Solar panel orientation in Perth: does your roof direction matter?

North-facing at around 30° pitch is the best roof orientation for solar in Perth, but the penalty for other directions is smaller than most people assume. East or west-facing panels generate roughly 85–90% of what a north-facing system produces annually, southeast or southwest sit around 80%, and only true south-facing takes a real hit, down near 72% of north.

Most Perth homes don't have enough clear north-facing roof for a full system, so installers often propose east/west splits or use whatever face is available. Here's what you actually lose, and gain, with each option.

Why does roof orientation affect solar generation?

Perth is at approximately 32°S latitude. The sun rises in the east, arcs across the northern sky, and sets in the west. At solar noon, around midday, the sun is directly north and at its highest point. WA doesn't observe daylight saving, so that timing stays roughly the same year-round.

Panels facing north capture the most direct sun for the most hours per day, which is why north-facing generation is highest.

Panels facing east capture the morning sun well but miss the afternoon peak. West-facing panels do the opposite. South-facing panels receive minimal direct sun in winter and indirect summer sun only.

For more on how these numbers get twisted in sales conversations, our solar orientation myths guide works through the claims installers make about "north or nothing".

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How much generation do you lose with each orientation?

Annual generation as a percentage of north-facing output:

These are annual averages for Perth (32°S). The gap between north and east/west is larger in winter, when the sun is lower in the sky and spends more time in the northern arc, than in summer.

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Does roof pitch (tilt angle) matter for generation?

Perth's optimal fixed tilt for annual generation is approximately 28–32°, close to the latitude angle. Most residential roofs are built at 15–25°, which still performs well.

Generation impact of pitch:

For most Perth homes, roof pitch is a minor factor: the 15–25° range common in Perth residential construction captures roughly 97–99% of optimal. For a closer look at how much tilt actually moves the needle and when a tilt frame is worth the money, see our solar panel tilt guide and our breakdown of tilt frame costs. Flat roofs (commercial or some modern homes) can use ballasted mounts to achieve a better tilt, though this adds cost, covered in our flat roof solar guide.

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When does an east/west split make more sense than north-only?

Rather than putting all panels north, some homes split panels across east and west faces (or use east and north, or west and north).

Why an east/west split might make sense:

• Better morning/evening coverage. An east-facing panel generates strongly in the morning, useful for households that run appliances in the morning. A west-facing panel generates in the afternoon and into the evening, useful for later daytime loads, and better for Midday Saver households who want to delay peak-rate exposure.

• More panels fitted. If the north face is small, splitting across east and west allows a larger total system (more kWp) even if the per-panel yield is slightly lower.

• Export limiting compensation. For homes on the standard 1.5kW export limit, which is the fallback for systems without a stable internet connection or remote-disconnect capability rather than something set by suburb, a pure north-facing system generates a sharp midday peak that's largely curtailed. An east/west split spreads generation over more hours, reducing the fraction that hits the export cap at once.

Annual generation comparison, using a Perth baseline of roughly 1,500 kWh per kW per year for an optimally-oriented system:

• Pure north (6.6kW): ~9,900 kWh/year
• East/west split (3.3kW east + 3.3kW west): ~8,600 kWh/year (around 13% less than pure north)
• East/west split with a larger system (4kW east + 4kW west = 8kW): ~10,400 kWh/year, ahead of the 6.6kW north total

If the trade-off is "6.6kW all-north vs 8kW east/west split," the larger split can out-generate the smaller north system over a year. The east/west split wins on generation timing regardless.

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What actually matters for orientation, and what doesn't?

Matters:

• A south-facing roof as your primary installation area: a real generation loss, around 28% less than north. Avoid it unless you have no alternative.
• Partial shading during 10am–2pm peak hours from trees, chimneys, or neighbouring structures can be worse than orientation. A shaded north-facing panel may produce less than an unshaded west-facing one. Our solar shade analysis guide covers how to assess this before you sign a contract.

Doesn't matter much:

• The difference between pure north and NE or NW: around 4% annual generation, worth optimising but not a dealbreaker.
• Roof pitch in the 15–30° range: within 5% of optimal for Perth.
• Exact compass north versus slightly east-of-north: Perth solar tools (OpenSolar, PVsell) model this precisely, and installers should provide orientation-adjusted generation estimates.

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What should you ask your installer about orientation?

1. What orientation and tilt are the panels being installed at?
2. Can you show me the PVsell or OpenSolar model with the specific orientation and shading inputs for my address?
3. If my north face is limited, are there east/west options that achieve similar annual kWh?
4. Is there any shading from trees, vents, or neighbouring structures that will affect the modelled panels?

A reputable installer should provide a generation estimate (kWh/year) based on your actual roof orientation, not just a generic "6.6kW system = 9,900 kWh" figure. If a quote doesn't include orientation-adjusted generation estimates, ask for them.

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Generation percentages and kWh figures are based on Perth solar modelling at approximately 32°S latitude, using a typical peak-sun-hour average with normal system losses applied. Actual output depends on your specific roof pitch, azimuth, and local shading.