A guide to solar inverters: what are they and how do they work?

By harnessing light from the sun, solar power allows us to collect and convert enough energy to power homes, offices, appliances, heating systems and even transportation – all with minimal impact on the world around us.

We tend to think of solar panels as the sole generator of this power. And while they do play a big part in absorbing and storing energy, they’re just one component in the overall process. Today, we’re going to look at an overlooked aspect of this form of energy – solar inverters.

Without this all-important component of solar power, we wouldn’t be able to utilise sunlight as efficiently and effectively. Read on to find out more about solar inverters, including what they are, how they work, different types available, choosing the right one, and how to make sure your inverter continues to operate to a high standard.

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What are solar inverters?

In essence, solar inverters are the bridge between raw sunlight and the energy that powers your home. They take the direct current (DC) which solar panels absorb, then convert that into an alternate current (AC), which provides power for your home.

In doing this, they not only streamline the supply of energy to your home, but also heighten safety levels. If DC were to be used to power a household, most gadgets and appliances would be unable to handle the electrical surge. Solar inverters negate this danger, while also optimising the production of electricity itself so that very little goes to waste.

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How do solar inverters work?

As we’ve touched on, at their core a solar inverter works by taking stored DC energy and converting it into AC. This is a four-step process, which happens almost instantaneously in order to keep a building or appliance supplied with power.

A standard four-step DC-to-AC converter will work as follows:

1. The inverter receives DC and channels it through its internal transformer
2. The transformer lowers the voltage, converting the DC to AC
3. The DC runs through two or more transistors
4. The transistors get rapidly turned on and off to feed the two sides of the transformer

Once the process is complete, your home will have enough electricity to draw on to be able to efficiently power it.

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Different types of solar inverters

There are four primary types of solar inverters. As you might expect, they all have merits and detractors, depending on exactly what you need out of your unit. Here are the different types you can choose between, as well as a breakdown of each.

Standard String Inverters

Arguably the most common type of inverters, these units collect DC energy from a variety of solar panels, centralising the current and converting it all at once. String inverters will often be mounted on the side of the home, garage, or near the power metre.

Pros of standard string inverters:

• As the most common option on the market, they’re often also the cheapest
• Installation is quicker and less expensive owing to there being fewer parts
• Simpler to diagnose problems with them
• Easier to maintain owing to their placement away from the roof

Cons of standard string inverters:

• Limited power supply if a home receives a lot of shade, or limited hours of sunlight
• A single panel dropping in production can reduce the impact of the entire solar array

Optimised String Inverters

This works in a similar way to a standard inverter, but with individual optimisers attached to every solar panel. This serves to produce a more consistent flow of energy – with the optimiser only allowing DC to be converted to AC once a panel has absorbed the exact right amount of sunlight.

Pros of optimised string inverters:

• A consistent flow of energy to the converter, with one panel having far less of an impact on the array
• Optimised power options, even during periods of shade or low light
• Warranties tend to be longer for these types of solar inverters
• Data monitoring on an individual panel level is easier

Cons of optimised string inverters:

• Price for parts and cost of labour tends to be a bit higher
• Some optimisers will be attached to a panel at the factory. That means if they break they might not be repairable

Micro Inverters

In this instance, each individual panel contains a tiny inverter, which will activate and convert DC to AC once that panel gets the right amount of light. This localised inverter makes it easier to spot which panels are or aren’t performing efficiently.

Pros of micro inverters:

• Energy is optimised at a panel level
• They’re well-suited for complex roof systems, even when shading is natural
• It’s easier to monitor data on a panel-by-panel basis
• Production is kept at a maximum at all times, even when shaded
• One poorly performing panel will not negatively impact the entire array

Cons of micro inverters:

• More expensive to buy and run than most other converter types
• Harder to reach when repair is required, as they’re often installed on the roof

Hybrid Inverter Systems

Hybrid inverters don’t just rely on solar power, they also take any surplus DC generated and send it to a solar battery which is attached to the system as a backup. On days when the panels themselves receive less light, the inverter can dip into the battery and convert the stored DC into AC.

Pros of hybrid inverter systems:

• Intelligent software draws from the grid when electricity is cheapest, saving you money in the long run
• You can choose to run hybrid inverters with or without the backup battery system if you so wish
• It’s possible to add a battery to the system later down the line if you aren’t happy with the solar array alone

Cons of hybrid inverter systems:

• Because they’re not a dedicated type of inverter, energy production is sometimes less optimised

What’s more, aside from a traditional hybrid unit, you’ll also be able to choose between an inverter that is or isn’t connected to the electrical grid of your city. These inverters are given the names on-grid or off-grid, depending on how they work. Both of these types of inverters have their pros and cons. It’s important to know the difference:

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How to choose the right kind of solar inverter for you

With so much variety, it might be tough to know which type of solar inverter is going to work best for your needs. As such, the most important part of selecting one is to fully understand what it is you’re looking for. Take a step back and assess all of the following criteria:

• Look at the core parameters. Each inverter will operate using a series of parameters to store and convert DC into AC. You’ll want to work out the input DC voltage, output AC voltage, frequency, and circuitry of each inverter to see if they will safely and effectively operate in your home. You’ll also need to decide if you want to stay connected to the electrical grid in some way, or become totally independent.
  
• Assess how much sunlight your house regularly receives. As we’ve discussed, some inverters and solar arrays will be more efficient, depending on the amount of sunlight your home gets. If you have shaded areas, it might be wise to invest in inverters which optimise your output on a panel-by-panel basis.
  
• Decide if you need optional accessories. If you want to stay on top of the efficiency and effectiveness of your inverter, you might want to think about including add-ons like a monitoring device. This helps you stay on top of energy production, as well as highlighting any faults in your solar array.
  
• Read up on safety ratings and reviews. Before committing to any company, make sure to do your research. In the modern world, it’s quite easy to find online reviews from past customers. While these should always be taken with a pinch of salt, the overall score is a good yardstick for the reliability of suppliers.

If you don’t want to do the work yourself, you can always turn to one of our tried and trusted partners. We only work with names we know we can rely on, such as:

• Fronius
• SolarEdge
• SMA
• Enphase
• Huawei

Once you know exactly what you’re after, it’s time to directly compare your solar inverter options. While specific brands may vary, this is a good way to understand what different types of inverters offer:

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Maintenance tips to sustain your solar inverter

While some solar inverters come with an in-built monitoring system, there are still steps you can take to ensure your unit stays in the best condition possible. Follow this advice to effectively maintain your inverter:

• Think about the installation environment. For inverters which are standalone, finding the perfect spot to install an inverter is crucial in ensuring it has a long lifespan. Try to keep it away from places where it’s likely to become damp, or overheat. A cool room with plenty of installation is your best bet.
  
• Regularly check the battery. Not all inverters will come with a battery attached, but if you’re using a hybrid version it’s important to regularly assess its health. Try to ensure it’s well ventilated, and avoid wearing jewellery or metallic items when touching or going near it.
  
• Avoid input over-voltage. This is really something to consider in the early stages of choosing an inverter. It’s crucial you choose one which will be able to handle the voltage requirements of a building. Failure to do so can cause damage, as well as more serious things like electrical fires.
  
• Replace necessary parts. When one piece of your car stops working, you don’t scrap the whole vehicle. The same is true with solar inverters. Find what’s broken, and make sure to replace it via the same supplier who installed your solar array in the first place. That’s the only way to ensure it will continue to work as efficiently as possible.
  
• Have a professional install it if you’re unconfident. While installation is possible on your own, this should be avoided if you’re remotely unsure of what to do. Always rely on a trained professional.
  

Do you feel like you have a better understanding of what a solar inverter is and how it works? At Otovo, we work with manufacturers whose inverters stand out for their efficiency and safety. We trust all of the following names to produce elite quality units, which optimise solar energy efficiency:

• Fronius
• Ginlong Solis
• Growatt
• Huawei
• SMA
• Solar Edge

Make sure to get in touch with the Otovo team if you have any further questions, or want to discuss installing an inverter (or general solar array) on your property.