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.
How to use this calculator
- Enter your daily electricity usage — find your quarterly kWh on your electricity bill and divide by 90 to get a daily figure. The average Australian household uses 15–25 kWh/day.
- Select your state or territory — this sets the average peak sun hours for your region, which is the key variable in system sizing. Queensland and the NT receive significantly more solar irradiance than Victoria and Tasmania.
- Choose a panel wattage — 400 W is the most common residential size in 2026. Higher wattage panels generate more power per panel but cost more each.
- Optionally add battery storage — tick the checkbox and enter your preferred battery capacity in kWh to include battery cost in the estimate.
- Click "Calculate system size" to see your results.
Worked example: A Sydney household uses 20 kWh/day. State: NSW (4.5 peak sun hours). Panel: 400 W. System size = 20 ÷ 4.5 ÷ 0.77 = 5.77 kW, rounded up to 6.0 kW. Panel count = 15 × 400 W panels. Annual output = 6.0 × 4.5 × 365 × 0.77 ≈ 7,593 kWh/year. Install cost ≈ $7,200 before rebate. STC rebate ≈ $2,220. Estimated net cost ≈ $4,980.
Understanding your results
The recommended system size is the minimum kW needed to offset your stated daily usage under average conditions for your state. It is rounded up to the nearest 0.5 kW, which is how installers quote systems. The actual system your installer proposes may vary depending on roof space, panel layout, and shading analysis.
The estimated annual output is how much electricity your system should generate in a typical year. In practice, output varies by 10–20% between seasons and years depending on weather, soiling, and system health. Use it for payback modelling, not as a guarantee.
The STC rebate is calculated using approximate STCs per kW for each state zone. The actual rebate depends on the current STC spot price, which fluctuates — check the Clean Energy Regulator website for the live price.
Common mistakes: Undersizing the system to reduce upfront cost, then running a large shortfall in winter; not accounting for shading from trees, chimneys, or neighbouring buildings; assuming feed-in tariffs will offset a poor self-consumption ratio; and not factoring in electricity consumption changes (EV charging, pool pump, air conditioning).
Solar PV installation guide for Australian homes
Australia is one of the best countries in the world for rooftop solar — high irradiance, strong government incentives, and a mature installer market. Here is what you need to know before committing to a system.
Roof orientation and tilt
North-facing panels at a tilt angle equal to your latitude produce maximum annual output. In practice, east or west-facing panels generate 10–20% less output but shift generation into morning or afternoon, which may better match your household consumption profile. South-facing panels are generally not worth installing unless no other option exists. The calculator assumes average output across typical orientations — your installer's shade analysis will refine this significantly.
Network connection and export limits
Before installation, your installer must apply to your Distributed Network Service Provider (DNSP) — Ausgrid, Endeavour Energy, Energex, Western Power, SA Power Networks, etc. — for permission to connect. Most DNSPs allow up to 10 kW single-phase or 30 kW three-phase for residential systems without an upgrade. Many networks now impose export limits (often 5 kW per phase) in areas with high solar penetration. If your system is export-limited, self-consumption and battery storage become more valuable.
Choosing a CEC-accredited installer
Under the Small-scale Renewable Energy Scheme, all solar installations must be designed and installed by a Clean Energy Council (CEC) accredited installer to be eligible for the STC rebate. Check the accredited installer list at the CEC website before signing any contract. Get at least three quotes — prices vary significantly between installers. Be wary of "too good to be true" pricing, which often indicates inferior panels or inverters.
Panel and inverter quality
Panel brands are broadly categorised as Tier 1 (bankable, large manufacturers — Jinko, LONGi, Canadian Solar, REC) and lesser-known brands. Tier 1 classification relates to bankability for lenders, not necessarily quality. The inverter is often the most failure-prone component — major brands used in Australia include Fronius, SMA, Enphase, Sungrow, and Huawei. Enphase microinverters are popular for complex roof layouts or shaded roofs.
Battery storage considerations
In 2026, battery storage is increasingly viable in states with low feed-in tariffs and high peak electricity rates. A 10 kWh battery covers roughly 8–12 hours of typical evening household load. The Virtual Power Plant (VPP) programs offered by SA Power Networks, Energy Australia, and others can provide additional income by allowing your battery to export to the grid during peak demand events. Payback periods for battery-only additions are typically 7–12 years, shorter when combined with VPP participation.
Australian standards and references
- AS/NZS 5033:2021 — Installation and Safety Requirements for PV Arrays. Governs wiring, earthing, labelling, and fire safety of the PV array itself.
- AS/NZS 4777.1:2016 — Grid Connection of Energy Systems via Inverters (Part 1: Installation requirements). Sets requirements for inverter connection, protection settings, and disconnection.
- Clean Energy Council (CEC) Design and Installation Guidelines — Mandatory for SRES rebate eligibility. Covers system design, component selection, and installer obligations.
- Australian Government Small-scale Renewable Energy Scheme (SRES) — Federal incentive scheme administered by the Clean Energy Regulator. STC quantity is determined by system size, location zone, and years remaining in the scheme (closing 2030).
- AS/NZS 3000:2018 — Wiring Rules (applies to electrical connections between inverter, switchboard, and metering).
- NCC Volume 2 Section J — Minimum energy efficiency requirements for new homes; solar may contribute toward compliance.