Right-sizing beats max-sizing. Australian homes should match array capacity to daytime loads, roof real estate and DNSP export limits — then sanity-check the budget after STCs. This guide gives a practical method using bills, sun-hour context and common size bands (5kW, 6.6kW, 10kW), with 2026 price and rebate notes, before you compare CEC-accredited designs on MrSolar.
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Indicative 2026 pricing: a typical 6.6kW system often quotes around $5,000–$8,000 after the STC discount (metro installs often $5,000–$7,500; premium/regional can run higher). See our solar cost guide.
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Divide quarterly kWh by days, then separate rough day vs night usage if you have interval data. Households using 15–20 kWh/day often consider ~5–6.6kW; 25–35 kWh/day loads with pools or WFH may look at 8–10kW when the roof and network allow. Do not size solely to eliminate the bill to zero — export limits and FiTs of a few cents make that a poor objective. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Save PDFs of every plan, approval and datasheet — warranty claims years later depend on that trail.
As a planning aid, daily output ≈ system kW × peak sun hours × performance factor. Capitals differ: Perth and Darwin are strong; Hobart is softer; Brisbane, Adelaide and Sydney sit in a robust middle. A 6.6kW array might yield roughly 20–33 kWh/day before losses depending on city and season. Always derate for shade, orientation and soiling rather than using brochure maxima. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Photograph your switchboard and roof planes before quoting day to cut variation risk.
Usable unshaded area, rafter layout, number of roof faces and switchboard capacity often cap size before your ambition does. Single-phase export limits (commonly discussed around 5kW in constrained pockets, though rules vary) can make ultra-large arrays less useful without a battery. Three-phase homes unlock different options. A CEC designer should show a roof plan with stringing, not just a kilowatt number. A site assessment with photos, stringing plan and shade notes beats brochure layouts; mismatched orientations need separate MPPTs or module-level electronics. Save PDFs of every plan, approval and datasheet — warranty claims years later depend on that trail.
Larger systems create more STCs but cost more capital. At $39.85 as of 2026-08-05, Zone 3 6.6kW ≈ $1,435 STC value and Zone 4 ≈ $1,235 in MrSolar’s table. After STC, many metro 6.6kW quotes sit near $5,000–$8,000. If adding 3kW more panels only exports at 5c/kWh, the upgrade may fail the bill test unless a battery or EV will absorb the energy. Ask the installer to show the certificate or voucher maths with your postcode, the $39.85 spot assumption (as of 2026-08-05) where STCs apply, and a separate line for any Cheaper Home Batteries Program dollars (~$372/kWh usable since 1 July 2025). Photograph your switchboard and roof planes before quoting day to cut variation risk.
If an EV or battery arrives within two years, leave inverter and switchboard headroom. The Cheaper Home Batteries Program (~$372/kWh usable since 1 July 2025) improves storage economics, which can justify slightly larger PV when evening loads will rise. Avoid buying orphaned capacity “just in case” with no pathway to use it. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Save PDFs of every plan, approval and datasheet — warranty claims years later depend on that trail. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Photograph your switchboard and roof planes before quoting day to cut variation risk.
Ask installers for two size options (for example 6.6kW vs 10kW) modelled on your tariff. Compare self-consumption, export assumptions and upgrade costs. MrSolar helps you gather CEC-accredited proposals so sizing debates stay evidence-based. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Photograph your switchboard and roof planes before quoting day to cut variation risk. Keep decisions grounded in your interval data, roof constraints and written DNSP settings rather than national averages or salesperson screenshots. Save PDFs of every plan, approval and datasheet — warranty claims years later depend on that trail.
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Written and reviewed by Daniel (Marketplace lead, Epic Unicorn Pty Ltd). We build pages from Australian solar datasets and regulatory references, then map you to CEC-accredited installers only.
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