Adding a battery to an existing solar installation requires a site-specific assessment. It does not automatically require every existing photovoltaic component to be replaced, but it does require the existing system to be checked for safety and compatibility with the proposed battery and inverter arrangement.
Western Australia's Building and Energy division explains the distinction in its guidance on existing PV arrays and battery energy storage systems.
Repair versus alteration
A repair restores an existing component using a like-for-like replacement. The repaired component must meet the standard that applied when the original installation was completed. Building and Energy notes that using current standards is good practice where practicable.
An alteration changes, extends or upgrades the PV array, its components or its wiring. The altered parts must meet current standards and remain compatible with the parts that have not been altered.
A new or non-direct replacement inverter must comply with the current AS/NZS 4777 requirements identified by the regulator.
Existing arrays
Replacing an inverter with a compatible multi-mode inverter does not, by itself, require replacement of the existing PV array.
The array must still be visually inspected and tested to establish that it:
- remains safe
- was compliant with the requirements that applied when installed
- is compatible with the proposed inverter and battery arrangement
- is not made unsafe by the new work
Unsafe or non-compliant portions must be repaired or altered as required. Older installations may need more work, but age alone does not determine the outcome.
| Record | Standard basis | Assessment still required |
|---|---|---|
| Like-for-like repair | ●Standard applying to the original installation | ●Use current standards where practicable |
| Altered components | ●Current standards for the altered parts | ●Compatibility with parts that remain |
| Existing PV array retained | ●Compliance when originally installed | ●Visual inspection, testing, safety and compatibility |
This matrix summarises the distinctions in the retained WA guidance. It is not a site assessment or permission to retain unsafe equipment. Current standards, product compatibility, network and scheme requirements still apply.
Data table
| Record | Standard basis | Assessment still required |
|---|---|---|
| Like-for-like repair | Standard applying to the original installation (confirmed) | Use current standards where practicable (confirmed) |
| Altered components | Current standards for the altered parts (confirmed) | Compatibility with parts that remain (confirmed) |
| Existing PV array retained | Compliance when originally installed (confirmed) | Visual inspection, testing, safety and compatibility (confirmed) |
WA scheme requirements
For work under the WA Residential Battery Scheme, the existing site must also be compatible with current scheme requirements, including remote management capability where applicable.
The WA Government describes this as whole-of-site compliance. It may require changes to an existing inverter, wiring or other equipment, but the required work depends on the site's condition, configuration and supported equipment.
Customers assessing a retrofit can use the adding a battery to existing solar guide to understand the decisions that should be resolved before accepting a proposal.
Assessment sequence
Before proposing a battery retrofit, the responsible contractor should:
- identify the existing array, inverter, wiring and protection arrangement
- inspect and test the existing installation
- determine whether each required change is a repair or an alteration
- confirm product, network and remote-management compatibility
- document any work needed to make the completed system safe and compliant
- explain the scope and reason for any replacement or upgrade to the customer
Primary references
- Existing PV array compliance requirements when installing BESS (opens in a new tab)
- WA Battery Energy Storage Systems guidance (opens in a new tab)
- WA Residential Battery Scheme questions and answers (opens in a new tab)
- WA solar and battery compliance hub
This article summarises public guidance and does not replace an electrical inspection, the current standards, network requirements or scheme rules.
