How the iStore battery works
The iStore S1 is a stackable DC-coupled battery. Each stack takes one, two or three Energy Storage Modules: the 7000, 14000 or 21000 units, giving 6.9, 13.8 or 20.7 kWh of usable capacity. A maximum of three modules can be installed per stack, and the compatible hybrid inverter sets how many stacks you can connect in parallel: up to four stacks for 82.8 kWh per inverter.
The battery doesn’t invert power on its own. It pairs with an iStore hybrid inverter (single or three-phase, 5 to 25 kW across the range) that handles the solar, the battery and your home loads. During a grid outage, with the right backup equipment, it can support selected circuits you’ve nominated. You monitor charge level, solar and household use from the iStore monitoring app.
More on the iStore range we install and how our Battery Storage service works.
Which iStore battery size suits your home
Start with what your home draws between sunset and sunrise, because that’s the gap the battery is filling. Your Synergy bill or app will show it. Add a margin for cloudy days and anything you plan to add (EV, pool pump, reverse-cycle running overnight).
- IS-BATT-7000-S1 (6.9 kWh usable): suits smaller households that mainly want to soak up daytime solar they’d otherwise export. Rated charge and discharge is 3.5 kW.
- For example, a home using around 10 kWh overnight would get through with headroom, with 7 kW of charge/discharge power.
- IS-BATT-21000-S1 (20.7 kWh usable): for larger homes or households with an EV or ducted air-con running after dark, with 10.5 kW of charge/discharge power.
First, the inverter: if you want to add a second or third stack later, don’t start on the single-phase 5000 or 6000, which support one stack only; a larger single-phase or three-phase inverter leaves room to grow. Second, backup: the backup equipment and the circuits you wire for it set how much your home can run in an outage, not the battery capacity alone. For the WA rebate, the amount scales with usable capacity up to 10 kWh, so any stack of 10 kWh usable or more (including a 13.8 kWh IS-BATT-14000-S1) receives the maximum.
iStore S1 battery at a glance
iStore S1 battery sizes
IS-BATT-7000-S1
IS-BATT-14000-S1
IS-BATT-21000-S1
Scale up later
Rebates on an iStore battery in Perth
The iStore S1 range sits in the eligible band for both the federal discount and the WA scheme. The exact figures depend on size and install date.
- Federal discount: applied up front through STCs. From 1 May 2026 the factor is tiered: 100% on the first 14 kWh of usable capacity, 60% from 14 to 28 kWh, and 15% from 28 to 50 kWh. The rate steps down every six months and the program ends on 31 Dec 2030. Your install date, not your contract date, sets the rate.
- WA Residential Battery Scheme: for Synergy customers, the rebate scales between 5 and 10 kWh usable, up to $1,300 at 10 kWh; any battery above 10 kWh receives the maximum. You must commit to a VPP product with Synergy or Horizon Power.
- Synergy Supported Solutions List: the IS-HYB-1PH and IS-HYB-3PH series are listed with a DER-Storage client, which is the entry the WA scheme relies on. We confirm your exact model combination before you sign.
- One per premises: only one battery system per property is eligible for the federal discount, and it must stay installed for the warranty period or until the end of 2030, whichever is later.
What installation involves
We start with a site visit. We inspect your existing solar, the switchboard and the space where the battery and inverter would go, and we talk through how your home uses power so the size is matched to the load. We check whether your current inverter is on the iStore S1 compatibility list or whether a hybrid inverter change is part of the job, and we agree where the stack goes: typically a shaded, ventilated wall in a garage or on a sheltered outside face.
Before the install we lodge the network application with Western Power and Synergy, and the battery system is checked against the Synergy Supported Solutions List. On install day the technicians mount the modules and inverter, run isolators and cabling, and commission the system to AS/NZS 5139. We connect the battery to the iStore monitoring platform (a warranty requirement) and walk you through the app before we leave. One practical tip: keep the Wi-Fi connected to the battery, and let us know early if it ever drops off, so the monitoring record stays unbroken.
Things to know before you buy
Pros
Modular stack: start with one module and add more up to three per stack, with up to four stacks per compatible inverter (82.8 kWh).
15-year warranty backed by a throughput figure of 28.84 MWh at 60% end-of-life, so you can model the duty cycle rather than guess.
Lithium iron phosphate (LiFePO₄) cells and an IP66 rating, which allows a sheltered outdoor install if your site needs it.
Part of a broader iStore range (hybrid inverter, EV charger), which owners commonly cite as a strength when planning future upgrades.
Things to consider
You can’t buy the battery on its own. The iStore S1 battery needs a compatible iStore hybrid inverter to charge and discharge. If your current inverter isn’t on that list, factor an inverter change into the quote.
Blackout backup needs separate equipment. With a compatible iStore inverter and backup gear, the battery can supply selected essential circuits during an outage.
Monitoring must stay connected for the warranty. It is a requirement of the warranty that the battery is connected to the iStore monitoring platform. We set it up at commissioning; keep the Wi-Fi on and let us know if it drops out.
The install has a 31-day window. Under the warranty, the installation must be completed within 31 days, so delays after delivery matter. We book the install date before the hardware is on site.
Single-phase inverter choice limits scale. The IS-HYB-5000-1PH and IS-HYB-6000-1PH support one stack only. If you expect to grow past about 20.7 kWh usable, pick a larger inverter from the start rather than replace it later.
iStore battery questions Perth homeowners ask
Are iStore batteries any good?
The iStore S1 is a lithium iron phosphate battery with a 15-year warranty based on 28.84 MWh throughput at 60% end-of-life. Owners commonly point to the modular design as a strength, with the main consideration being that it needs a compatible iStore hybrid inverter and a separate backup box to run during an outage.
How much is an iStore battery?
Installed price depends on which stack you choose (6.9, 13.8 or 20.7 kWh usable), the hybrid inverter it pairs with, your switchboard, backup wiring and whether you add other components. We give a written quote after a site visit.
Does Istore do battery replacement?
The iStore S1 battery and its power module carry independent warranties. Where a warranty claim is confirmed under RMA, hardware support for the battery is provided within 20 calendar days. We handle the claim with the supplier.
What are the top 3 battery brands?
There isn’t a single correct answer: the right battery depends on your household load, the inverter you want and whether you need backup. We don’t rank brands on this page. We install the iStore S1 range covered here.
How long will a 10kW battery power my house?
That depends on how much your home actually draws. For example, a household using around 7 kWh over the evening would get through the night on the 13.8 kWh IS-BATT-14000-S1 stack with headroom; a bigger load would want the 20.7 kWh IS-BATT-21000-S1.
Is it better to have more solar panels or a bigger battery?
If you export a lot of daytime solar and buy power back at night, a bigger battery usually gives the better return. If your solar often can’t cover daytime use, extra panels come first. We go through your bills at the site visit before recommending a size.