Australia's solar installation industry processes hundreds of thousands of residential and commercial installations per year, making it one of the highest-volume compliance environments for bookkeepers. The interaction between the Clean Energy Regulator's certificate schemes, the GST system, and consumer guarantee warranty obligations creates specific accounting requirements that differ materially from general trade contracting. Getting the STC treatment wrong means every installation is misposted — and the error compounds across a high-volume operation.
Small-Scale Technology Certificates: The Point-of-Sale Discount Mechanism
Small-scale Technology Certificates (STCs) are created under the Renewable Energy (Electricity) Act 2000 when a solar PV system is installed by a registered installer on a qualifying premises. The number of STCs is calculated using the system's output in megawatt-hours over a 15-year deeming period, based on the system's location and orientation.
In the most common commercial arrangement, the installer assigns the STCs to an STC agent (a registered trader, often the retailer or distributor) at the point of sale. In exchange, the agent provides a discount on the purchase price — the "point-of-sale rebate." The customer pays the net amount (system cost minus STC value).
The ATO's position on the GST treatment is clear: when an installer discounts the sale price in exchange for the assignment of STCs, the GST is calculated on the net discounted amount the customer pays. The STC assignment is not a separate taxable supply by the customer to the installer. If the customer pays $8,000 for a system whose gross price was $10,000 and the $2,000 difference was funded by STC assignment, the GST is 1/11 of $8,000 ($727), not 1/11 of $10,000.
The alternative arrangement — where the installer does not discount the sale but instead receives the STCs themselves and sells them separately on the STC market — is different. In that case, the installer receives STCs as consideration for part of the supply value. The market value of the STCs received must be included in assessable income, and GST is calculated on the full system price (including the STC component). Fewer installers use this arrangement but it does exist in some commercial solar transactions.
Large-scale Generation Certificates for Commercial Systems
For commercial or industrial rooftop systems above 100kW, the relevant certificate is the Large-scale Generation Certificate (LGC) under the Renewable Energy (Electricity) Act 2000. LGCs are created based on the actual generation of eligible generators in megawatt-hours and accredited under the Large-scale Renewable Energy Target (LRET).
For large-scale commercial solar installations, the system owner (the business, not the installer) typically retains and surrenders or trades the LGCs. The installer's revenue recognition is based on the installation contract price — the customer pays for the system and manages the LGC stream thereafter. In these cases, the installer's books are simpler: the full contract price is revenue (taxable supply, 10% GST), and the customer's subsequent LGC creation and trading is a separate matter.
Where an installer does enter into a contract that includes LGC creation and trading as part of the service bundle (for example, a power purchase agreement structure), the LGC component is a separate income stream — assessable at market value when certificates are created or sold, with GST on the LGC sale (they are taxable supplies).
Revenue Recognition on Installation Contracts
Most residential solar installations are straightforward: a single performance obligation (supply and install the system), satisfied when the system is installed, commissioned, and connection approval obtained from the distribution network. Revenue is recognised at the point of commissioning — AASB 15 point-in-time recognition.
Commercial installations with longer construction phases — large rooftop systems on industrial or agricultural sheds, multi-building installations, or multi-stage community solar projects — may involve contracts where revenue is recognised over time (AASB 15 percentage-completion) rather than at a single point. For these engagements, a WIP schedule should be maintained as for any construction contract, with progress claims billed against milestones and contract assets/liabilities recognised for any timing difference between billing and revenue.
GST on Battery Storage Add-Ons
Battery storage systems (e.g., Tesla Powerwall, SolarEdge, Fronius Primo hybrid systems) are taxable supplies — there is no GST-free treatment for battery storage equipment, even when sold as part of a solar installation package.
Where solar panels and batteries are sold as a bundled package, the entire bundle is a taxable supply at 10% GST. There is no legal basis for carving out the solar panel component as "clean energy infrastructure" with a reduced or zero GST rate — the GST Act does not contain such an exemption. Installers who structure invoices to allocate a disproportionate amount to hypothetically "GST-free" components are applying incorrect treatment and risk penalties on audit.
The STC discount mechanics described above apply to the bundled package price — the STC value is based on the solar component of the system (batteries do not generate STCs), so the STC calculation is done on the solar-only value within the bundle, but the GST calculation is on the net customer cash payment for the entire package.
Warranties and the Consumer Guarantee Provision
Under the Australian Consumer Law (ACL, Schedule 2 to the Competition and Consumer Act 2010), major components of a residential solar installation — the panels and inverter — carry consumer guarantee obligations for a period that reflects what a consumer would reasonably expect for such goods. Industry standard is effectively 10 years for panels and 5–10 years for inverters, based on manufacturer warranty periods and the reasonable consumer expectation standard.
For high-volume installers (50+ systems per month), a warranty provision should be recognised at balance date. The provision represents the estimated cost of future warranty call-outs and component replacements on systems already installed. Under AASB 137 Provisions, Contingent Liabilities and Contingent Assets, a provision is recognised when the entity has a present obligation (the warranty exists), it is probable that a transfer of economic benefits will be required, and the amount can be reliably estimated.
A reasonable methodology is to apply a historical warranty cost rate (total warranty costs incurred ÷ total systems installed in prior periods) to the current year's installations to estimate the provision. If the average warranty cost per system is $150 and 800 systems were installed this year, the provision is $120,000. Adjust the rate as actual experience develops.
End-of-Period Checklist for Solar Installer Bookkeepers
- Review all residential installations: confirm GST is calculated on the net customer payment (gross price less STC point-of-sale discount), not the gross system price
- Identify any installations where the firm received STCs directly (rather than providing a point-of-sale discount): include the market value of STCs received in assessable income and calculate GST on the full gross price
- Review commercial solar installations above 100kW: confirm LGC creation and trading income is recognised separately if the installer is involved in the LGC stream
- Confirm all battery storage sales are coded as taxable supplies at 10% GST — no GST exemption applies to clean energy equipment
- For contracts in progress at balance date: prepare WIP schedules and assess percentage completion; recognise contract assets or liabilities for timing differences
- Calculate the warranty provision at balance date using historical warranty cost rates; adjust the provision for any warranty call-outs resolved during the period
- Confirm EMDG receipts (if the firm exports solar technology or services) are coded as assessable income, not GST supplies