Adding a battery to existing solar
One question decides whether a battery retrofit is straightforward or expensive: what inverter do you already have? Any quote given before someone knows the answer is guesswork.
Retrofitting storage is one of the most common jobs in solar right now, and one of the most commonly mis-quoted. The panels aren't the issue. The inverter is.
The two ways a battery gets added
| Approach | When it applies | What it means for you |
|---|---|---|
| Hybrid / battery-ready inverter | Your existing inverter is already designed to take a battery | Usually the simpler path — the battery connects to what you have. Fewer boxes on the wall, lower cost. |
| AC coupling | Your existing inverter can't take a battery directly | A second, battery-dedicated inverter is added alongside. More equipment and more cost — but your working solar inverter stays put. |
Neither is "wrong". AC coupling is often the sensible answer when you've got a healthy inverter with years left in it — replacing it just to avoid a second box is rarely good value.
The photo that decides your price
The inverter nameplate — the label on the side stating make, model and rating — tells an installer whether it's hybrid-capable, how much headroom it has, and which batteries are compatible with it.
If you're being quoted for a battery and nobody has asked for that photo or looked at your inverter, the number you've been given is an estimate dressed up as a quote. It's also the single most common source of "unexpected variations" later.
If you already have a battery and want more
Some batteries stack — you add modules to what's there. Others don't, and a second separate system is needed. That depends on the specific brand and model, which is why the existing battery's nameplate matters just as much as the inverter's.
What changes about the rebate
Incentives are calculated on new capacity only — the kilowatt-hours you're adding, not the solar already on your roof. Battery incentives are also tiered, so a larger battery doesn't scale the benefit proportionally. Any quote showing a rebate against your existing system is wrong.
Adding panels to an existing system has its own specific rules about whether it counts as an extension or a new system — worth having your installer state clearly in writing which one they're claiming.
Questions that separate a real quote from a guess
- What make and model is my existing inverter, and is it hybrid-capable?
- Are you AC coupling, or connecting to the existing inverter?
- Is my switchboard adequate, or does it need an upgrade?
- Where will the battery go, and does that location meet the clearance rules?
- Does your accreditation include the battery endorsement?
That last one catches people out — solar accreditation and battery accreditation are separate. Here's how to check.
Get it checked properly, free
We photograph your existing inverter and switchboard before anyone quotes, so the design is based on your actual system — not an assumption. Then vetted installers price that same design and you choose.
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