The Solar inverter is generally the first part to fail in the solar system, this is why we believe the solar inverter is a crucial decision when it comes to installing solar on your roof.Â
If you are trying to work within a budget or you don’t want to pay a premium price for the entire system, we strongly recommend you pay more to get a good quality inverter.Â
Why is purchasing a good inverter so important? The solar inverter is the brains of the operating system, the engine room if you like. It works by carrying DC power from your solar panels and converting it into the AC power we use in our homes. Without the solar inverter the panels on your roof are useless.Â
If one of your solar panels fails, not a big deal and an easy fix – depending on the configuration most of your solar system can still work. But if your inverter fails, that’s kind of a big deal – there is a whole bunch of panels on your roof staring into the sun with no benefit.Â
This is our guide on how to choose a good quality inverter, the differences between inverters in Australia and which one is right for you.
There are 4 product options available in AustraliaÂ
A string inverter is the most common inverter in the world. It’s a centralised inverter with panels placed in series or a “string”. A string inverter is a simple installation and doesn’t come with a lot of parts, which means it’s not too expensive.Â
A string inverter is great for those with panels facing in directions of two or less, a site without any shade and a simple installation. In most cases a string inverter will be quoted by a solar retailer or installer.
A Hybrid Inverter is a string inverter with the capability of also charging a DC Coupled Battery.
Micro inverters are exactly how they sound, they are little tiny inverters which sit on the back of each individual solar panel. You cannot have 1 micro inverter, you must have the whole system set up with micro inverters.Â
Their main benefit is individual panel optimisation in which each panel works as an individual, which you don’t get with a string inverter. If where you are installing solar has many different roof aspects or if it suffers from shade, micro inverters are a great choice.
An added benefit of micro inverters is the individual panel monitoring, allowing you to monitor the performance and output of each individual solar panel, making it easy to pick up on a panel fault or something of that nature.Â
A downside of micro inverters is the cost. With more parts and more labour you will be paying a lot more to have micro inverters installed.
Much like micro inverters, an inverter with DC panel optimisers allow you to optimise each individual solar panel.
This solution is best for those who have many different roof aspects or suffer from shade.Â
Inverters with DC panel optimisers do the change from DC to AC power in one centralised location just like a string inverter, while Micro Inverters do this at the panel.Â
The most common type of Inverter with DC Panel Optimisers is made by SolarEdge, where the inverter and the optimisers are all made by SolarEdge.Â
Much like Micro inverters DC panel optimisers have individual panel monitoring and they come with the same downside, which is cost.Â
If you have shade or you have a complex installation which worries you or your solar installer or retailer – there is another option!
The best example of this option is TIGO. As an example, a site may have shade in the afternoon on some West facing panels from a neighbouring tree, this shade happens at about 3pm in Winter and doesn’t affect the panels too much in summer. You don’t want to spend huge amounts of money on a small problem and so you don’t want SolarEdge or Enphase Microinverters.
TIGO will allow you to install a string inverter of your choice and then add TIGO Optimisers on a select few panels.
At Teho we get the same question everyday:
“Is my solar inverter compatible with a battery”. The answer depends on which battery you are interested in installing. If you are intending to install a DC battery, you will need to find out which one you’d like to install and which hybrid inverter will work with that battery. However, we do not recommend installing DC Batteries.
If you are intending to install an AC coupled battery such as; Sonnen or Tesla – it doesn’t matter which inverter you have. An AC coupled battery in simple terms has the ability to connect to the AC wires in your home. We strongly recommend you purchase an AC coupled battery over a DC battery.
Do you have shade?Â
YES = Micro inverters or Panel OptimisersÂ
NO = Any inverter will workÂ
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Will the panels be installed on more than 2 aspects?
YES = Micro inverters or Panel OptimisersÂ
NO = Any inverter will workÂ
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Do you need individual panel monitoring?
YES = Micro inverters or Panel OptimisersÂ
NO = Any inverter will workÂ
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Are you intending on installing a DC Battery NOT an AC Coupled Battery?Â
YES = Choose compatible hybrid inverter
NO = Any inverter will workÂ
Choosing the best inverter size for your home is another important decision when it comes to installing solar. The most obvious thing to do is install an inverter with the same capacity as the solar array, while this is true, a common practice in the Australian solar industry is oversizing your solar array against your inverter.Â
Why would I oversize my solar array? Most networks across Australia have limitations when it comes to inverter capacity, it’s normally 5kW’s per phase. If you are a single phase property the maximum inverter capacity you can install with no limitations is a 5kW inverter.
If you want to install a larger inverter, that’s easy too, you add something called an export limiter – the only downside is the cost.Â
The STC scheme which is commonly referred to as the Australian Solar Rebate allows a solar inverter to be oversized by 133%. This is why you will see 6.6kW quotes with a 5kW inverter or a 13.2kW quote with a 10kW inverter.Â
The concern for most is that their inverter being smaller than their solar array will affect their overall generation, this is untrue. It’s very unlikely that the solar panels will produce their maximum capacity, it would need to be the perfect day. It can be very much the opposite because simply put solar inverters like to operate at higher ranges, this improves their efficiency.Â
In short, oversizing your solar array against your inverter is a good idea.
Some homes in Australia are single phase and some are three phase. The best way to tell if you are single phase or three phase is to pop open your meter box and have a look if you have one main switch or 3 main switches. Another way to to tell is how many wires are connected to your home from the street, one wire or three.
If you have a single phase home you can only have a single phase inverter installed. If you have a three phase home you can either install a single phase inverter or a three phase inverter.
It’s extremely common in Australia to have a single phase inverter on a three phase home. We know what you’re thinking……. What about all my three phase appliances? Don’t stress too much about it, you won’t be penalised for it.Â
The energy meter installed at the site will net off the difference between what you consumed and what you generated at all times when it comes to solar. For example, your solar system generated 5kWh’s on one of the phases. On that same phase you consume 1kWh while the other 2 phases consume 2 kWhs’ from the grid.
The energy meter will calculate the difference between the consumption and the generation of electricity from the solar and charge you accordingly – in this case the site owes nothing.Â
Financially it’s clear it won’t make a difference, the value in installing a three phase solar inverter on a three phase home is spreading the load of electricity being exported to the grid from your solar system across all three power lines not just one.
With the help of installers, partners and industry professionals Teho has put together a list of inverters we like to install on your home or premises using the following criteria:
