Adding a Battery to Your Existing Solar: What Sydney Homeowners Need to Check

By the SimpliSolar team · Published 3 November 2026

If you already have solar panels, a battery is usually the next step. Most Sydney homes with solar export a large share of their daytime power for a few cents per kWh, then buy it back in the evening at peak rates. A battery stores that midday surplus and uses it after sunset instead.

Almost any existing system can take a battery, but the best way to do it depends on four things: the age and type of your inverter, how much surplus your panels produce, your switchboard, and whether you want backup power in a blackout. This guide walks through each one, the three ways a battery can be added, and how the federal battery discount applies to homes that already have solar.

Does the battery rebate apply if I already have solar?

Yes. Under the federal Cheaper Home Batteries Program, the Clean Energy Regulator says an eligible battery must be installed with either a new or an existing solar system. You do not need new panels to claim the discount. The other conditions still apply:

• The battery must be new and on the Clean Energy Council approved battery list.
• It must be installed by a Solar Accreditation Australia (SAA) installer with a battery endorsement.
• A grid-connected battery must be technically capable of joining a virtual power plant (VPP).
• Nominal capacity must be between 5 and 100kWh, and only the first 50kWh of usable capacity earns certificates.

For installs between May and December 2026, a 16kWh battery earns about 103 STCs (roughly $3,900) and a 28kWh battery about 152 STCs (roughly $5,800) at around $38 per STC. We take the discount off your invoice. See the battery rebate guide for the tiers and step-down dates.

The three ways to add a battery

1. Replace your inverter with a hybrid inverter

A hybrid inverter runs your panels and the battery from one box. The panels charge the battery directly as DC power, which avoids an extra conversion step. This is usually the best option when your current inverter is more than about eight to ten years old, out of warranty, or already showing faults, because you would be replacing it soon anyway.

2. Keep your inverter and add an AC-coupled battery

An AC-coupled battery has its own built-in inverter and connects on the AC side of your switchboard, next to your existing solar inverter. Your current system keeps working as it is. This suits homes with a newer inverter, homes with microinverters (where each panel has its own small inverter), and owners who want to keep their existing warranties intact.

3. Add modules to a battery-ready system

Some systems installed in the last few years already have a hybrid inverter. In that case the battery modules can often be added without changing the inverter, as long as the battery is compatible with that inverter brand and the inverter is large enough for the capacity you want.

Check 1: your inverter

Look at the label on the inverter, usually on a garage or side wall. Note the brand, model and size in kW, and roughly when it was installed. String inverters commonly last 10 to 15 years. If yours is close to that age, putting money into a hybrid replacement now often makes more sense than adding an AC-coupled battery to an inverter that may fail in a few years.

If the inverter is fairly new and reliable, keeping it and adding an AC-coupled battery is usually cheaper and simpler.

Check 2: is there enough surplus to charge the battery?

A battery only saves money if your panels produce more than you use during the day. As a rough guide, a north-facing system in Sydney averages around four kWh per kW of panels per day across the year, more in summer and less in winter. A 6.6kW system therefore produces in the order of 25kWh on an average day. If the house uses 8 to 10kWh while the sun is up, about 15kWh is left to charge a battery.

Older 3 to 5kW systems often do not produce enough surplus to fill a large battery, especially in winter. In that case it can be worth adding panels at the same time, either on a new hybrid inverter or as a separate small system, subject to roof space and your network’s export rules.

Check 3: your switchboard

Older Sydney homes, particularly those built before the 1990s, may still have ceramic fuses or a switchboard with no spare space. Adding a battery, especially with backup circuits, may need a switchboard upgrade with modern circuit breakers and RCD safety switches. We check this at the site visit and list it on the quote, so it is not a surprise on installation day.

Check 4: do you want blackout backup?

A battery does not automatically power your home in a blackout. Backup needs a battery and inverter that support it, plus wiring that separates the circuits to be backed up. Some AC-coupled batteries offer backup and some do not, so decide before you choose the product. Our blackout backup guide explains essential-circuit and whole-home options.

Approvals, feed-in tariffs and warranties

Adding a battery is treated as a change to your system, so a new connection application goes to your network (Endeavour Energy, Ausgrid or Essential Energy). The approval confirms your export limit. We lodge it for you.

NSW’s old premium feed-in tariff, the Solar Bonus Scheme, closed at the end of 2016, so there is no premium rate to lose by modifying your system. Your retailer’s normal feed-in rate continues, and with a battery you simply export less.

If another company installed your panels, their workmanship warranty may not cover changes made by a different installer. Panel manufacturer warranties are generally unaffected. Keep your original paperwork, and we will note on our quote exactly which parts we are changing.

What does it cost?

Costs depend on the battery size, whether the inverter is replaced, switchboard work and backup wiring. Our battery packages start from $5,499 with the federal discount applied, and every quote is fixed in writing after a site visit. See current options on our home batteries page.