Solar Panel System Size Calculator AustraliaAS/NZS 5033
Your solar details
Check your electricity bill — divide quarterly kWh by 90 for a daily figure. Average Australian household uses 15–25 kWh/day.
Sets the average peak sun hours for your region.
Common residential batteries: Tesla Powerwall 13.5 kWh, Alpha ESS 10 kWh, Sungrow 9.6 kWh. A 10 kWh battery covers roughly 8–12 hours of evening/overnight usage.
Solar recommendation
System specifications
Estimated cost (AUD)
System size is calculated as: required kW = daily kWh ÷ peak sun hours ÷ 0.77 (system performance ratio). The performance ratio of 0.77 accounts for inverter efficiency losses, temperature derating, wiring losses and intermittent shading — consistent with industry standard assumptions used by CEC-accredited designers. Annual output = system kW × peak sun hours × 365 × 0.77. Peak sun hours represent the equivalent hours of peak solar irradiance (1,000 W/m²) per day for each state, averaged over the year.
Frequently Asked Questions
What size solar system does an average Australian household need?
The average Australian household uses about 18–22 kWh/day. For a Sydney household at 20 kWh/day, the recommended system size is approximately 5.8–6.6 kW — which is why 6.6 kW has become the de facto "standard" residential system size. In sunnier states like Queensland and Western Australia, you can cover the same usage with a slightly smaller system due to higher peak sun hours.
What is the Small-scale Technology Certificate (STC) rebate?
The STC rebate is part of the Australian Government's Small-scale Renewable Energy Scheme (SRES). When you install a solar system, you receive a number of STCs based on your system size, location (zone) and years remaining in the scheme. Installers typically take these STCs as an upfront discount off the purchase price. The value of each STC varies with the spot market — check the current STC price at the Clean Energy Regulator website for an accurate figure.
How many panels fit on a standard Australian house roof?
A standard residential roof can typically accommodate 20–30 panels depending on usable north-facing roof area, pitch, and setback requirements (AS/NZS 5033 requires a 300 mm gap from roof edges). At 400 W per panel, 20 panels = 8 kW and 30 panels = 12 kW. Most residential systems use 15–25 panels. Roof area is more often the limiting factor than electricity needs for large households.
Do I need council approval to install solar in Australia?
In most Australian states, residential rooftop solar is classified as exempt development under the National Construction Code and state planning legislation, meaning no development approval (DA) is required. However, some local councils, heritage overlays, strata buildings, and body corporate rules may impose additional requirements. Always confirm with your local council or body corporate before installation. Electrical connection still requires approval from your network operator (e.g. Ausgrid, Energex, Western Power).
Is battery storage worth it for an Australian household in 2026?
Battery economics depend on your feed-in tariff, time-of-use electricity rates, and household consumption patterns. In most states, feed-in tariffs have fallen significantly (often 5–10 c/kWh), while peak evening electricity rates are 35–55 c/kWh. This spread makes self-consumption valuable. A 10 kWh battery can store daytime solar generation for evening use, potentially saving $1,000–$2,000 per year depending on your usage profile. Payback periods in 2026 are typically 7–12 years for battery storage alone — shorter when combined with time-of-use tariffs and the right usage profile.