Solar Batteries
Updated March 2025
There is a battery rebate coming soon to Western Australia.
The latest announcement contains a little more information.
The main takeaways are:
You can register your interest.
The rebate is $500 per kWh of battery storage.
The battery storage capacity must be at least 5kWh
19,000 Synergy customers will be eligible with roll out over several 'rounds'
The scheme will be administered by a 3rd party provider.
Interest free loans up to $10,000 will be available for low and middle income earners.
The scheme will commence on, or before July 1st 2025.
The rebate includes new, additional and replacement battery systems.
Batteries must be Virtual Power Plant (VPP) capable and WIFI connected.
Retailers must publish battery prices ahead of each round of rebates.
Why the rebate favours 10kWh batteries not smaller or larger ones.
A typical battery and inverter combo with a 5kWh battery costs $6,500.
The rebate on that battery at $500 per kWh will be $2,500.
That means $4,000 out of pocket cost to the homeowner.
A 10kWh battery and inverter combo costs $10,000
The rebate though is double at $5,000, so out of pocket cost, $5,000
So for $1,000 more you get 5kWh more battery storage.
A 5kWh battery is proportionately more expensive than a 10kWh battery. (e.g. $6,500 versus $10,000)
That's because the starter 5kWh battery needs a power control unit, BMS and current flow meter installed.
Adding an extra 5kWh battery onto the 5kWh 'starter kit' is quick and easy and proportionately cheaper.
Are all 10kWh batteries $10,000?
The average price is closer to $12,000, but there are certainly plenty of lower cost brands at $10,000.
SAJ, Growatt, Alpha to name a few of them.
People with hybrid inverters and meters are usually able to simply add batteries.
Their cost, even for a top quality battery, might be $10,000 because some of the other 'stuff' is already installed.
I'm often asked what battery is best.
Cheapest, best build quality, most safety features, best support, best management system, best support or warranty?
I'd say, overall, Sigenergy and iStore have the best batteries with cheaper brand Growatt not too far behind with their new APX battery.
These batteries with their optimisers and parallel connection just make for a smoother long term journey.
The fire extinguishing features of Sigenergy and iStore may never be needed but they are a comfort.
Are Sungrow, Goodwe, Alpha and BYD also good batteries?
Yes. They are no frills connected batteries, but still good quality.
Some battery brands we supply and install include...
Sigenergy
iStore
Sungrow
Goodwe
Alpha ESS
Growatt
Backup power during a grid outage
Most people think that when they get a battery they also get 'backup' power during grid outages.
That is most certainly NOT the case.
Most inverters have an additional 'backup box' that is usually installed by the switchboard.
In addition to the cost of that box, the installing electrician has to almost re-wire the whole switchboard.
Very time consuming job adding backup and therefore, usually quite expensive.
Some inverters have the backup circuits in-built and don't need a separate box...
...even then there's still a lot of install time, and quite often more expensive higher current carrying cables than usual.
It varies from product to product but allow $2,000 as an average to add 'backup' with your new battery.
Feed in tariff, REBS and DEBs
The Western Power and Synergy rules say that if you add to or change your solar then you move from REBs to DEBs.
That means going from a 7 cent per kWh feed in tariff, to 2 cents per kWh up to 3pm and 10 cents after 3pm .
However, the key word in the rule is 'solar'.
If you AC Couple a battery you aren't touching the solar at all, so you keep your REBs.
AC Coupling or DC Coupling a battery.
DC Coupling means that the battery plugs directly into the hybrid solar inverter.
Almost all solar inverters installed before 2018 cannot plug in a battery because they aren't hybrids.
Probably 80% of those installed since 2018 can't either because solar inverters are cheaper than hybrids.
We can tell you easily enough what you've got, just email us the model number from the label.
If you haven't got a 'hybrid' inverter then one option is to replace your inverter with a hybrid.
Alternatively you can AC Couple a battery.
An AC Coupled battery has no connection at all to your existing solar, it's standalone.
Inside the AC battery is an inverter and a battery charger.
Extra solar panels with a battery?
Most hybrid inverter manufacturers allow 200% oversizing when a battery is connected to the inverter.
For example, a 5kW inverter might have 10kW of panels connected, or a 10kW inverter, 20kW of panels.
Without a battery oversizing is limited to 133%.
It isn't always an easy matter to add extra panels to an existing solar installation.
When we started in business in 2011, 190W panels were the popular size.
Three years later, 250W was normal, and by 2020 we were installing 330W panels.
Today's panels are 440W, 475W, sometimes 500W.
The efficiency of panels has increased from 15% in 2011 to 23% today.
Panels have also become considerably larger.
Modern panels have different voltage and current outputs to older panels.
Finding new panels that have similar electrical properties to the older ones is very difficult.
We look at the possibility of adding panels on a case by case basis but quite often the solution is a whole new system.
Take down the old panels and inverter, send them to Africa for a second life and install a new system.
The Government subsidy (STCs) is still available to you if you replace the entire system, plus this new battery subsidy.
Export limiting can make things very difficult.
The rule in WA has been, for a very long time that you get paid no feed in tariff if your solar inverter(s) are over 5kW.
A new rule introduced in 2022 that applies to any changes to your solar is a 1.5kW export limit.
Let's say you have a 5kW three phase Fronius Symo inverter installed in 2017.
You now like the look of Sigenergy's new inverter and battery and want to add their 5kW 3 phase model, AC Coupled with a battery
Western Power say that the Sigenergy inverter is a hybrid inverter and therefore 'solar'.
You protest (in vain) that you aren't adding any panels to the Sigenergy inverter.
The fact that it CAN connect panels even if none are actually connected makes all the difference.
Now you have a 5kW Fronius and a 5kW Sigenergy making 10kW and that means no feed in tariff and 1.5 export limit.
That means the Fronius and Sigenergy have to communicate with each other to limit exports to 1.5kW.
They don't...not even if the Fronius is connected to the Sigenergy 'smart port' as some have suggested to me.
You have to export limit the Fronius to 1.5kW and that requires a $700 or so Fronius power meter.
It's about at this point when people realise that it's simpler and probably cheaper to replace the Fronius with the Sig.
iStore/Huawei 10kWh battery
Fronius GEN24+ inverter & 16.5kWh BYD battery
This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.
Updated March 2025
There is a battery rebate coming soon to Western Australia.
The latest announcement contains a little more information.
The main takeaways are:
You can register your interest.
The rebate is $500 per kWh of battery storage.
The battery storage capacity must be at least 5kWh
19,000 Synergy customers will be eligible with roll out over several 'rounds'
The scheme will be administered by a 3rd party provider.
Interest free loans up to $10,000 will be available for low and middle income earners.
The scheme will commence on, or before July 1st 2025.
The rebate includes new, additional and replacement battery systems.
Batteries must be Virtual Power Plant (VPP) capable and WIFI connected.
Retailers must publish battery prices ahead of each round of rebates.
Why the rebate favours 10kWh batteries not smaller or larger ones.
A typical battery and inverter combo with a 5kWh battery costs $6,500.
The rebate on that battery at $500 per kWh will be $2,500.
That means $4,000 out of pocket cost to the homeowner.
A 10kWh battery and inverter combo costs $10,000
The rebate though is double at $5,000, so out of pocket cost, $5,000
So for $1,000 more you get 5kWh more battery storage.
A 5kWh battery is proportionately more expensive than a 10kWh battery. (e.g. $6,500 versus $10,000)
That's because the starter 5kWh battery needs a power control unit, BMS and current flow meter installed.
Adding an extra 5kWh battery onto the 5kWh 'starter kit' is quick and easy and proportionately cheaper.
Are all 10kWh batteries $10,000?
The average price is closer to $12,000, but there are certainly plenty of lower cost brands at $10,000.
SAJ, Growatt, Alpha to name a few of them.
People with hybrid inverters and meters are usually able to simply add batteries.
Their cost, even for a top quality battery, might be $10,000 because some of the other 'stuff' is already installed.
I'm often asked what battery is best.
Cheapest, best build quality, most safety features, best support, best management system, best support or warranty?
I'd say, overall, Sigenergy and iStore have the best batteries with cheaper brand Growatt not too far behind with their new APX battery.
These batteries with their optimisers and parallel connection just make for a smoother long term journey.
The fire extinguishing features of Sigenergy and iStore may never be needed but they are a comfort.
Are Sungrow, Goodwe, Alpha and BYD also good batteries?
Yes. They are no frills connected batteries, but still good quality.
Some battery brands we supply and install include...
Sigenergy
iStore
Sungrow
Goodwe
Alpha ESS
Growatt
Backup power during a grid outage
Most people think that when they get a battery they also get 'backup' power during grid outages.
That is most certainly NOT the case.
Most inverters have an additional 'backup box' that is usually installed by the switchboard.
In addition to the cost of that box, the installing electrician has to almost re-wire the whole switchboard.
Very time consuming job adding backup and therefore, usually quite expensive.
Some inverters have the backup circuits in-built and don't need a separate box...
...even then there's still a lot of install time, and quite often more expensive higher current carrying cables than usual.
It varies from product to product but allow $2,000 as an average to add 'backup' with your new battery.
Feed in tariff, REBS and DEBs
The Western Power and Synergy rules say that if you add to or change your solar then you move from REBs to DEBs.
That means going from a 7 cent per kWh feed in tariff, to 2 cents per kWh up to 3pm and 10 cents after 3pm .
However, the key word in the rule is 'solar'.
If you AC Couple a battery you aren't touching the solar at all, so you keep your REBs.
AC Coupling or DC Coupling a battery.
DC Coupling means that the battery plugs directly into the hybrid solar inverter.
Almost all solar inverters installed before 2018 cannot plug in a battery because they aren't hybrids.
Probably 80% of those installed since 2018 can't either because solar inverters are cheaper than hybrids.
We can tell you easily enough what you've got, just email us the model number from the label.
If you haven't got a 'hybrid' inverter then one option is to replace your inverter with a hybrid.
Alternatively you can AC Couple a battery.
An AC Coupled battery has no connection at all to your existing solar, it's standalone.
Inside the AC battery is an inverter and a battery charger.
Extra solar panels with a battery?
Most hybrid inverter manufacturers allow 200% oversizing when a battery is connected to the inverter.
For example, a 5kW inverter might have 10kW of panels connected, or a 10kW inverter, 20kW of panels.
Without a battery oversizing is limited to 133%.
It isn't always an easy matter to add extra panels to an existing solar installation.
When we started in business in 2011, 190W panels were the popular size.
Three years later, 250W was normal, and by 2020 we were installing 330W panels.
Today's panels are 440W, 475W, sometimes 500W.
The efficiency of panels has increased from 15% in 2011 to 23% today.
Panels have also become considerably larger.
Modern panels have different voltage and current outputs to older panels.
Finding new panels that have similar electrical properties to the older ones is very difficult.
We look at the possibility of adding panels on a case by case basis but quite often the solution is a whole new system.
Take down the old panels and inverter, send them to Africa for a second life and install a new system.
The Government subsidy (STCs) is still available to you if you replace the entire system, plus this new battery subsidy.
Export limiting can make things very difficult.
The rule in WA has been, for a very long time that you get paid no feed in tariff if your solar inverter(s) are over 5kW.
A new rule introduced in 2022 that applies to any changes to your solar is a 1.5kW export limit.
Let's say you have a 5kW three phase Fronius Symo inverter installed in 2017.
You now like the look of Sigenergy's new inverter and battery and want to add their 5kW 3 phase model, AC Coupled with a battery
Western Power say that the Sigenergy inverter is a hybrid inverter and therefore 'solar'.
You protest (in vain) that you aren't adding any panels to the Sigenergy inverter.
The fact that it CAN connect panels even if none are actually connected makes all the difference.
Now you have a 5kW Fronius and a 5kW Sigenergy making 10kW and that means no feed in tariff and 1.5 export limit.
That means the Fronius and Sigenergy have to communicate with each other to limit exports to 1.5kW.
They don't...not even if the Fronius is connected to the Sigenergy 'smart port' as some have suggested to me.
You have to export limit the Fronius to 1.5kW and that requires a $700 or so Fronius power meter.
It's about at this point when people realise that it's simpler and probably cheaper to replace the Fronius with the Sig.
This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.