Beginners Guide to Solar Inverters

by Oct 8, 2021Inverter, Micro-Inverter, Solar

Beginners guide to solar inverter

The inverter is certainly one of, if not the most, critical components of the solar system.

To keep it nice & simple, the inverter converts the DC (Direct Current) power from the sun to the usable AC (Alternate Current) power that is used in all of our homes and businesses. A reliable inverter is absolutely essential, but choosing the right inverter for your home can be confusing.

There are three main types of inverters used in the Australian market:

  1. DC string inverters (brands such as SMA, Fronius, SunGrow, GrowWatt)
  2. Micro-inverters (brands such as Enphase)
  3. Power optimisers (brands such as Solar Edge)

String Inverters

Such as Fronius Primo/Symo & SMA Sunny Boy/Sunny TriPower

DC (Direct Current) string type inverters are the most common type of inverter installed in Australia. These inverters are usually located in a central location – commonly beside the switchboard or in the garage. In most domestic solar power systems, there is usually only one central inverter. DC inverters are best suited for panel arrays with no shade or orientation issues.

Advantages of DC String InvertersDisadvantages of DC String Inverters
Most efficient compared to micro inverters and
power optimisers as long as there is no shading or multiple orientation issues.
Warranty is usually lower than micro inverters and power optimisers (usually between 5-10 years compared to 20 or 25 years).
All technology is located in 1 location.Restricted to a maximum of 2 panel orientations or tilts.
Easy to access to maintain.If inverter fails the entire solar system stops producing power.
Proven technology with some quality inverters like SMA being used for 40 years.DC cabling is used in the ceiling space which has to be run through HD conduit increasing installation costs.

Micro-Inverters

Such as Enphase IQ 7A

Micro inverters are the latest technology to enter the inverter market. True micro-inverter systems have an individual inverter located under each solar panel which is usually on the roof. There have been over 2 million of this type of inverters installed around the world since about 2008. The micro-inverters have been installed in Australia since 2011 when they attained the necessary Clean Energy Council certification.

The remote monitoring capability of the micro inverter systems production is very comprehensive. Both the owner and the installer can monitor the output of each panel and the entire system in real time which is an invaluable tool. As with any new technology, it can expected that rapid and ongoing advances and product improvements will take place in the micro inverter field. Two of the changes that are already in the pipeline are micro inverters are being integrated into the solar panels as they are produced, and two micro inverters are being integrated into one to control two panels instead of one. The micro-inverters are suitable for panel arrays that have shade issues or homes that have many small roof spaces which might be facing different directions. Click here to read our blog that goes into more detail about micro-inverters. 

Advantages of Micro-invertersDisadvantages of Micro-inverters
Suitable for roofs that have shade issues, any shading on the array will only affect the particular panel that is being shaded.Multiple inverters are more expensive to purchase which increases system costs.
Suitable for installations that have multiple orientations and/or tilts.If an inverter does fail, access to inverter is more difficult than with DC inverters.
Current inverters on the market have a warranty of between 15 and 25 years which is considerably longer than the DC inverters.
No DC cabling in the ceiling space reducing fire and safety issues and reducing installation costs.
If one inverter fails the rest of the system will operate.
Remote monitoring software allows the output of every inverter to be separately monitored. This makes troubleshooting and maintenance much
easier.

Power Optimisers

Such as SolarEdge P401

Power optimisers consist of a unit (optimiser) mounted under each panel similar to a micro inverter, plus a large central inverter which is located in a similar place to where DC string inverter would be located. These systems are most suited to larger type systems that have shade or multiple orientations. 

Advantages of Power OptimisersDisadvantages of Power Optimisers
Suitable for roofs that have shade issues, any shading on the array will only affect the particular panel that is being shaded.Multiple inverters are more expensive to purchase increasing system costs.
Suitable for installations that have multiple orientations and/or tilts.DC cabling is used in the ceiling space which has to be run through HD conduit increasing installation costs.
Current inverters on the market have a warranty of between 15 and 25 years which is considerably longer than the DC inverters.Still uses a central inverter, so if that inverter fails the whole system will stop producing (like with DC inverter systems).
Have a higher efficiency than micro inverters.If an optimiser fails - access to optimiser is more difficult than with DC inverters.
Remote monitoring software allows the output of every inverter to be separately monitored. This makes troubleshooting and maintenance much easier.

Questions to Ask Your Installer

Installing a reliable, quality inverter is vital to ensure the longevity and performance of your solar system. It’s really important to realise that a long-lasting, reliable system is the product of BOTH the panels and the inverter. In my opinion, there’s no point in spending big on quality solar panels if you don’t have a dependable inverter to match. It’s like putting a lawnmower motor in a Lamborghini body… The type and brand of the inverter is not something that you want to gloss over. Some of the questions that you should ask your installer/think about include:

  • Where the inverter is made?
  • How long has that company been in existence?
  • How long has that company been producing inverters?
  • What warranty is provided with the inverter and can it be extended?
  • Does the manufacturer have a reliable service network in Australia and/or allow the installer to carry out minor repairs?
  • Is there an Australian office and how many people are in that office? Is it just a token office with a salesperson?
  • Can you remotely monitor the solar production or does it cost any extra to have that capability?

What We Tell Our Customers

If your roof is ideal or close to ideal for solar, it is debatable whether paying a premium price for micro-inverters or power optimisers is worth it. If your panels have little to no shading, are not on multiple tilts and do not face multiple different directions, a string inverter system is a cost-effective, proven solution. Micro-inverters and power optimisers definitely have their place and can be an effective solution for more complex installations. At the end of the day, it comes down to your personal preferences, what your budget is and where your solar panels are going to be installed. 

I would highly recommend discussing with an accredited solar installer/designer (NOT a salesman) about the inverter and get them to explain why they have suggested that specific inverter for you – if they can’t justify why and back it up, that’s a red flag…

Nigel Phillips
Nigel Phillips

Director/Technical Manager at Electrical Sensations

Nigel has decades of experience in domestic, commercial and industrial electrical work, as well as 13 years of experience in the Solar Industry. As a Clean Energy Council (CEC) accredited solar designer and installer for both grid and off-grid solar power and battery systems, Nigel has the knowledge and expertise to create solutions to suit every client. Nigel is also one of the 23 solar experts in CEC’s Installer Reference Group, which assist the CEC in improving and shaping the small-scale PV and battery industry. Troubleshooting and fault finding are some of Nigel’s strengths.

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