Solar panel orientation myths for Perth — busted
Perth homeowners receive a lot of advice about solar orientation that ranges from oversimplified to wrong. North is best — but how much worse is east, west, or north-east? What about split arrays? Here's what the numbers actually show.

The most common advice Perth homeowners receive about solar orientation is "face north for best results." This is true. But the full picture is more nuanced — and understanding it can save you from making orientation decisions based on oversimplified rules.
Myth 1: "Only north-facing panels are worth installing"
Reality: Solar panels at other orientations still generate significant electricity.
Generation penalty compared to optimal north-facing, 25° tilt in Perth:
| Orientation | Tilt | Approximate annual generation penalty | |---|---|---| | North | 25° | 0% (reference) | | North-east | 25° | -6% to -10% | | North-west | 25° | -6% to -10% | | East | 25° | -17% to -23% | | West | 25° | -17% to -23% | | South | 25° | -35% to -45% | | North | Flat (5°) | -5% to -8% | | North | Steep (40°) | -5% to -10% |
A north-east facing system at 25° generates approximately 90–94% as much as a pure north system. An east-facing system at 25° generates approximately 77–83%. These are real reductions — but not zero.
For a household where east is the only available orientation (north roof occupied by a large dormer window, or a narrow block with only east-west roof orientation), installing east-facing panels is still worthwhile.
Myth 2: "East and west panels are equally bad"
Reality: For self-consumption optimisation, east and west have different timing characteristics that matter depending on your consumption profile.
East-facing panels:
- Generate more in the morning (7am–12pm)
- Better for households that consume heavily in the morning (washing, cooking breakfast, EV charging before work)
- On Midday Saver, the super off-peak window starts at 9am — east panels are already generating before this
West-facing panels:
- Generate more in the afternoon (12pm–5pm, peaking around 2–3pm)
- More generation falls within the Midday Saver super off-peak window (9am–3pm)
- Export to DEBS peak (3pm–9pm, 10c/kWh) for any surplus after 3pm
For different tariff situations: On A1 tariff (single flat rate), east and west produce approximately the same annual value. On Midday Saver, west panels capture more of the super off-peak window (9am–3pm), while east panels generate more before 9am (at off-peak 24.34c/kWh). For self-consumption, west may be marginally better.
Myth 3: "Split east-west arrays are a compromise for properties with no north roof"
Reality: An east-west split can outperform a pure north array in certain situations.
The morning and afternoon coverage advantage: A north-facing array peaks at noon. For households consuming morning and evening electricity (typical 9-to-5 household), significant midday generation is exported at low DEBS rates.
An east-west split generates a flatter production curve — more generation in morning and afternoon, less peak midday generation. This can increase self-consumption percentage for households with:
- Morning school/work routines with appliance use
- Evening cooking and entertainment when west panels catch afternoon sun
Total generation: An east-west split typically generates 85–92% of what a pure north system would generate from the same total panel area.
When east-west makes sense:
- Long ridgeline east-west oriented roof with good area on both sides
- Household with significant morning and late-afternoon consumption
- Battery not planned immediately (battery smooths the peak generation shape regardless)
Myth 4: "The exact roof pitch matters a lot"
Reality: In Perth's latitude (-31.9°), tilt angle has a much smaller impact than orientation.
Perth's optimal tilt for maximum annual generation is approximately 25–30° (roughly matching latitude). But:
- Flat roof (5°): approximately 5–8% less than optimal
- Typical suburban roof (15–22°): approximately 1–4% less than optimal
- Moderate slope (25–30°): approximately optimal
- Steep roof (40°): approximately 4–8% less than optimal
The practical range of Perth suburban roofs (12°–30°) spans approximately 5% in annual generation. This is not a meaningful difference for most system decisions — don't reject a roof orientation because the pitch is 15° instead of 25°.
Winter vs summer tilt trade-off: A steeper tilt (30°+) captures more winter sunlight (sun lower in the sky); a shallower tilt (10–15°) captures more summer sunlight. Perth's higher annual generation in summer means a flatter tilt is often marginally better for total annual energy, but the difference is small for standard roof pitches.
Myth 5: "Install all panels north for maximum return"
Reality: For high self-consumption, diversifying orientation can improve financial returns.
If a 6.6kW system faces north, it generates approximately 25–30kWh on a Perth summer day, peaking between 10am and 2pm. If most household consumption happens in the morning and evening, 10–15kWh of this midday peak exports at 2c/kWh DEBS off-peak.
A split system — say, 4kW north and 2.5kW east — generates a wider spread of generation through the morning. The east panels generate from 7am–12pm. The morning generation aligns better with breakfast, hot water, washing, and school routine loads — increasing self-consumption percentage.
The financial comparison:
- Pure north 6.6kW: generates more total energy, but more exports at 2c/kWh
- Split 4kW north + 2.5kW east: generates slightly less total, but self-consumption rate is higher
For households on Midday Saver without battery storage, the self-consumption difference matters significantly (displacing 55.33c/kWh peak vs exporting at 2c/kWh). A split array can have better financial returns even though its total generation is lower.
What actually matters most for Perth solar returns
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Shading (highest impact): even partial shade during peak hours can reduce output by 20–50%. Avoid shade first, then optimise orientation.
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Tariff choice: switching from A1 to Midday Saver changes which generation hours are most valuable. This affects optimal system design.
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System size: for most Perth households, a larger system in a non-optimal orientation outperforms a smaller system in an optimal orientation.
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Battery vs no battery: with a battery, the orientation shape matters less (battery stores midday peak for evening use regardless). Without a battery, self-consumption alignment with generation profile matters more.
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Orientation (less impact than most assume): north is best, but north-east and north-west are only marginally worse. East and west have meaningful penalties but are still viable.
Use the BillWise solar calculator to model different orientation scenarios against your actual consumption profile — the optimal orientation for your household may differ from the orientation that maximises total annual generation.
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