Adding a Battery to Your Existing Solar System: The Step-by-Step Process

Adding a battery to an existing solar system is a common upgrade, and in most Sydney homes it can be done without touching the panels. The process runs in a set order: we record the solar you already have, decide whether to keep your inverter or replace it with a hybrid, confirm the switchboard can take the new equipment, apply the federal battery discount, lodge the network application, then install and commission. Knowing each step helps you ask the right questions and spot anything missing from a quote.

Step 1: Check the solar you already have

Your existing system shapes almost every decision that follows, so the first job is to document it properly.

• Inverter make, model, age and condition. An inverter near the end of its working life is a poor foundation for a new battery.
• System size and panel layout. The surplus your array produces sets how much battery it can realistically fill, especially in winter.
• Existing approval and export settings. The original network approval and any export limit carry through into the new design.
• Monitoring. Whether your system measures household consumption, or only production, affects how precisely we can size the battery.
• Paperwork. Warranty documents, the original certificate of compliance and any service reports.

If you have a monitoring app, screenshots of a typical summer day and a typical winter day are genuinely useful. Our battery-only calculator gives a first estimate of the capacity that suits your usage before anyone visits.

One honest check at this stage: is the existing array big enough to fill a battery? Older 1.5 kW or 3 kW systems often produce little more than a household uses during the day, especially in winter, leaving not much surplus to store. In that case, adding panels or replacing the system at the same time as the battery can give a far better result than storage alone, and we will say so on the quote.

Step 2: Keep your inverter or swap to a hybrid

There are two main ways to connect a battery to an existing system. With AC coupling, the battery comes with its own inverter and connects at the switchboard, leaving your solar inverter where it is. With a hybrid swap, the old solar inverter is removed and one hybrid inverter runs both the panels and the battery. Our home battery page covers the technical differences. For a retrofit, the decision usually comes down to these practical factors.

We install Sigenergy, GoodWe, Fox ESS and Sungrow batteries and hybrid inverters, which lets us match the approach to the equipment already on your wall rather than forcing the same answer on every home.

Step 3: Switchboard, location and cabling

A battery needs new protection devices in the switchboard, a sensible cable route and a compliant location. Older switchboards with ceramic fuses, no spare space or a backing panel that may contain asbestos often need an upgrade first. If you want blackout backup, the board may also need to be split so that selected circuits stay on when the grid goes down.

Location matters as much as capacity. Batteries have siting, clearance and ventilation requirements, and they are happiest out of direct afternoon sun, which is why garages and shaded side walls are common choices. All switchboard and cabling work must be carried out by a licensed electrician, and we show it as a separate line on the quote so you can see exactly what it covers.

Step 4: Apply the federal battery discount

The federal Cheaper Home Batteries Program takes roughly 30% off the installed cost of a home battery, delivered through STCs. The battery must be installed with solar, and existing solar qualifies. The discount is tiered by capacity:

• approximately $272 per kWh for the first 14 kWh;
• approximately $163 per kWh from 14 to 28 kWh;
• approximately $41 per kWh from 28 to 50 kWh.

The battery must be on the approved products list and installed by an SAA-accredited installer, and the installer creates the certificates so the discount comes off at the point of sale. The per-kWh value steps down every 1 January and 1 July to 2030, so check the current figures on the Clean Energy Regulator's program page before you sign. For most NSW households, the separate NSW battery installation incentive no longer stacks with it, because it has been suspended since 30 June 2025. Our federal battery rebate guide goes into more detail.

Step 5: Network approval

Before installation, the design goes to your local electricity network for approval. The application covers the total inverter capacity on the property, the export limit and how export control will work. A battery can change those numbers, particularly with AC coupling, where two inverters share one connection. Approval times vary between networks, and occasionally the network attaches conditions such as a lower export limit. We prepare, lodge and follow up the application for you.

Step 6: Installation and commissioning

A straightforward battery retrofit is often completed in a single day, although switchboard upgrades or long cable runs can extend that. Commissioning is where the system is set up to suit your household:

1. firmware updated and the battery registered for warranty;
2. grid settings and export limit configured to match the approval;
3. operating mode, backup reserve and any tariff windows set;
4. blackout changeover tested where backup circuits are installed;
5. monitoring app connected and explained to you;
6. certificate of compliance and handover documents supplied.

Your retailer may also need to reconfigure or exchange the meter. We coordinate that step, although its timing depends on the retailer's metering provider.

Next steps

In our energy market, Add a Battery to Existing Solar is listed from $8,990 for a 10 kWh class battery, installed. That price is indicative and confirmed after a site assessment, because your inverter, switchboard and battery location all shape the final scope. When you are ready, request a quote and include a photo of your inverter label and a recent electricity bill so we can prepare properly for the visit.

Frequently asked questions

How long does the whole process take, from quote to switch-on?

The longest waits are usually network approval and equipment availability rather than the installation itself. For a straightforward home, the process commonly takes a few weeks from an accepted quote to switch-on, and longer if a switchboard upgrade, meter change or extra approvals are involved. We give you an expected timeline with the quote and keep you updated if anything on the network side changes.

Will my solar keep running while the battery is installed?

Not for the whole day. For safety, the solar system is shut down while our electricians connect the battery, and power to the house is switched off for part of the job when switchboard work is needed. We explain the expected outage window before we arrive so you can plan around it, for example by keeping the fridge closed and avoiding important video calls.

Can I start with a smaller battery and add capacity later?

Often, yes, if you choose a modular battery designed for expansion. Adding modules later depends on the model still being supported, firmware compatibility and available space. Our market lists a Battery Expansion Module from $3,490 per module, installed, and the federal discount may apply to added capacity. If you already expect to need more storage within a year or two, it is usually simpler to size for that from the start.