T

he market is full of solar panel options, so picking the right one can be a baffling task for many. But the challenges don’t end there: all components must be chosen with equal care if you want your modules to last and produce the maximum output possible.

The hardware you will have to buy on top of the panels is sometimes referred to as the “Balance-of-System” or BoS. It includes racking, a special energy meter, performance monitoring equipment, a battery, etc. Today we focus on solar inverters - the operational brains of any solar system - and examine why microinverters for solar panels are considered a better option.

What are solar inverters, and how do they work?

To begin with, let's clear up what a solar inverter actually is. As you know, photovoltaic panels collect sunlight and convert it to electricity, which we use later to power our homes. However, the electricity solar modules produce can’t be directly used to run our domestic appliances.

The thing is, electricity comes in two types—alternating current (AC) and direct current (DC). They were seen as competing technologies in the 1880s during the big dispute between Thomas Edison and Nikola Tesla, known as the War of the Currents. Today, however, these two forms of electricity are used for different purposes and are both essential to support our daily living.

Solar panels produce direct current due to the nature of the photovoltaic effect. This effect occurs when sunlight excites the electrons within a solar cell, and they start to flow continuously around the circuit. That flow only goes in one direction, which is why the current is called direct. Apart from solar panels, DC is used in almost all electronic equipment, hybrid and electric vehicles, flashlights, and more.

In alternating current, the electrons don't flow in one direction. AC is created by switching the potential between positive and negative terminals in a fixed amount of time, forcing the electrons to reverse their direction periodically. Alternating current is much easier to step up and down in voltage and distribute over large distances with minimum power losses, which makes it perfect for electric transmission networks. For that very reason, most of our home appliances are designed to receive AC electricity.

We have to change DC into AC to make power generated by solar panels suitable for our homes. This is where we need an inverter -  a PV system component that transforms the direct electricity produced by the panels into an alternating current. Without this piece of equipment, we wouldn’t be able to make use of our photovoltaic system.

So how exactly is DC changed to AC? While direct current moves in a straight line, the alternating current would be displayed as a sine wave. The inverter produces vibrations at a definite frequency through the electric circuit, amplifying the current magnitude to the necessary level so that the output closely matches the true sine wave of the alternating current.

Micro and string inverters for solar panels

There are two main types of inverters. The first type is a string inverter – a standalone device typically installed near the main switchboard. It is linked to several “strings” of panels and aggregates the DC output from all of them to convert it to AC. One string device can handle multiple strings attached to it, and this number depends on its size in kilowatts and the wattage of your panes.

Another solution is a system of miniaturized inverters installed under each individual panel on the roof. They receive all the available output from each panel, convert it to AC immediately on the spot, and then send it to your electrical panel board.

Despite being the older and less efficient technology, string options hold the largest market share globally. However, multiple small inverters are gaining popularity and often appear to be a more reasonable choice. Further on, we'll explain some of their benefits and drawbacks in detail.

Advantages of microinverters

Shading mitigation

Solar systems based on multiple compact inverters are much less sensitive to partial shading. Photovoltaic panels are usually placed in such a way as to collect maximum unobstructed sunlight, but sometimes it’s not possible. In that case, installing a string converter would mean significant power losses. If just one cell is partly shaded, the output of the others will be equally affected: the electrons in a shaded cell stop moving, which disrupts the energy flow in the entire system.

Small on-roof inverters, by contrast, are perfect for systems with partially shaded panels. They are connected in parallel, meaning each panel generates its own voltage and current. So if one module underperforms, this won’t affect the other ones.

Solar panel-level monitoring

String options typically offer only string-level monitoring, meaning you can identify a faulty string but can’t tell which module is to blame.

Mini inverters allow you to monitor each solar panel individually and quickly notice if one of them underperforms. This feature ensures much easier upkeep and troubleshooting.

Solar system scalability

Another big advantage is scalability. If you decide to expand your solar system (i.e., after adding a large storage system), you can simply add new panels. In fact, you can scale your photovoltaic system almost infinitely.

Alternatively, a string device gives much less flexibility. It can handle only a certain number of modules, so you must purchase a separate large box for every few panels you wish to install.

Longer lifespan

The average lifespan of photovoltaic panels is between 25 and 30 years, but string inverters tend to last much less. Their life averages 10 to 15 years, so you will likely have to replace yours at least once. Small on-roof systems last just as long as the panels without causing you any extra hassle of replacing them.

Enhanced safety

As multiple inverter setups manage power on a smaller scale, they prevent the voltage from exceeding 60V on the roof. By contrast, with string alternatives, the voltage can rise to 1000V, increasing the risks of arc-faulting and fire.

Additionally, on-roof devices offer a rapid shutdown function that can turn off or reduce voltage throughout the photovoltaic system to meet electrical safety requirements.

Disadvantages of microinverters

Cost

The biggest downside is the price tag. Small converters cost between $145 and $242 per unit, so to equip a standard 6kw solar installation, you can expect to pay between $3,500 and $5,800. Meanwhile, a string solution will run you $1,000 to $2,000, which certainly is an advantage given the high cost of solar panels.  

More difficult maintenance

If one of the multiple devices fails, identifying it can be tricky. Additionally, as the converters are placed under each panel, maintenance and repairs require going up on the roof, which is somewhat riskier.

Best solar micro inverters: Enphase & cheaper alternatives

Major manufacturers of miniaturized inverters are Enphase, Chilicon, APsystems, and a number of others. Additionally, some companies offer devices with equivalent features, such as Solaredge power optimizers.

Enphase dominates the market: according to some estimates, the company is close to a 100% market share. However, its competitors also sell unique products worthy of attention. We'll make a quick Enphase vs. peers comparison below.

Enphase

The American company is primarily known as the first manufacturer of solar micro inverters for solar panels. Enphase introduced this technology in 2008 and still retains leadership. Enphase offers two product ranges: the IQ7 series and the IQ8 series.

IQ7 series are the previous generation products launched in 2018. The models from this line were designed for modern high-power photovoltaic systems and are compatible with panels delivering up to 350 watts. The devices boast a maximum output capacity of 240 VA and a peak efficiency of 97%.

Enphase outfitted the IQ7 series with a built-in rapid shutdown to meet electrical safety requirements. However, this feature means you cannot use electricity produced by solar panels during power outages, which is often considered a disadvantage.

Enphase IQ8 series provides a greater choice of specifications to meet different needs and preferences. The inverters are designed to provide a peak output power of up to 384 watts and an efficiency of 97.5%. IQ8 Enphase models can provide backup power during outages, unlike the previous series. This cutting edge technology involves creating a microgrid and preventing electricity from being fed to the utility power system.

Chilicon

The California-based manufacturer offers two flagship models: CP-720 and CP-250E. The first one is designed for use with two high-power panels of up to 420 watts. It delivers a peak efficiency of 96.6% and is compatible with most modules featuring 60 to 128 solar cells. This allows you to install less equipment on your roof, as one device gets attached to two panels.

CP-250E converters are more compact and, therefore, more common for residential systems, with each device supporting one panel up to 420 watts.

Chilicon models generally offer lower input power and voltage than Enphase alternatives. However, a homeowner will barely notice the difference in performance while the price differs significantly. On average, the Chilicon option will cost you about 30-40% less.

APsystems

APsystems produces powerful products for residential and commercial installations. The company’s flagship offering is the YC600 model. Similarly to Chilicon’s CP-720, it uses one device for every two panels. This simplifies installation and brings down logistics costs but makes wiring a little more complicated. YC600 accommodates 60 and 72-cell panels with power ratings from 250 to 410 watts.

APsystems option is slightly inferior to Enphase in terms of performance but commands a much better price. Generally, you can expect to pay around 40% less for APsystems equipment.

Conclusion: micro inverters are usually worth the extra cost

To sum up, if you hold out the possibility of scaling up your solar system in the future and wish to avoid partial shading issues, small multi inverters would be an ideal choice. Those homeowners who would prefer the most advanced and efficient product on the market should consider Enphase solutions, while consumers seeking a less pricey alternative may find Chilicon and APsystems models more attractive.  

Sources:

https://straitsresearch.com/report/pv-inverter-market

https://pv-magazine-usa.com/2022/06/07/enphase-has-shipped-43-4-twh-of-solar-microinverters-to-date/

Posted 
Apr 11, 2023
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