Key points
- You have four main choices: add panels to your existing system, add a second system, replace everything, or add a battery.
- Federal STCs apply only to new panels that haven’t been claimed before. In 2026 a 3 kW addition earns roughly $800 in Adelaide or $680 in Melbourne, and the deeming period drops from 5 to 4 years on 1 January 2027.
- On SA’s legacy 44c feed-in tariff (ending 30 June 2028)? Adding a battery ends it, and going over your approved system size can too.
- Upgrades must meet current rules: Smarter Homes remote disconnection in SA and the emergency backstop in Victoria.
If you want to upgrade an old solar system, the right move depends on its age, its condition and the rules attached to it. A 1.5–3 kW system from the early 2010s often can’t keep up with a household that now runs air conditioning, an EV or a heat pump. You can add panels, install a second system alongside it, or replace it outright, and each choice has different rebate, tariff and network consequences. This guide compares them for South Australian and Victorian homes in 2026.
Is it time to upgrade your old solar system?
Common triggers we see:
- The system is small. Many early systems were 1.5–3 kW with panels of 250 W or less. A 2026 panel is typically 440–475 W.
- Your usage has grown. Electrifying your home with reverse-cycle air conditioning, induction cooking, a heat pump or an EV can double daytime demand.
- The inverter is ageing or has failed. If you’re paying for a new inverter anyway, it’s a natural time to reconsider the whole system. See when to replace a solar inverter.
- Panels are damaged or degraded. Normal ageing is slow, about 0.5% a year, so damage is a bigger reason. See how long solar panels last.
- You want a battery and need a battery-ready setup.
This guide is part of our complete guide to solar maintenance, repairs and upgrades.
Your options to upgrade an old solar system
| Option | What it involves | STCs (federal rebate) | Best when |
|---|---|---|---|
| 1. Add panels to the existing inverter | New panels wired to your current inverter | New panels only (“extension system”) | The inverter has spare capacity and is in good health |
| 2. New inverter, keep old panels and add new ones | Old and new panels connected to a new, larger inverter | New panels only (“extension system”) | Old panels are healthy but the inverter is due for replacement |
| 3. Add a second, separate system | New inverter and new panels alongside the old system | New system (“additional system”) | You want to keep the old system untouched |
| 4. Replace the whole system | Remove old gear, install a new inverter and panels | All new panels (“replacement system”) | The system is old, small or unreliable |
A fifth option is to leave the panels alone and add a battery. That’s covered in adding a battery to existing solar.
Option 1: Add panels to your existing inverter
This is the cheapest upgrade on paper, but it only works if your inverter has spare capacity. Many early systems were already sized close to the inverter’s limit. Panel capacity is generally capped at about 133% of the inverter’s rating for STC eligibility. New panels also rarely match old ones electrically, so they usually need their own string or input (MPPT) on the inverter. The Clean Energy Regulator (CER) requires the new panels and existing inverter to be on the Clean Energy Council approved list.
Option 2: New inverter with old and new panels
The CER allows a new inverter to run both existing and new panels. STCs are claimed only for the new panels. The catch is that an alteration usually means bringing the whole system up to current standards. The CER notes installers must upgrade any components that no longer meet requirements. Old rooftop DC isolators, cabling and earthing may need replacing, which adds cost.
Option 3: Add a second system
A separate new system leaves the old one untouched, which can be useful while it still earns a premium tariff. It’s eligible for STCs as an “additional system”. Your network will treat the combined capacity when setting export limits, and the new system must meet current connection rules.
Option 4: Start fresh
Replacing everything is simplest. You get one modern, warrantied system sized for your needs, with monitoring and battery-ready options. The CER treats it as a “replacement system”, so all-new panels are eligible for STCs. The old panels should go to recycling. For many 12- to 15-year-old systems this is the best long-term value.
What STCs can you get when upgrading?
STCs (small-scale technology certificates) are worked out as new panel kW × zone rating × deeming years. For installs in 2026 the deeming period is 5 years. With STCs trading around $39.85 in early October 2026, indicative values are:
| New panel capacity | Adelaide (Zone 3) | Melbourne (Zone 4) |
|---|---|---|
| 3 kW added | ~20 STCs (≈ $800) | ~17 STCs (≈ $680) |
| 6.6 kW added or replaced | ~45 STCs (≈ $1,800) | ~39 STCs (≈ $1,550) |
Important rules from the CER:
- Panels that have already been used to claim STCs can’t be claimed again.
- Replacing only some panels while keeping the existing inverter isn’t eligible for STCs.
- If you expand a system before its original STC claim is approved, you risk losing the STCs.
From 1 January 2027 the deeming period falls to 4 years, cutting STCs by about a fifth. Our guide to how the STC solar rebate is calculated has the full formula.
Upgrading in South Australia: the 44c tariff and Smarter Homes
If your system was connected under SA’s original feed-in scheme, you may still receive the legacy 44c/kWh distributor feed-in tariff. The SA Government says it continues until 30 June 2028 if you don’t upgrade or alter your system. It warns that any changes to your system could affect your eligibility, and that installing an energy storage device (a battery) ends the 44c payment.
Industry guidance is that you can generally add panels up to the capacity on your SA Power Networks permission to connect without losing the tariff, but going over it loses 44c for the whole system. A replacement inverter generally needs to be the same capacity or smaller. Get written confirmation from SA Power Networks before changing anything.
Worked example (hypothetical): a 1.5 kW system exporting 4 kWh a day at 44c earns about $1.76 a day, or around $640 a year. From November 2026 to the end of June 2028 that’s roughly $1,000 more. Some owners keep the old system untouched until mid-2028 and plan a full replacement or battery then. Others find a bigger new system saves more sooner. Run the numbers for your own usage.
New or upgraded SA systems must also meet Smarter Homes rules. SA Power Networks says new solar must be able to be remotely disconnected, and an existing system installed before 28 September 2020 only needs this if its inverter is replaced (same-model warranty swaps are exempt). Upgraders can usually choose flexible exports of up to 10 kW per phase instead of a fixed 1.5 kW per phase. See our Adelaide solar guide for local detail.
Upgrading in Victoria: rebates and the emergency backstop
Solar Victoria’s solar panel rebate (up to $1,400, plus an optional interest-free loan) requires that the address hasn’t had a solar system installed in the last 10 years. Solar Victoria says that if your system is 10 or more years old, you might be eligible to use the rebate to replace or expand it. Other rules apply, including a $150,000 household income cap from 1 July 2026 and a property value under $3 million. You must get eligibility approval before installation.
Since 1 October 2024, Victoria’s emergency backstop applies to new systems and to upgrades. Solar Victoria lists more panels, a change of panel type or inverter (except like-for-like replacement) and adding a battery as changes that trigger the requirement. Victoria’s old premium feed-in tariffs have ended and there’s been no minimum feed-in tariff since 1 July 2025, so most upgrades are now about self-consumption. See our Melbourne solar guide.
How to decide: a quick checklist
- Find your paperwork: installation date, panel and inverter models, and (in SA) your permission to connect.
- Check condition: have a licensed electrician inspect and test the panels, isolators and inverter.
- Check your usage: look at a year of bills or smart meter data, and allow for future EVs or electrification.
- Check roof space: modern panels may let you fit far more capacity in the same area.
- Price at least two options side by side, such as adding panels versus a full replacement, including STCs, network rules and tariff impacts.
For many families, replacing an old 1.5–3 kW system with a modern 10kW solar system more than triples the generating capacity, often on the same roof.
Frequently asked questions
Can I add more solar panels to my existing system?
Often, yes, if your inverter has spare capacity, the new panels suit its electrical limits and there’s roof space. The new panels may be eligible for STCs as an extension. An installer must check the old system meets current standards. Adding panels can trigger new network rules and, in SA, may affect a legacy 44c feed-in tariff.
Can I mix old and new solar panels?
Yes, but not on the same string in most cases. Old and new panels have different voltages and currents, so mixing them on one string drags the whole string down to the weakest panel. Installers usually put new panels on a separate string or inverter input, or install a separate inverter for them.
Will upgrading my solar affect my 44c feed-in tariff in SA?
It can. The SA Government says changes to your system could affect eligibility, and installing a battery ends the 44c payment. Industry guidance is that going beyond the capacity on your permission to connect loses the tariff for the whole system. The scheme ends on 30 June 2028, so confirm any change with SA Power Networks first.
Is it better to upgrade or replace an old solar system?
If the system is over 10 years old, small and has an ageing inverter, a full replacement is often better value, because all-new panels attract STCs and you get fresh warranties and modern monitoring. If the inverter is newer with spare capacity, adding panels can be cheaper. Compare quotes for both.
Our Adelaide and Melbourne installers can test your existing system, check your permission to connect or rebate eligibility, and quote add-on and replacement options side by side. Contact us for an upgrade assessment.
Sources: Clean Energy Regulator – Small-scale renewable energy systems (expanding, upgrading or replacing) (accessed Oct 2026); SA.GOV.AU – Solar feed-in payments; SA Power Networks – Relevant Agent FAQs (accessed Oct 2026); Solar Victoria – Solar panel rebate (accessed Oct 2026); Victorian Government – Emergency backstop customer factsheet (2024). STC values are indicative and move with the market; tariff and network rules change, so confirm with your network and installer before upgrading. Featured image: Martin Dawes / Wikimedia Commons, CC BY-SA 2.0.
