Solar Panel Orientation Calculator (Australia)

How to use this calculator

Enter three numbers:

1. Your latitude — right-click any Australian location on Google Maps. Latitudes are negative for the Southern Hemisphere — enter as a positive number. Sydney 33.9, Melbourne 37.8, Brisbane 27.5, Perth 31.9, Adelaide 34.9, Hobart 42.9, Darwin 12.5.
2. Panel azimuth — the compass direction your roof face points, in degrees clockwise from true north (0° = north, 90° = east, 180° = south, 270° = west). Use the compass quick-pick buttons if you do not have a precise reading.
3. Panel tilt — the roof pitch from horizontal. A flat roof is 0°, a typical Australian pitched roof is 22°–25° (a 1980s brick-veneer is usually 22.5°).

The calculator returns the production factor — the percentage of optimal yield you will capture — alongside the optimal orientation for your latitude and a verdict on whether the array is worth installing as-is.

How orientation affects Australian solar output

Solar panels generate the most output when sunlight strikes the surface perpendicular. Two angles control how often that happens:

• Azimuth (compass direction) determines whether the sun is in front of, beside or behind the panel during the day. North-facing arrays in Australia capture the daily solar arc symmetrically.
• Tilt (angle from horizontal) determines whether the sun hits the panel head-on or at a glancing angle. The right tilt depends on your latitude — see the solar panel tilt calculator for the optimal value.

Get both right and a Sydney 6.6 kW array produces about 9,200 kWh per year. Get one wrong and you lose 5%–25%. Get both wrong and the loss can stretch to 40%–55%.

How much each orientation produces in Australia

The table below shows approximate annual production factor relative to optimum for typical Australian latitudes (12°–43°S). Values are derived from Bureau of Meteorology irradiance data and Clean Energy Council reference yield modelling, rounded to the nearest 5%.

Three things to notice:

1. Flat panels lose the same regardless of compass direction. All orientations sit at 90% of an optimally-tilted north array — useful to know for ballasted commercial flat-roof installs in Sydney CBD or Melbourne Docklands.
2. East and west are nearly identical in total output, but their value differs significantly under time-of-use tariffs. Ask your installer to model your specific retailer plan.
3. South-facing roofs in Australia are rarely worthwhile. A 22° south-facing array produces only 65% of an equivalent north-facing one. Most CEC-accredited installers will recommend either an east-west split or moving the array to a shed or carport rather than installing on a single south slope.

The formula behind this calculator

The production factor uses a first-order approximation of projected solar irradiance integrated over a typical year:

factor = cos(Δβ) × (1 − 0.3 × (1 − cos(Δγ)))

Where:

• Δβ = (panel tilt) − (optimal tilt). Optimal tilt is approximated as latitude × 0.76, weighting the long Australian summer over the mild winter. This is the same rule used in the solar panel tilt calculator.
• Δγ = the angular distance between panel azimuth and equator-facing azimuth (0° in the Southern Hemisphere). Wrapped so values stay in the 0°–180° range.
• The 0.3 coefficient in the azimuth term is fitted against PVWatts and SunWiz output and accounts for typical Australian diffuse-light fractions. Pure cosine over-penalises east/west under partly-cloudy summer skies.

Limits of the model. It is a back-of-envelope estimator, not an hour-by-hour simulator. It assumes:

• Typical Australian climate with diffuse irradiation fraction of 25%–35%
• Standard fixed-rack mounting (not single- or dual-axis tracking)
• Tilts ≤ 45° and azimuth deviations ≤ 135°

For unusual roofs, complex shading, or commercial installations above 30 kW, run a free PV-GIS or paid Pvsyst hour-by-hour simulation.

When to install at sub-optimal orientation anyway

Solar production is one factor; cost is the other. A north-facing ground mount might be optimal but cost AUD 6,000 more than tying into your existing east-facing roof. The CEC-installer rule of thumb:

• Above 90% of optimal: install as-is. The 5%–10% loss is dwarfed by the cost of re-orienting.
• 75%–90% of optimal: install if the roof is the only sensible option, but oversize the array by 15%–25% to compensate. Verify expected output with your installer’s CEC-compliant performance estimate.
• Below 75% of optimal: consider an alternative — an east-west split (often the best fix for south-facing-only roofs by re-using the front and back slopes), a shed roof, or a ground-mount on rural blocks. Payback at typical AU feed-in tariffs of 4c–8c/kWh stretches uncomfortably long below this threshold.

For full system economics, use the solar panel charge time calculator for off-grid setups, or check the SunWiz STC calculator for grid-tied figures and rebate eligibility.

Common Australian orientation mistakes

• Reading roof azimuth from a magnetic compass without correction. Australian declination ranges from 5° east in Perth to 15° east in Brisbane. Use the Geoscience Australia AGRF calculator for an accurate true bearing.
• Confusing roof pitch with tilt. Australian roofers usually quote pitch in degrees (15°, 22.5°, 30°) but pre-1980s plans sometimes use rise:run. A 4:12 American-style pitch is 18.4° tilt.
• Ignoring shading from gum trees, neighbouring two-storey extensions and air-conditioning units. A perfectly oriented array under a deciduous tree will under-perform a poorly oriented array in full sun. Use Sun Surveyor or the SolarEdge Designer free shading tool.
• Mixing east-facing and west-facing strings on a single string inverter. String inverters lose more yield than the calculator predicts when panels in the same string face different directions. Use micro-inverters (Enphase) or DC optimisers (SolarEdge, Tigo) for east-west splits — the AUD 800–AUD 1,500 premium pays back through the recovered yield within 5–7 years.

What the Clean Energy Council says

The CEC Design Guidelines for Grid-connect Solar PV define acceptable orientations in their performance modelling annex. For STC eligibility, the design must be installed by a CEC-accredited installer and the system performance estimate must use either PV-GIS, PVWatts, SunWiz or Pvsyst. CEC’s reference orientation factors broadly match the table above and are updated annually.

The Australian Energy Regulator (AER) publishes current feed-in tariff rates by retailer — check rates before deciding between east, west or split orientations, because the value of generation outside 9am–4pm depends entirely on your tariff structure.

Related Australian solar calculators

• Solar panel tilt calculator — optimal pitch by Australian latitude
• Solar panel charge time calculator — off-grid battery sizing
• Solar panel voltage calculator — AS/NZS 3000 voltage drop
• Solar panel wire size calculator — DC and AC cable sizing per AS/NZS 5033

For installation, always use a CEC-accredited designer and installer. CEC accreditation is required to claim Small-scale Technology Certificates (STCs) and to access most state rebates including the Solar Homes Program (VIC), Solar for Low-Income Households (NSW) and Home Battery Scheme (SA).