Solar panel orientation myths in Perth: busted

Face north for the best solar generation in Perth. That's true, and it's usually where the advice stops, leaving homeowners assuming any other direction is a compromise not worth making.

It isn't. A north-east or north-west roof generates about 96% of what a due-north roof produces at the same tilt. East and west come in around 86%. Even a south-facing array still generates meaningful electricity. Roof pitch, tariff timing, and shading usually matter more to your bill than the last few degrees of azimuth.

This guide works through five common orientation myths and what the numbers actually show for Perth roofs.

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Do only north-facing panels work in Perth?

No. Panels facing other directions still generate significant electricity, and for plenty of roofs they're the only realistic option.

Here's the annual generation penalty for different orientations and tilts, compared with a north-facing roof at 25° tilt:

A north-east facing system at 25° tilt generates around 96% as much as a pure north system. An east-facing system at the same tilt generates around 86%. Real reductions, but nowhere near a reason to rule the orientation out.

If north isn't available, say the north side of the roof is taken up by a large dormer window, or the block is narrow with only east and west roof faces, east-facing panels are still worth installing. For the fundamentals of how each direction performs, see our guide to solar panel orientation in Perth.

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Are east and west panels equally bad?

No, not once you factor in when you use power. East and west generate close to the same amount over a year, but at different times of day, and that timing changes which one suits your household better.

East-facing panels:

• Generate more in the morning (7am–12pm)
• Suit households that use power heavily in the morning: washing, cooking breakfast, EV charging before work
• On Midday Saver, the super off-peak window starts at 9am, so east panels are already generating before it begins

West-facing panels:

• Generate more in the afternoon (12pm–5pm), peaking around 2–3pm
• More of their generation falls inside the Midday Saver super off-peak window (9am–3pm)
• Any surplus after 3pm exports at the DEBS peak rate (3pm–9pm, 10c/kWh)

Which tariff you're on changes the answer: On the A1 flat-rate tariff, east and west produce about the same annual value. On Midday Saver, west panels capture more of the super off-peak window, while east panels generate more before 9am, when the off-peak rate is 24.34c/kWh. For self-consumption, west tends to come out marginally ahead.

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Is an east-west split just a compromise for roofs with no north face?

Not necessarily. Splitting panels across east and west roof faces can outperform a pure north array for some households, even when north is technically available.

Why the timing matters: A north-facing array peaks around noon. For households that use most of their power in the morning and evening, a typical 9-to-5 pattern, a lot of that midday generation gets exported at low DEBS rates instead of being used at home.

An east-west split spreads generation across the morning and afternoon instead, with a flatter, lower midday peak. That can lift self-consumption for households with:

• Morning routines: school, work, appliance use
• Evening cooking and entertainment, when west panels are still catching the afternoon sun

Total generation: An east-west split typically generates around 86% of what a pure north system would generate from the same panel area, close to what a single east or west-facing array produces on its own.

When an east-west split makes sense:

• A long east-west ridgeline roof with good area on both sides
• A household with significant morning and late-afternoon consumption
• No battery planned in the near term (a battery smooths the generation shape regardless of orientation)

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Does roof pitch matter as much as orientation?

Not much, at Perth's latitude of about 32°S. Tilt angle has a far smaller effect on generation than which direction the roof faces.

Perth's optimal tilt for maximum annual generation is 30°. Away from that:

• Flat roof (5°): about 7% less than optimal
• Typical suburban roof (15–22°): about 2% less than optimal
• Moderate slope (25–30°): effectively optimal
• Steep roof (40°): about 1% less than optimal

The practical range of Perth suburban roofs, 12–30°, spans only around 3.5% in annual generation. That's not enough to base a decision on. Don't rule out a roof because the pitch is 15° instead of 25°.

For a deeper look at tilt angles and when paying for a tilt frame is worth it, see our guide to solar panel tilt in Perth.

Winter vs summer tilt trade-off: A steeper tilt (30°+) catches more winter sun, since the sun sits lower in the sky. A shallower tilt (10–15°) catches more summer sun. Because Perth generates more overall in summer, a flatter tilt is often marginally better for total annual energy, though the difference is small across standard roof pitches.

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Should every panel just face north for the best return?

Not always. For households with high self-consumption, splitting orientation can improve the financial return even when it lowers total generation.

A 6.6kW system facing north generates around 28kWh on an average day across the year (more in summer, less in winter), peaking between 10am and 2pm. If most of a household's consumption happens in the morning and evening, a meaningful share of that midday peak, roughly 10–15kWh, exports at the DEBS off-peak rate of 2c/kWh instead of being used.

A split system, say 4kW north and 2.5kW east, spreads generation wider across the morning. The east panels start generating from around 7am. That earlier generation lines up better with breakfast, hot water, washing, and the school run, lifting the self-consumption percentage.

The financial comparison:

• Pure north 6.6kW: more total energy generated, but more of it exports at 2c/kWh
• Split 4kW north + 2.5kW east: slightly less total generation, but a higher self-consumption rate

For a household on Midday Saver without a battery, that self-consumption difference matters a lot: it's the gap between displacing the 55.33c/kWh peak rate and exporting at 2c/kWh. A split array can produce a better financial return even with lower total generation.

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What matters most for solar returns in Perth?

1. Shading, the biggest factor: even partial shade during peak hours meaningfully cuts output, and it's a bigger swing than orientation choice. Deal with shade before you optimise orientation. For a closer look at how much shade actually costs you, see how shading affects solar output in Perth.

2. Tariff choice: moving from A1 to Midday Saver changes which generation hours are worth the most, which affects the best system design for your home.

3. System size: for most Perth households, a bigger system in a non-optimal orientation beats a smaller system in an optimal one.

4. Battery or no battery: with a battery, orientation shape matters less, since it stores the midday peak for evening use regardless. Without one, matching generation to your consumption pattern matters more.

5. Orientation, less important than most people assume: north is best, but north-east and north-west are only marginally worse. East and west come with a real penalty but are still worth installing.

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Use the BillWise solar calculator to model different orientation scenarios against your own consumption profile. The best orientation for your household might not be the one that maximises total annual generation. For the full picture on getting solar right in Perth, start with our complete Perth solar guide.