The role of the solar inverter in your solar PV system

Here’s our guide to understanding how a solar inverter works, the types of solar inverters which could form part of your rooftop solar power system and how to choose a solar inverter.

 

What is an inverter?

Think of your solar inverter as the brains of your solar power system. A solar inverter takes the direct current electricity (DC electricity) generated by your solar PV system and converts it to alternating current electricity (AC electricity). This electricity is then available to use in your household or business electricity circuits. 

While your solar panels are mounted on the roof for maximum sun exposure, a solar inverter is a box which is usually mounted on a wall outside your home or in a garage or laundry. This is to protect your solar inverter from the weather and keep it close to your power board. 

With the most complex role in your solar PV system, the solar inverter is the most sophisticated component and, unfortunately, can be the component most likely to fail first. To maximise the performance and lifespan, solar inverters should always be in the shade where possible.

 

How a solar inverter works

As you may know, generating solar power starts with the sun shining on your solar panels. Here’s what happens next:

  1. The energy from the sun’s rays are captured by the photovoltaic (PV) cells in your solar panels. This makes electrons inside your solar panel cells move, creating energy.
  2. Circuits within the cells collect this energy and convert it into direct current or DC electricity.
  3. A solar inverter takes the DC electricity and transforms it into alternating current or AC electricity.
  4. This AC electricity  can then be used to run the appliances, equipment, lighting and other electrical items in your home or business.

If your solar power system generates more electricity than your home requires, excess solar power is then either sent to a battery storage system or back into the power grid, depending on your solar PV system set-up.

 

Types of solar inverters

There are four main types of solar inverters your home or business solar PV system is likely to have. Each one has different features and benefits:

String inverters 

String inverters are the most common solar inverter type for homes. Usually, there’s one string inverter for each solar installation.

They are called 'string inverters' because a string of solar panels is connected to one inverter. The inverter is mounted on an external wall, usually near the main power switchboard. This has been a common solar PV system design for decades and works well for most solar installations.

If you’ve heard the saying ‘A team is only as strong as your weakest link’, this applies to string inverters too. If one panel is shaded, dusty or dirty, or fails for any reason, the generation output of the whole string could be diminished, usually to the level of the lowest producing panel.

In other words, if one panel drops to 50% output for some reason, the whole string of panels drops to 50% output. To help avoid this happening, it’s important to keep an eye on any shading issues on your rooftop, keep your solar power system well maintained   and pay attention to the system's performance using your solar monitoring data so you can try to detect any problems early.

Microinverters 

Instead of having one solar inverter for your whole solar power system, each solar panel can have its own microinverter. 

A microinverter installation can cost more but could give you the most output from your individual solar panels. Each one of these solar inverters gets attached directly to one solar panel on the roof. Unlike with string inverters, if a single solar panel fails or becomes shaded, you would only lose or experience reduced output from that one panel, rather than your whole solar panel array.

You might find a microinverter is worth considering if you have shading issues which come and go through the day, you are considering adding more solar panels at a later date or if you have a really large roof.

A downside of microinverters is that because they are located with the solar panels on your roof, they are generally more exposed to weather than a string inverter. If one fails, you would need to book a solar installation professional to get up on your roof to resolve the issue.

Battery inverters  

A battery inverter is generally the best option if you want to install a battery and you have an  existing solar PV system, or are wanting to keep your battery separate from your solar panels and run through a different inverter.

A battery inverter will send the solar power to your battery and then later turn the power stored in your battery into AC electricity to use in your business or household circuits.

Hybrid inverters  

Hybrid inverters, which can also be known as 'multi-mode inverters', aren’t that common in Australia but can be used to connect batteries to your solar PV system. 

A hybrid inverter engages with the connected batteries through a process known as 'DC coupling'. This is when both the solar panels and batteries use one inverter and the DC electricity from the solar panels charges the batteries through a DC charger. The electronics in a hybrid inverter take care of the charging and discharging of the battery. 

You can get a hybrid inverter without a battery if you’re planning to get a battery in the future but only certain models will work with certain batteries. Do your research carefully so you don’t get stuck with a hybrid solar inverter which won’t be compatible with the type of battery you want to install later.

 

What types of solar inverters suit your needs?

Your solar installer or retailer will be able to recommend the best type of solar inverter to suit your requirements and solar PV system design. Just as it’s important to know the risks of choosing cheap solar panels, it’s important to look into the quality of the solar inverter you choose.

Top tip: If you want to add a battery in the future but you don’t think it will be any time soon, you might consider a string inverter or microinverters for now. You can always deal with the battery installation if and when it happens. You’ll then have the option to replace your inverter at that time, choose an extra battery inverter or an "all-in-one" battery with its own built-in inverter. By the time you install a battery, your options may have increased as the technology develops.

 

Get the right solar inverter size for your solar PV system

Your solar company should help you work out what size solar PV system you need to suit your needs – and this includes what size solar inverter you’ll need.

Overall, your solar inverter size will depend on the size of your solar panel array. Each inverter is sized in kilowatts (kW) as the maximum amount of AC electricity and DC electricity that the inverter can manage. Here are some tips to help you work out what inverter size is appropriate:

  • Your inverter doesn’t need to be the same kW size as your solar panels. A solar panel array will rarely generate at its full rated maximum because of a range of factors such as the amount of sunlight, the age of the panels, weather conditions and so on. 
  • The output capacity of your solar inverter must be at least 75% of your solar panel array capacity. Solar PV systems must comply with this requirement to qualify for STCs (Small-scale Technology Certificates, the financial incentive scheme or "rebate" that is often offered as a discount on the purchase price of a solar PV systems).
  • If you choose the maximum number of solar panels for your solar inverter size, it could be hard to add more solar panels in future unless you upgrade your solar PV system.

You should also discuss any other limitations with your solar installation company, such as the components of the system, any limits on solar export to the power grid and other factors relevant to your situation and location. 

 

How to choose a solar inverter

We’ve put together some common questions to ask your solar installation company when you’re exploring different types of solar inverters. 

Is the solar inverter CEC approved?

Being Clean Energy Council (CEC) approved means the solar inverter is meets the relevant Australian Standards. Beyond being CEC approved, check the company that manufactures the inverter, including its history and how long it has been in business. 

Is the solar inverter weatherproof?

The more protected your solar inverter is from the weather, the longer it is likely to last and the better it is likely to perform. Check out the specifications of the solar inverters you are interested in and speak to the solar installation company to find out where they plan to install the inverter. If your inverter is going to be installed outside, check whether they recommend a weather-proof cage.

What’s the solar inverter warranty?

Most grid-connected inverters usually last around 10 to 20 years.
Depending on the solar inverter manufacturer, warranties for inverters are usually between 5 to 12 years, and some can include the option to extend the warranty if you pay an additional cost. Take a look at the solar inverter you would like and its features, and consider what warranties are offered. 

Can I expand my solar inverter?

If you think you’ll add to your solar power system in future, this is worth thinking about now. Speak to your solar expert on what you’re planning now and into the future to find the solution they recommend based on your needs.

Does the solar inverter come with solar monitoring functions?

To make the most of your investment in solar, it helps to keep an eye on your solar data. Solar monitoring will record your solar PV system's performance so you can check how your system performs across the day and across seasons, track how much you’re exporting to the power grid and more.

Many solar inverters offer sophisticated in-built monitoring options, however if your solar inverter doesn't come with smart monitoring, you could consider paying for a third-party monitoring system. Some of these systems may involve ongoing fees for the service, but could provide valuable information to help you make the most of your solar power.


Now that you have more information about solar inverters, you might like to learn more about solar PV systems. Get all the facts about solar PV systems and tips for shopping for solar for your home or business in our comprehensive guide. 

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