Your roof, your number
Why the address: a north-facing roof and a south-facing one differ by a quarter to a third in annual output, and that moves a 10-year payback to 13 or more. Give us the street number, street, suburb, state and postcode and we read your actual roof from aerial imagery: each face's pitch, direction and shade, how many panels fit, the size that suits, its October 2026 index price for the nearest indexed city, and what it makes and saves on that roof. The address is used once to find the roof and is not kept.
How the number is made
The address goes to the Google Geocoding API for a point, and that point to the Google Solar API, which returns the building's roof from aerial or satellite imagery: each face with its pitch, compass direction, area and annual sunshine (shade included), the number of panels that fit, and the annual DC energy of each panel position and of each panel count. Google sizes in its 250 W reference panel; the page converts to 440 W panels by area, derates DC to AC at 0.85 (Google's own default) and takes the per-kW yield of the best positions for each size on the site's ladder (3, 5, 6.6, 8, 10, 13, 20 kW).
The price for each size that fits is the October 2026 Solar Choice standard and premium installer offer for the nearest indexed city, after STCs at $39 per certificate for the postcode's zone, exactly as on the city and postcode pages. Saving and payback use the state's usage rate and feed-in median with 35 per cent of output used at home, the same model as the worth-it pages. "Your number" is the largest ladder size that fits under 10 kW, the common single-phase inverter ceiling. Imagery quality is shown with each result: HIGH is 0.1 m aerial, MEDIUM 0.25 m aerial, BASE 0.25 m satellite; a BASE reading can mis-draw a face.
Nothing about the address is kept. The geocode is cached under a one-way hash of the address and the roof reading under its rounded coordinates, both for 90 days, so a second lookup of the same house costs nothing; lookups are limited to twenty an hour per connection. See the privacy policy.
What direction does to output
The roof reading above already prices your actual faces. For the general picture: on a 20-degree roof, due north gives at least 99 per cent of the best possible annual output in every capital except Darwin, and an east or west face gives at least 85 per cent in Adelaide, Brisbane, Canberra and Darwin, with Melbourne just under. The worst direction, close to due south, still produces two thirds to four fifths of the best:
| Capital | Worst direction | Output vs best |
|---|---|---|
| Adelaide | 184° | 74% |
| Brisbane | 177° | 71% |
| Canberra | 178° | 72% |
| Darwin | 199° | 83% |
| Hobart | 193° | 66% |
| Melbourne | 186° | 71% |
| Perth | 194° | 73% |
| Sydney | 187° | 72% |
Source: SolarQuotes, Solar panel direction (PVWatts), April 2019, updated March 2025. The author notes the insolation data has moved since, so treat the shares as a guide; the per-roof figures above come from current imagery.
The bands and yields behind the result, October 2026
| City | Zone | 6.6 kW standard | 6.6 kW premium | 10 kW standard | 10 kW premium | Average yield |
|---|---|---|---|---|---|---|
| Sydney | Zone 3 | $6,170 | $7,284 | $8,780 | $10,490 | 1424 |
| Melbourne | Zone 4 | $6,218 | $7,234 | $8,920 | $10,410 | 1314 |
| Brisbane | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1533 |
| Perth | Zone 3 | $5,294 | $6,522 | $8,240 | $9,880 | 1606 |
| Adelaide | Zone 3 | $5,812 | $7,126 | $8,360 | $10,010 | 1533 |
| Canberra | Zone 3 | $6,144 | $7,310 | $8,340 | $10,100 | 1570 |
| Hobart | Zone 4 | $7,544 | $8,886 | $11,460 | $13,240 | 1278 |
| Darwin | Zone 2 | $10,250 | $12,260 | $14,930 | $18,250 | 1606 |
| Gold Coast | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1548 |
| Sunshine Coast | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1571 |
| Newcastle | Zone 3 | $6,170 | $7,284 | $8,780 | $10,490 | 1488 |
| Wollongong | Zone 3 | $6,170 | $7,284 | $8,780 | $10,490 | 1356 |
| Geelong | Zone 4 | $6,218 | $7,234 | $8,920 | $10,410 | 1297 |
| Central Coast | Zone 3 | $6,170 | $7,284 | $8,780 | $10,490 | 1394 |
| Townsville | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1634 |
| Cairns | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1533 |
| Toowoomba | Zone 3 | $6,756 | $8,020 | $9,460 | $11,210 | 1591 |
| Launceston | Zone 4 | $7,544 | $8,886 | $11,460 | $13,240 | 1438 |
| Ballarat | Zone 3 | $6,218 | $7,234 | $8,920 | $10,410 | 1360 |
| Bendigo | Zone 3 | $6,218 | $7,234 | $8,920 | $10,410 | 1477 |
Source: Solar Choice Price Index, October 2026, standard and premium installer offers after STCs. Basis of each figure: 3, 5 and 10 kW cells are published by Solar Choice; 6.6 kW and 8 kW are interpolated and 13 kW and 20 kW scaled by Solar Scorecard at the same dollars per watt (derived); cities Solar Choice does not index use the nearest indexed capital. Where our own quotes series holds ten or more checks for a city and size, that cell is replaced by the quotes median and marked with its count.
Roof and size questions
How many solar panels fit on a typical Australian roof?
20 to 30 panels of 440 W, about 9 to 13 kW, fit on a typical detached roof of 150 to 200 square metres once hips, valleys, vents and the poorest face are left out; a smaller roof or one with a flue and a skylight on the north face may take 12 to 15, about 6.6 kW. The reading above counts your roof from imagery rather than a rule of thumb.
Does a south-facing roof work for solar in Australia?
A south-facing 20-degree roof produces about 66 to 83 per cent of what the best direction gives, Hobart at the low end and Darwin at the top, on PVWatts figures for the capitals. It works, with a longer payback; an east-west split usually beats forcing panels onto the south face.
Which solar system size should I choose?
6.6 kW suits a household using 15 to 20 kWh a day and has been the common install; a 10 kW system with a 10 kW inverter is the usual single-phase ceiling and suits a larger house or a future battery or electric car. The table above prices every size that fits your roof; the October 2026 index puts 6.6 kW at $6,218 to $7,234 in Melbourne and $6,170 to $7,284 in Sydney after STCs.
What if my address has no roof data?
Google covers most Australian cities and large towns at 0.1 to 0.25 m resolution, and more of the country from satellite imagery, but not every building; a new house or a rural address may return nothing, and a unit block returns the whole building. The postcode and city pages carry the price bands either way.
Is my address stored?
No. The address is used once to find the roof and is not written anywhere; the roof reading is cached against its rounded coordinates for 90 days so a repeat lookup is free, and lookups are limited to twenty an hour per connection.