One of the first questions on an STC form looks simple: is this a new system, a replacement or an additional one? It is also one of the most misunderstood. The answer drives eligibility, the paperwork you need and what an auditor will test later.
This guide explains the three types and how to record them. The details of eligibility rules can change, so the guidance reflects the position at the time of writing, and you should always confirm the current rule with the Clean Energy Regulator or the desk.
The three types at a glance
| Type | What it means | Typical example |
|---|---|---|
| New | No comparable system existed at the property | First solar system on a house |
| Replacement | An existing system is removed and a new one takes its place | Failed inverter and panels swapped for a new array |
| Additional | A new system or components added alongside an existing system | Second array or extra modules on an existing system |
The type is based on the physical situation at the property, not on what the customer calls the job.
Why the wrong choice causes rejection
Each type triggers different questions:
- A new claim at an address that already has a registered system is a red flag. The registry and the audit trail will show an earlier installation.
- A replacement claim without evidence that the old system was actually removed will be questioned.
- An additional claim may have limits on what can be claimed, or may need different paperwork, depending on the technology and the rules in force.
Picking the type that seems to produce the most certificates is the fastest way to a clawback. See how STC audits work for what happens when a certificate is later invalidated.
What to record about the old system
For any replacement or additional job, capture the following at the time of the install.
- Make and model of the existing system, where visible
- Approximate size or capacity
- Approximate age and installation date, if the owner knows
- Photos of the old equipment before removal
- What happened to it: removed, recycled, retained or relocated
- Why it was replaced or supplemented, for example failure, upgrade or battery addition
- Any earlier claim made for the old system, if the owner remembers
How the type affects STC eligibility
Solar PV
At the time of writing, a replacement of a small-scale solar system can be eligible in some circumstances, while additions to an existing system are treated differently. How much can be claimed depends on the rules for that situation. Check the current guidance before you quote the customer a discount. See the STC trading page for the overview.
Batteries
A battery added to an existing solar system is a common scenario. The solar system may already have claimed its certificates, and the battery is a separate claim with its own eligibility. The battery submission guide covers the paperwork, and the battery STC page covers the program context.
Hot water and heat pumps
Replacing an electric storage unit with a heat pump is the typical replacement. Record the old unit and make sure the new model is on the register. The hot water checklist has the detail.
A simple decision path
- Is there an existing system of the same kind at the address? If no, it is likely new.
- Is the old system being removed and taken out of service? If yes, it is likely a replacement.
- Is the old system staying in service while you add to it? If yes, it is likely additional.
- Does your situation not fit any of these? Call the desk before you lodge.
Keep the story consistent
The type you choose has to match everywhere: the assignment form, the invoice, the photos and the electrical certificate. If the form says replacement but the photos show no old equipment, the claim will stall.
Next steps
When you are not sure, we would rather hear from you before lodgement than after. The desk checks the installation type against your photos and paperwork as part of the pre-check described on how it works. Today’s rates are on the pricing page, and you can start trading when you are ready.