STCs apply to additional capacity — not just new systems. When you add panels or replace an inverter, federal Small-scale Technology Certificates reduce the cost of the new equipment, just as they do on a fresh installation.
Solar Panel & Inverter Upgrades
Melbourne
Your electricity bills have risen, your household has grown, or you've added an EV. Your original 3kW or 5kW system was right for 2015 — it's not right for 2026. Supply Solar upgrades existing systems of any brand, age, or size.
Get a Free Upgrade Assessment
We check your existing system & design the right upgrade.
Three Upgrade Options
Which Solar Upgrade Path Is Right for You?
There is no single upgrade approach — the right option depends on your existing inverter's capacity, your system's age, your roof space, and what you want to achieve. Supply Solar assesses all of these before recommending a path.
Add Panels to Your Existing Inverter
When: your inverter has DC headroom remaining
If your current inverter's rated DC input is larger than your existing panel array, you may be able to add more panels to the same inverter — no new inverter required. For example, a 5kW inverter with 4kW of panels has 1kW of headroom where additional panels could be added (up to the inverter's maximum DC input).
Install a Second System Alongside
When: existing inverter is at capacity or still working well
The most common upgrade approach — a second inverter and additional panels installed alongside your existing system. Your original system continues running unchanged. The second system is a completely separate solar installation on available roof space, with its own inverter and grid connection.
Replace the Whole System
When: existing inverter is old, faulty, or system was very small (1.5–3kW)
If your original system was installed before 2015 with a 1.5kW–3kW inverter, the inverter is likely out of warranty, approaching end of life, or too small to be worth preserving. A full replacement — new panels and new inverter sized correctly for today — is often more cost-effective than patching an old system.
Can I Add Panels to My Existing Inverter?
Example A — Has headroom
Example B — No headroom
The DC oversize ratio rule: Most inverters accept up to 133% of their rated AC output as DC input — meaning a 5kW inverter can typically accept up to ~6.65kW DC. Your existing panels count against this limit. Supply Solar calculates the exact headroom for your specific inverter model.
The Technical Answer
Can I Add More Panels to My Existing Solar System?
This is the most common question Supply Solar receives about solar upgrades — and the answer is: it depends on your inverter's headroom. Here's how the technical assessment works.
Step 1 — Check your inverter's rated capacity
Your inverter has a rated AC output (e.g. 5kW) and a maximum DC input. The DC input is usually 133% of the AC rating — so a 5kW inverter accepts up to ~6.65kW DC from panels.
Step 2 — Calculate what's already connected
Add up the STC output of your existing panels. If that's already close to 6.65kW on your 5kW inverter, there's little or no headroom for more panels without exceeding the DC input limit.
Step 3 — Network approval for total system size
Even if headroom exists, adding panels increases your total system size — which requires a new or amended grid connection approval from your Victorian network distributor. Supply Solar manages this application.
Supply Solar does this assessment for free
We check your inverter model, calculate exact headroom, assess your roof space, and tell you clearly which upgrade path makes sense — before you spend anything.
Should I Upgrade My Inverter?
When to Replace Your Solar Inverter
Inverters are the component most likely to need replacement in a residential solar system. A 10-year-old inverter may still be running — but it could be costing you output or blocking a larger system upgrade.
Inverter is out of warranty
Most inverter warranties are 5–10 years. An out-of-warranty inverter failure means a full replacement cost with no manufacturer support. Proactive replacement is often more economical than reactive emergency repair.
Recurring error codes or faults
An inverter that repeatedly trips offline, shows grid fault codes, or requires manual restart has a hardware or firmware issue. Persistent faults that service can't fix mean replacement is the most reliable solution.
No monitoring or smart features
Older inverters from 2010–2016 often have no monitoring app, no real-time output data, and no battery-ready output. Replacing with a modern hybrid inverter opens the door to battery storage without extra equipment.
You want to add a battery
Most residential batteries require a compatible hybrid inverter — not just any solar inverter. If your existing inverter isn't battery-compatible, replacement is required before a battery can be added. Supply Solar quotes inverter replacement as part of every battery installation assessment.
Inverter Brands We Replace
We Replace All Inverter Brands
Supply Solar replaces inverters on all brands of residential solar systems — regardless of original installer. We assess the existing system, recommend a compatible replacement, and manage the grid connection amendment where required.
Inverters we regularly replace
Replacing a failed or outdated inverter with a modern hybrid model allows you to add a battery later — without any additional inverter cost at that stage.
Is It Worth Upgrading a 5kW to 10kW?
What to Do with Your Old Melbourne Solar System
Melbourne saw a solar boom in 2010–2014. Many of those 1.5kW, 2kW, and 3kW systems are still running — but are they right for today's household energy use? Here is honest guidance for common scenarios.
1.5kW–3kW system, installed pre-2016
Usually replace5kW system, inverter still working
Assess inverter age6.6kW system, bills still high
Add battery firstAny size system, inverter failed or failing
Replace and upgradeAdded an EV or ducted air conditioning
Size up to matchSTCs on Upgrade Work
Do STCs Apply to Solar Upgrades?
Yes — federal Small-scale Technology Certificates apply to the additional capacity being added, not just fresh installations. Here's how this works for the three upgrade paths.
STCs on New Capacity Added
Adding panels to an existing inverter: STCs apply to the new panels' capacity. If you add 2kW of panels, STCs are calculated on 2kW of new generation capacity in Melbourne's Zone 4.
Second system: STCs apply to the full capacity of the second system — treated as a new installation for STC purposes.
Full replacement: STCs apply to the full new system capacity. If you replace a 3kW system with a 10kW system, STCs are calculated on 10kW — not just the 7kW difference.
Solar Homes rebate: If you previously claimed the Solar Homes rebate on the original system, you cannot claim it again on the same property. STCs are separate and unaffected.
Do I Need Network Approval to Upgrade?
Do I Need Approval?
Network Approval for Solar Upgrades in Victoria
Adding panels or replacing an inverter with a larger one requires a fresh application to your Victorian network distributor. Supply Solar handles this entirely — here's the process.
Free upgrade assessment
We confirm your existing system size, inverter headroom, 3-phase status, and which approval type your upgrade requires.
Application lodged
Supply Solar lodges your grid connection amendment application to your network distributor before installation begins.
Approval confirmed
Once approval is received (typically 4–10 weeks), installation is scheduled. We manage any queries from the distributor.
Upgrade installed
Panels, inverter, or second system installed by our CEC-accredited team. All works certified and documented.
From Quote to Switch-On
How a Supply Solar Upgrade Works
Every upgrade starts with an honest assessment of your existing system. We tell you what will work and what won't — before quoting anything.
Free System Assessment
We review your existing inverter, panel count, roof space, and consumption. We identify which upgrade path is technically viable and most cost-effective.
Written Upgrade Proposal
A detailed quote showing new components, STCs applied, network approval requirements, and projected additional generation from the upgrade.
Grid Approval (if required)
Supply Solar lodges the network approval application and manages the distributor relationship. You are updated on progress throughout.
Installation & Commissioning
Upgrade installed by our CEC-accredited team. New generation is verified on the day and compared against pre-upgrade output.
Why Supply Solar
Accredited, Honest, & Fully In-House
Solar upgrades require technical knowledge beyond a standard install. Supply Solar's team assesses before quoting — we won't sell you an upgrade that won't work.
Industry Recognition
Solar Upgrades Near You
Melbourne & Regional Victoria
Supply Solar upgrades existing solar systems across all of Melbourne and Regional Victoria from our Cranbourne base.
What Customers Say
Solar Upgrade Reviews — Melbourne
"Had a 3kW system from 2012. Supply Solar assessed it, told me honestly the inverter wasn't worth preserving, and quoted a full 10kW replacement. The new system generates three times the output. Bills have dropped massively."
"We got an EV and our existing 5kW wasn't covering the charging. Supply Solar checked the inverter headroom, found we could add 1.5kW of panels without a new inverter, and the whole job was done in a day. Perfect solution."
"Inverter failed after 9 years. Supply Solar came out, confirmed replacement was needed, quoted a 10kW hybrid ready for battery. Whole thing handled from assessment to grid approval to install. Very professional."
FAQ
Solar Upgrade Questions
Related Services
Complete Your Home Energy Upgrade
Add Battery Storage
Store your solar surplus for overnight use. GoodWe ESA, Sigenergy, and Sungrow. Federal battery rebate applied. Works best after a solar upgrade.
View battery storage →Solar Maintenance
Before upgrading, understand your existing system's condition. A maintenance visit identifies faults, soiling, and whether an upgrade is the right next step.
View solar maintenance →New Solar Systems
If your existing system is beyond economic repair, explore new 6.6kW–20kW residential solar systems with full STC and Solar Homes rebates.
View solar systems →Ready to Upgrade Your
Solar System?
Supply Solar assesses your existing system, calculates inverter headroom, identifies the right upgrade path, and handles network approvals — all included in a free upgrade quote.