.
Microinverters provide panel-level monitoring, meaning you can always tell which panel is underperforming, allowing much easier troubleshooting.
Most modern string inverters also allow limited system monitoring on the string or array level. This means you can identify a failing string, but identifying non-operating panels is impossible remotely. DC optimizers can add panel-level monitoring features to a system with string inverters. However, that adds enough to the system cost that you might as well stick with microinverters.
No Sizing Restrictions
String inverters have defined input and output specifications, meaning you can only have a specific number of solar panels connected to a single string. If installations become too complex, then wiring your array can become difficult.
For example, an inverter with a DC input of 360V should have six panels connected in a line. If your roof only has space for rows of four panels, you’ll need longer cables and connectors. This may increase the complexity of installation and even reduce your system’s efficiency.
With microinverters, every inverter works at the panel level, eliminating string-size restrictions. You can also arrange them in virtually any layout without additional complexity or expense.
Systems with central or string inverters are much more sensitive to fluctuations in the output of individual panels. This means that systems with traditional inverters are only as powerful as their weakest panel.
For instance, if one panel in the string stops generating power when covered by shade, the power generated by the remaining panels can only match the output of the worst-performing panel. Microinverters ensure that you’re harnassing the maximum power per panel, avoiding wasted energy.
This is also helpful on uneven or complex roofs, as microinverters maintain maximum efficiency regardless of arrangement.
Most string inverters on the market come with a 10- or 12-year warranty. Modern microinverters last much longer and even come with 25-year warranties, matching the lifespan of most modern solar panels.
Since replacing a central inverter can be pricey, microinverters make an excellent case for long-term value.
Microinverters are a great choice from the installer’s perspective too. Traditional inverters are large, bulky objects that are difficult to carry and install.
Microinverters solve this problem by being much smaller; they are not just easy to carry but also connect. Most technicians can install a microinverter within a minute or two.
Ease of System Expansion
Imagine you installed a 3 kW solar system with a 3 kW string inverter. If your energy needs increase and you want to add another 1 kW of panels, it is difficult to expand your inverter capability.
In the case of microinverters, however, you can easily add solar panels without worrying about the compatibility of other components.
While the idea of microinverters goes back many decades, the device itself only took physical form in the last 15-20 years. California-based Enphase Energy was the first major company to fully invest in microinverter design and production. It launched the M175 microinverter in 2008, and with many advanced models has shipped over 45 million microinverters to date.
Currently, its IQ series comes in multiple, compact single-phase microinverter models with modern features such as smart monitoring, rapid shutdown and the industry-first Application-Specific Integrated-Circuit (ASIC) technology that allows the Enphase microinverters to operate in grid-tied as well as off-grid conditions.
Besides Enphase, SMA is a renowned brand that used to offer microinverters. However, it does not sell the product anymore. Over the years, a number of microinverter companies have opened up in the U.S. The market, however, is dominated by the Enphase IQ series.
APsystems currently claims the spot for the second largest supplier of microinverters worldwide. Its unique multi-module microinverters can be connected to two or four solar panels at a time, and even have an in-built MPPT (maximum power point tracking) controller for systems with energy storage. Some solar panel brands also offer AC modules, meaning they have microinverters integrated into the panels as default. SunPower is one such example — it uses microinverters produced by Enphase.
Let’s take a look at the top few microinverter models available today:
|Microinverter Model||Peak Output Power (STC)||Warranty Length||Cost||Key Features|
|Enphase IQ7 microinverters||250-366 VA||25 years||$145-$194||Built-in rapid shutdown|
|Enphase IQ8 microinverters||245-384 VA||25 years||$166-$242||Application Specific Integrated-Circuit (ASIC),
panel-level remote monitoring
|APsystems DS3||250-660+ W||30 years||$176.56||2/4-panel connectivity,
|APsystems YC series||250-1100 W||10 years
(+15 years optional)
Should You Use Microinverters in Your Solar System?
Over the past decade, microinverters have been touted as the next big thing in solar PV inverter technology, and swift adoption has shown that they are here to stay. Whether you should choose a traditional, single inverter or go with microinverters depends on several factors. For instance, if you have a roof that is not ideal for traditional system layouts, using microinverters will provide you with a faster payback period and more savings over the lifetime of the system.
On the other hand, if you want a simple system installed in the most cost-effective way, you can opt for a high-quality string inverter from SMA, Fronius, SolarEdge or similar brands. You can also explore the option of adding power optimizers to a string inverter system and save some money. If you are going with newer solar tech like solar shingles, you will not be able to avail the benefits of microinverters.
The best way to find out what type of inverters are best for your solar array is to consult with a local solar company near you.