Solar system sizing matches your roof, budget, DNSP export rules and electricity use — not your neighbour's Facebook array. In 2026, good sizing starts from interval data or bill kWh, then applies peak sun hours, self-consumption goals and optional battery plans under ~$372/kWh usable federal support. Bigger is not automatically smarter when export is capped.
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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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Read annual kWh and seasonal peaks. EV chargers, pools and all-electric hot water change the answer overnight. A 4-person home office house rarely matches a retiree couple's profile.
Use city peak sun hours and a realistic performance ratio. Sydney near 5.0 hours and Brisbane near 5.5 need different kWp to hit the same daily kWh. Ask for month-by-month estimates.
Usable area after setbacks, shade and fire/bushfire constraints caps kWp. Engineering for older roofs can matter more than module efficiency bragging rights.
If export is limited to 1.5–5kW (or 0kW), oversizing mainly helps if you self-consume or charge a battery. Model that explicitly before approving a 13kW array.
Size PV to create surplus for storage; size usable battery kWh to evening loads. Federal and state storage discounts improve affordability but should not tempt useless oversizing.
Fix your tariff and export assumption, then compare 6.6 vs 8 vs 10kW options from CEC-accredited installers via MrSolar. Pick the best bill outcome per dollar after STCs — Zone 3 6.6kW is about $1,435 federal discount at ~$39.85/STC (as of 5 August 2026).
Size solar to your bills and network limits — compare CEC-accredited options on MrSolar.
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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