The sunniest Australian cities are the worst places to put solar on your roof.

The contradiction

Perth generates 10,033 kWh a year against Adelaide's 9,624 kWh — more power from 4.9 peak sun-hours against 4.7. It still takes 43% longer to pay for itself: 4.51 years against 3.15. South Australians pay about 44c/kWh, the highest in the country, so every unit a panel offsets is worth more there than anywhere else.

The same inversion appears further down the table. Melbourne gets 10% more sun than Hobart and still finishes last of every Australian capital, because Tasmania's regulated 8c feed-in is higher than Victoria's 5c.

Capital city payback league table

A 6.6 kW system at $6,250 installed, 40% self-consumption, median metro suburb. Ranked fastest to slowest payback.

The spread between best and worst is 1.94 years, or 63%, for identical hardware on an identical roof.

Why it happens — payback tracks the gap, not the sun

A solar panel earns in two ways: power you use yourself, which saves the retail rate, and power you export, which earns the feed-in rate. The distance between those two numbers — the arbitrage — is what actually sets payback.

• SA — 44c usage, 5c feed-in, 39c arbitrage
• NSW — 34c usage, 6c feed-in, 28c arbitrage
• WA — 30c usage, 3c feed-in, 27c arbitrage
• QLD — 32c usage, 6c feed-in, 26c arbitrage
• VIC — 28c usage, 5c feed-in, 23c arbitrage
• TAS — 28c usage, 8c feed-in, 20c arbitrage
• ACT — 26c usage, 7c feed-in, 19c arbitrage
• NT — 28c usage, 10c feed-in, 18c arbitrage

SA's spread is 70% wider than VIC's, and the payback ranking follows the arbitrage ranking closely. The exceptions are Darwin and Brisbane, where sunlight is strong enough to overcome a narrow spread — the only place in this dataset where sunshine decides the outcome.

Regional Australia beats the capitals

• Cairns, QLD — 3.21 yr payback at 5.8 sun-hours
• Townsville, QLD — 3.32 yr payback at 5.6 sun-hours
• Newcastle, NSW — 3.62 yr payback at 4.9 sun-hours
• Dubbo, NSW — 3.62 yr payback at 4.9 sun-hours
• Wagga Wagga, NSW — 3.78 yr payback at 4.7 sun-hours
• Toowoomba, QLD — 3.65 yr payback at 5.1 sun-hours
• Bendigo, VIC — 5.00 yr payback at 4.3 sun-hours
• Ballarat, VIC — 5.00 yr payback at 4.3 sun-hours
• Geelong, VIC — 5.24 yr payback at 4.1 sun-hours

Within a single city there is almost no spread to find: 796 of Sydney’s 931 metro suburbs sit on the same 4.6 peak sun-hours. The variation that matters is between capitals, not inside them.

Solar still pays for itself in five years or less in every capital. Nothing in this data argues against installing. The finding is that the payback period varies by 63% between capitals for the same hardware, and that the variable driving it is not the one homeowners are told to think about.

Method

Generation is capacity × sun-hours × 365 × 0.85. Annual saving is generation × (40% × usage rate + 60% × feed-in rate). Payback is installed cost ÷ annual saving. Sun-hours are BOM climatology per suburb; tariffs are indicative state averages cross-checked against the AER Default Market Offer. Every figure derives from data published on our suburb pages, so any number here can be checked against a live page.

Limits

• Tariffs are indicative state averages, not quotes. Real rates vary by retailer, plan, network and meter type.
• Feed-in rates are deliberately conservative — the low end of each state's range, so savings are understated rather than overstated. WA's DEBS scheme pays 2–10c against the 3c modelled here.
• Sun-hours are scaled climatology, not measurement — capital-city BOM data scaled to each suburb's annual average.
• Payback excludes battery storage, EV charging, tariff inflation, panel degradation and movement in STC prices.
• Self-consumption is the largest single lever and it is a household behaviour, not a location.