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Battery ready solar inverters in Australia

To understand solar battery storage you first have to get your head around the differences between 'AC Coupling' and 'DC Coupling'. It really makes a huge difference.

AC Coupling
Let's say you are in the market for solar and decided to buy the popular Fronius Primo or Symo inverter (or for that matter SMA SunnyBoy, Goodwe DNS, Growatt X etc).

If you looked at all the plugs and inputs on the underside of these inverters you would not see anything labelled 'Battery' because they aren't designed to connect a battery.


If you want a battery now or later you buy another inverter that handles the battery. This is what 'AC Coupling' means. The second inverter has absolutely nothing to do with your solar installation. Your Fronius, SMA, Sungrow, Goodwe etc inverter has already converted the DC panel power to AC to be used in your home or exported back out to the grid as surplus, but this is where the second inverter jumps into action, intercepting that surplus AC power and stores it in the battery.


Using a 'smart meter' which is clamped around your phase cables this let's the second inverter know whether to release or store battery power.


Some popular AC coupled inverters are:

SMA Sunny Boy Storage which connects to LG Chem, BYD and other high voltage batteries.

Tesla Powerwall 2 that has it's own in-built inverter and battery.

Sonnen that also has it's own in-built inverter and battery and is now officially 'Australian made'.
Goodwe SBP that works with a large variety of low voltage Lithium and Lead Acid batteries.


DC Coupling

DC Coupling a battery is very different to AC Coupling and provides some considerable advantages with very few drawbacks. However, the first step is to get a hybrid solar inverter; one that DOES have battery input connections on it's underside.


So instead of buying that Fronius Primo or Symo buy a Huawei, Growatt, Goodwe, Sungrow and now Q.Cells. All of the Huawei residential, single and three phase are hybrid models, but for the other brands you have to be careful to make sure you are getting the hybrid model. Fronius have a three phase variant of their Symo model called 'Symo Hybrid', Goodwe hybrids are the ES and EM single phase models and ET three phase, Growatt has a single phase SPH model, Sungrow the SH single phase model. There are others, but these are the main ones.


The battery plugs straight into the inverter. That's why it's called a hybrid. It manages both the solar panels AND the battery. The first obvious advantage to this is lower cost. One inverter not two. Secondly, the reporting software is all integrated under a single platform not two and the warranty is for one product not two.


If you don't like the battery choices available with the hybrid, then you always have the option to AC Couple as described above. With hybrids you get much more choice because you can DC Couple AND you can AC Couple.


However, the real killer advantage of hybrids is oversizing. With any 5kW inverter you are allowed to oversize it by 33.3% and be able to get the Government financial incentive (STCs), so that means 6.6kW of panels. However, if you have a hybrid inverter then when you are ready to connect the batteries you are also allowed to add more panels and claim the STCs on those extra panels. The logic behind this ruling by the Clean Energy Regulator is that the additional DC power from more panels can be directed straight into the battery and does not require conversion to AC. In most cases, factoring in other regulations about maximum voltage limits, it means you can install 7.5 to 8kW of panel power on a 5kW inverter.


The best hybrid inverters?

On many levels we think Huawei is the clear winner for both their single phase and three phase models, both of which are several hundred dollars cheaper than the non hybrid Fronius Primo and Fronius Symo and yet offer a better warranty (full ten years parts and labour). In fact, you could spend the approximately $300 price difference on extending your Huawei warranty to 15 years parts and labour. However, brands like Goodwe and Sungrow have advantages over Huawei, especially where backup emergency power is concerned.


The Fronius Symo hybrid is a really good hybrid inverter too, connecting to it's own, LG Chem and BYD batteries. It's only got a single MPPT so in many cases, all your panels will need to be facing the same way and you can't use optimisers on it unless ALL your panels are optimised (it's just because it uses parallel strings, but that's another story).


Goodwe made their reputation with their battery inverters and the single phase EM and ES models and ET three phase (5kW and 10kW) are excellent and get as close as any to a UPS emergency circuit with a few milliseconds break as it islands the inverter from the grid during a power failure.


Sungrow single phase SH5 hybrid has out for quite a long while now and has built up a solid reputation working with the Samsung Powercube battery.


The new Growatt SPH is very snazzy looking, reasonably priced and supports it's own Lithium battery. The battery is superb value for money (see below) but it only works with the Growatt inverter, or at least, that' s what we are told. They also have a very well priced AC Coupled inverter SPA 3kW which connects to their battery as well.


Is it cheaper to DC Couple than AC Couple?
Yes and No. If you have already got a solar installation then it's probably not going to make a huge difference, but if you haven't, then yes.


Here are some ideas on price.


AC Coupled pricing example.

If you were to purchase a Fronius Primo it would cost you $2,030 at time of writing.
Then you went out and bought an SMA Sunny Boy storage inverter for $3,235
and a 10kWh LG Chem battery for $7,980
Add on $1,500 for installation of the SMA Sunny Boy Storage and LG Chem

All up, you've spent $14,735


DC Coupled pricing example
You purchase a Huawei SUN2000L single phase hybrid for $1,600
and spend another $220 for the Huawei smart meter.
You then buy an LG Chem 10kWh battery (high voltage model) for $7,980
Delivery and installation of the LG Chem battery and connecting six wires to the
Huawei and a battery breaker between the two is about $800.

(We assume that the Huawei is already previously installed)

Total $10,600


As you can see, the price difference is because you bought and installed two inverters.

The best known 'AC Coupled' inverter and battery is Tesla Powerwall 2. The Powerwall inverter is inside the battery box. They cost $11,700, and add on about $2,000 for delivery and installation, making the total including Fronius Primo $15,730


How can you spot a hybrid solar inverter?

Easy. The one thing they all MUST have are battery inputs, as shown in the picture below of the Huawei hybrid.




If you have a battery, whether its plugged into the bottom of a hybrid or AC coupled you must have a smart meter. Not the smart meter you get from Synergy, it is a smart meter that works with the inverter.


Huawei Smart meter (single and three phase) and what they do below...



Batteries aren't connected yet to this Huawei hybrid's energy graph as you can see they are greyed out. That's normal as very few people are connecting batteries yet in WA.

Some examples of battery pricing for hybrid inverters.

Growatt's 6.5kWh battery is $3,795 making the cost per kWh of storage $584
Sungrow's Samsung cell 4.8kWh battery is $3,900, so $812 per kWh
BYD's 3.5kWh battery is $2,500, so $714 per kWh
LG's 10kWh battery is $6,595, or $695 per kWh

You can, of course parallel batteries together, so for example 2 x Growatt 6.5kWh = 13kWh at a cost of $7,590

There are other Lithium Ion batteries like Pylontech and ATL too, and many hybrids connect to lead acid batteries and can be used 'off-grid' although the manufacturers usually say they don't recommend it (mostly because of generators, but that's another story and not relevant to city 'on-grid' readers as most of you are).

The price is not right...yet

The value to you of a kWh of battery storage in Perth, in 2019 is 21.7 cents per day or $79 a year. That's worked out by taking the cost of a kWh of Synergy power at 28.83 cents and deducting the 7.135 cent feed in tariff you would have been paid for surplus solar if you weren't storing it in a battery instead.

It's ironic that WA has pretty much the best circumstances in Australia for battey storage.
The largest gap between the price of power and the price paid for exports which makes battery storage more attractive than a smaller gap.

We also have huge issues with high grid voltages mostly caused by solar users pumping surplus solar out into the grid during the peak 10am to 2pm window instead of into a battery.

As lithium prices fall, battery prices fall, electricity prices rise, there will come a point where the economics line up, but a battery subsidy instead of a feed in tariff makes a lot of sense.

If we take the Growatt new 6kW Lithium battery at $584 per kWh then $584/$79 = 7.39 years. Allowing for a steady increase in electricity prices that might well be more like 6 years to get your money back. We think the battery flood gates will open when the price is down low enough to give people their money back after 5 years and then enjoy 5 more years of profits until the warranty expires. (Not saying that the battery will die exactly on its tenth birthday, just that it most likely will not be as efficient after that).