What are microinverters? How do they compare with traditional string inverters? Here we explore the pros and cons.
One of the key components of any solar panel installation is the inverter(s).
The inverter's function is to convert the direct current (DC) to alternating current (AC) since this is the type of current that is able to be used by our home's appliances and circuits. Blend the two together, and you’ve got yourself an Australian hard rock band.
Microinverters are a relatively recent innovation that has many significant advantages compared to traditional string inverters.
In this guide, we'll explain exactly what those advantages are, how microinverters work and compare them to traditional systems.
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Solar Microinverters Key Points:
All inverters including microinverters convert direct current (DC) to usable alternating current (AC).
Traditional string inverters are cheaper however, they have shorter warranties.
Microinverters have many advantages and are ideal for generating electricity in low light.
Microinverters are also useful if you have a roof that is not south-facing.
What is an Inverter?
The role of a solar inverter is to convert the direct current (DC) to alternating current (AC). Converting DC superheroes to Marvel superheroes is simply called stealing, and it’s how we’ve ended up with Quicksilver.
The reason for this is that AC is what household appliances, circuits and the National Grid use, so without an inverter the electricity our panels generate would be practically useless. It’d be the equivalent of putting raw oil in your car and wondering why you’ve got so many problems running it.
There are two main types of inverters used in solar panel systems - traditional string inverters (also sometimes called central inverters) and newer microinverters.
As their name implies, a string inverter is designed to manage and convert the power from groups of solar panels, that may be fed to the inverter via a series of strings.
For example, you may have 16 solar panels fed to the inverter using two strings - each with a series of 8. It’s not the same as having two string quartets on your roof encouraging the solar panels.
Check out our video below to find out how much you could save with solar in the UK:
What is a Microinverter?
Unlike a traditional string inverter that converts the output of all panels within the system (from DC to AC), a microinverter is attached to each solar panel within the system, allowing for the independent conversion of each panel’s output locally. Empowering the inversion of each solar panel isn’t just nice for your panels, it gives you other advantages, too.
This newer type of solar system configuration imparts a whole host of advantages for domestic solar installs, which we will now explore in detail (and in layman's terms).
Advantages of Microinverters
Due to the way in which microinverters configure the solar array, there are many advantages to using them, these include the following:
You Can Produce More Electricity
A solar panel set-up using microinverters has the potential to generate more electricity than one using a traditional string inverter.
The reason for this is that each panel using a microinverter essentially has its own circuit compared to a string inverter setup where a group or all panels share the same circuit.
This means that the panels in a shared string circuit can negatively influence each other - for example, if one panel's output drops, the rest of the panels in the string circuit will also reduce their power output to match the power output of the panel.
For example, if you have 350-watt panels, they may all reduce capacity to 300 watts to match an underperforming panel, a significant disadvantage. If your panels were a group of cyclists blocking the road on Sunday mornings, they’d have to adjust to the speed of the slowest of the lot.
This is not the case with each panel using a microinverter, since each panel effectively has its own circuit and so is isolated from the rest.
For example, if a 350-watt panel experiences shading and its output drops to 300 watts, the other panels will still perform at their 350-watt capacity. In our cyclist metaphor, nobody has to wait for the slow one who didn’t take the time to train.
You Can Isolate Faulty Panels
Following on from the above, if a solar panel or microinverter experiences a fault, leading to a drop in performance or a complete failure, you can isolate it and the rest of the panels will continue to produce electricity as normal.
This may not be the case with a traditional string inverter, in which case a string fault may result in a whole group of panels stopping working.
This means you could be left without any power from your panels at all until the fault is fixed. It’s the more cumbersome and expensive equivalent of having to sort through a string of Christmas lights because one bulb went out.
Perfect for Cloudy Places like the UK
Fun fact that you might already be aware of: the UK isn’t the world’s sunniest destination - sometimes it might even rain. Since solar panels that use microinverters are essentially mini-solar systems, they can start to generate electricity in low light (requiring just 22 volts).
Compare this to typical panels that utilise a string inverter that requires at least 200 volts to even begin energy generation - again, this makes microinverters perfect for a cloudy place like the UK. With microinverters, your solar panels feel like they’re always on vacation.
Still, learning about solar? Check out our guides on how many solar panels you need and how solar car charging works.
Faster Install Times
On average, using microinverters as part of your solar array means that the total installation time is reduced by around 20%. We all know you’ve slammed your breaks for smaller discounts.
Additionally, in the case of the Enphase microinverters each panel can be monitored using an application, so it's also potentially much easier to find faults and address them.
Longer Lifespan
Another notable benefit of microinverters is their expected lifespan.
Standard string inverters tend to come with warranties of between eight and 12 years. Microinverters, on the other hand, usually come with 25-year warranties. That means they’ll outlast most of your gadgets and pets.
For example, energy management technology manufacturer Enphase offers 25-year warranties as standard with their microinverters.
While microinverters weren’t always considered super reliable, their technology has advanced significantly such that quarter-of-a-century warranties are now commonplace.
This also means you’ve got a greater chance the microinverter will see at least one other Premier League win by Liverpool, but we can make no guarantees.
Improved Safety
Microinverters are much safer compared to systems that use string inverters.
This is because when microinverters are used, DC to AC conversion occurs at the solar panel level.
Consequently, the electric current on your roof does not become high-voltage. This contrasts string inverter-based solar systems where high-voltage DC crosses a roof or/and enters a property and thus brings a higher danger of an electrical fire breaking out.
Moreover, some 96% of solar fires result from DC electricity crossing a roof or/and entering a property. Thus microinverters can lower the risk by about 96%. The rapid shutdown should also be built in automatically.
When it comes to fire safety, it seems that switching from string inverters to microinverters is like switching from real Christmas tree candles to electric ones.
Easy System Expansion
If you want to add more solar panels to your system at some point in the future or simply want to start off with a small system, using microinverters makes this possible.
This is not the case with traditional string inverters that require a minimum-sized system as the inverter itself needs a certain amount of power to switch it on.
A solar array that uses microinverters provides maximum flexibility, allowing you to start off with a small one-panel system and expand over time as your roof grows or you’ve seen proof that it works.
Disadvantages of Microinverters
As you can see, there is a wide range of benefits to using microinverters but what about the potential disadvantages?
More Expensive
Let’s face it, we all saw this one coming. Creating a system that uses microinverters has greater upfront costs than a system that uses a traditional string inverter.
However, this does not mean it is a more expensive option in the medium to long term.
For instance, if you have to purchase string inverters twice during the life of your system (their average life is 10 years so this is common), then the cost comparison is very similar since a microinverter lasts around 25 years on average.
Also factor in the cost of the additional survey, scaffolding, materials and installation of replacement inverters, on which basis a microinverter is likely the cheaper option. We’ve not even factored in the costs after that house fire we mentioned earlier, but rumour has it those are rather expensive, too.
Moreover, in many cases, the fact that they have so many other benefits, such as being optimised for low light and capable of generating more power, makes them well worth the investment.
Greater Equipment Failure Rates?
There is a general attitude that the more components a system uses, the more theoretically there is more chance of failures to occur. That theory works in the game of Chinese whispers, so it might apply to your solar panels, too.
This is the name according to Wikipedia, but I feel it might be offensive now.
However, this really depends on the quality of the microinverter you choose.
For example, the Enphase microinverter reports a 1 in 2000 failure rate and they’re backed by a full replacement 25-year warranty.
In a 25-year life of a system, you’d need to budget at least two replacement string inverters (these carry a warranty of between 5-10 years) and would cost in the region of £1000-£2000 each time, plus any loss of generation as the whole system will be down.
Are Microinverters Right For You?
The advantages of microinverters make them ideal for almost any type of domestic solar installation, however, they are typically recommended for locations that are less ideal. That sounds deep, but it simply means that poor locations get more out of their microinverters.
For instance, if you live in a location that experiences a lot of shading or have a roof that isn't south-facing, microinverters will help you to maximise electricity generation even in low light conditions.
Microinverters FAQs
Installation and Maintenance
Note: Neither solar panels nor microinverters (or any inverters) can be installed DIY. They must be installed by an MCS-certified installer. On top of the risks of falling off your roof, there’s the high voltage to worry about.
Setting up a Microinverter-based Solar Array
In most cases, one or two string inverters are hooked up to an array of solar panels to provide DC to AC conversion for the entire system. It’s like visiting a group class at the gym.
However, when microinverters are used, the installation process is a bit more complex as there will often be one microinverter for every solar panel. Now, each solar panel has their own personal trainer.
That said, in some cases, there will be one microinverter for every two panels or even one for every four, although these two scenarios are rarer than a simple 1:1 ratio.
How many panels are fixed to every roof section will determine the number of microinverters required. The number of panels will also shape electrical connection requirements and the number of rails and brackets required.
Touching more on a subject already raised, the flexibility of a solar panel setup with microinverters can be greater if you have a suitable room for a ground-based installation. It also eliminates the chance of falling off your roof, although a professional setup is still required.
While in the case of string inverters, all solar panels ultimately connect to a single string inverter (most of the time), microinverters connect to each other, eventually transferring converted energy to the inside of the property for domestic use.
The exact steps required to install any given microinverter(s) or string inverter will vary depending on the manufacturer but in general, the above approaches are required.
How to Maintain a Microinverter
So, how can you maintain a microinverter? There are several ways of doing this.
For one, if you have a smart solar system you’ll want to monitor its performance throughout the year. By doing so, it will allow you to spot any sudden or gradual drops in performance.
Should either of these scenarios occur it may mean that your solar panels are suffering from a reduction in performance or it could be an issue with your microinverters.
Either way, if you suspect your solar panels/microinverters need to be repaired or replaced, hire an MCS-certified installer to take a look.
It’s also worth visually inspecting each solar panel and microinverter following a storm if it's safe to do so DIY.
This also applies if there has been high wind or/and hail stones. As a rule of thumb, if there’s a tree limb sticking out of your panels, there is a problem.
To perform a visual inspection, set up a ladder in a suitable and safe position and be sure to have a second person to hold it toward the bottom.
Only reach up to a safe point. Do not go out of your way to inspect your solar panels/microinverters if it compromises safety (e.g., trying to reach over the panel while on the ladder).
Always put safety first. If you can’t perform an inspection DIY, hire a professional.
However, if you can safely undertake a visual inspection DIY and spot any problems, you’ll want to hire an MCS-certified installer to perform the necessary repairs/replacement work.
Lastly, whether or not there’s been a storm or other harsh weather, it’s important to have your solar system (and therefore including your microinverters) inspected at least once a year by an MCS-certified installer.
We have also reviewed the best solar panels and covered how long solar panels last in the UK.
Next Steps For Your Solar Journey:
When planning to install solar panels for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:
To dive deeper into these topics, head over to our advice section, check out our YouTube channel for informative videos, or read a customer case study to see how others have benefited from their solar installation.
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