About a third of the battery quotes we write are for households that already have solar and want to add storage without ripping out what's working. The right approach depends almost entirely on what inverter you already have, how old it is, and whether it's worth keeping. This guide is for that specific situation, not for a ground-up new install.
AC-coupled vs DC-coupled, explained simply
Your solar panels produce DC (direct current) power. Your house runs on AC (alternating current). The inverter converts one to the other. Where a battery fits into that conversion chain determines whether the setup is "AC-coupled" or "DC-coupled," and each has different implications for cost, efficiency, and compatibility.
Path A
AC-coupled: keep your existing inverter, add a battery alongside it
The battery sits on the AC side of your existing system. Your solar inverter does its job as normal, converting panel DC to house AC. The battery has its own built-in inverter that converts AC back to DC for storage, and DC back to AC when you use it. This means the stored power gets converted twice (AC to DC to AC), losing a few percent of efficiency each time, roughly 10% round-trip loss compared to DC-coupled.
The upside: your existing solar inverter doesn't need to be touched. The battery works alongside it, regardless of brand or age, as long as it's still functional and CEC-listed. Installation is typically simpler and cheaper because you're adding a box to the wall, not rewiring the solar array.
Path B
DC-coupled: replace your inverter with a hybrid, add a battery to it
The battery connects directly to a new hybrid inverter on the DC side, before the conversion to AC. Solar DC power charges the battery directly, only converting to AC once when you use it. This is more efficient per cycle (roughly 5% round-trip loss) and gives you a single system with one app, one warranty relationship, and tighter integration.
The downside: you're replacing your existing inverter, even if it's still working. That adds $2,000 to $4,000 to the project cost depending on the hybrid inverter chosen, and it means rewiring the solar array to connect to the new unit. Your old inverter has no resale value.
Which batteries suit a retrofit?
Not every battery works for every retrofit. Here's how the brands we install map to the two paths above.
AC-coupled retrofit options (keep your existing inverter)
Enphase IQ Battery 5P — purpose-built for AC-coupling, works with any existing inverter brand. 15-year warranty, modular (add capacity incrementally). The cleanest retrofit option if you don't want to touch the existing solar at all.
FranklinWH aPower — AC-coupled battery with its own advanced inverter built in. 12 to 15 year warranty. Works alongside any existing solar inverter. Strongest backup output in this category.
Tesla Powerwall 3 — has an integrated hybrid inverter, but can also be configured as AC-coupled to work alongside an existing inverter. The most flexible single product in this category, though it's more cost-effective on a new install where you use its integrated inverter.
DC-coupled retrofit options (replace your inverter with a hybrid)
Sungrow SH hybrid + SBR battery — the value pick. Single-vendor stack, 10-year warranty on both, proven reliability. The go-to recommendation when the existing inverter is due for replacement anyway.
Sigenergy SigenStor — all-in-one tower with hybrid inverter, battery, and optional EV charger. 10-year whole-system warranty. Makes most sense when the retrofit is also the moment to add EV charging.
GoodWe ET/ES hybrid + compatible battery — strong local support from the Rowville office, 10-year warranty. A solid mid-tier alternative to Sungrow.
What it actually costs
AC-coupled retrofit (keep existing inverter): battery only, installed, after federal rebate: ~$8,000 to $12,000 for 10 to 14 kWh depending on brand. No inverter replacement cost, no panel rewiring. Simpler install, typically half a day.
DC-coupled retrofit (replace inverter, add battery): new hybrid inverter + battery, installed, after federal rebate: ~$12,000 to $18,000 for a 10 to 14 kWh system. This includes the new hybrid inverter, rewiring, and the battery. Full-day install. For which hybrid inverter we'd recommend, see our inverter ranking.
The price gap between the two paths is roughly $4,000 to $6,000, which is essentially the cost of the new hybrid inverter and the extra labour to rewire. That gap is only worth paying if your existing inverter is old, underperforming, or you want the tighter integration and efficiency of DC-coupling. For whether the battery itself pays back within its warranty, see our payback guide. And if you're wondering whether export limits and falling feed-in tariffs justify the investment, we cover that separately too.
The decision tree
Is your existing inverter less than 5 years old and working well? AC-coupled retrofit. Keep it, add a battery alongside it.
Is your existing inverter 8+ years old, out of warranty, or showing errors? DC-coupled retrofit. Replace it with a hybrid inverter and add a battery at the same time. You're going to need a new inverter soon anyway.
Is your existing inverter 5 to 8 years old? Judgment call. If it's performing well and from a reputable brand with ongoing support, AC-coupling saves you money now. If it's from a brand that's exited Australia or doesn't support modern grid requirements, replace it.
Are you also expanding the solar array? DC-coupled, almost always. A new hybrid inverter sized for both the existing and new panels, plus a battery, is cleaner than adding a second inverter and AC-coupling a battery to a multi-inverter system.
We assess your existing system before quoting a battery
We check your inverter model, age, firmware, export limit, and roof layout at the site assessment, not after you've signed. If your existing inverter is worth keeping, we'll say so. If it isn't, we'll explain why before quoting a replacement.
Book a site assessment or call 0450 980 005Common questions
This guide reflects retrofit approaches and pricing as at September 2026, cross-checked against current manufacturer compatibility documentation and the federal Cheaper Home Batteries Program rules. Reviewed by Gagandeep Gill before publishing. Pricing, product availability, and rebate terms change; confirm current details with us at quote stage.