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The direction and angle of your panels significantly affects how much energy you generate, and when you generate it. Here's what Perth homeowners need to know.
Optimal for maximum annual output
In the southern hemisphere, the sun tracks across the northern sky. North-facing panels face the sun throughout the day and generate the most energy year-round. This is the default recommendation for Perth homes on a flat-rate tariff.
Strong afternoon and peak-period output
West-facing panels give up about 13% of annual output versus north-facing, but concentrate generation in the 2–5 pm window, aligning with the Synergy peak rate period (3–9 pm). If your household uses significant power in the afternoon (e.g. air conditioning), or you're on a TOU tariff, west-facing can improve self-consumption and offset expensive peak-period grid draws.
Morning generation, useful for early risers
East-facing panels produce well in the morning, which suits households with early morning consumption peaks (pool pumps, air conditioning, breakfast appliances). Annual output is similar to west-facing. An east + west split (no north face available) is a common solution for homes with a ridge running north-south.
Not recommended for WA
South-facing panels never face the sun directly at Perth's latitude, so annual output falls to about 72% of an optimally tilted north-facing array. Avoid unless no other option exists. If it is your only roof face, keep the array as close to flat as the structure allows: the modelled best tilt for a south face is 0°, and steepening it lowers output rather than lifting it.
Most Perth homes have existing roof pitches of 10–25°. A 30° tilt is optimal for the Perth latitude, but the gain over a typical 15° roof is only about 2% of annual output. Rack-mounting to increase tilt adds cost and may need council approval depending on height.
| Tilt angle | Relative output |
|---|---|
| 0° (flat) | 90% |
| 10–15° | 97% |
| 28–32° | 100% |
| 35–40° | 99% |
| 45°+ | 98% |
Output relative to optimal north-facing, 30° tilt in Perth, modelled by the shared WattMate orientation and tilt model. Actual performance depends on shading, soiling, and inverter configuration.
Yes. East- and west-facing roofs at typical Perth pitches still produce about 87% of the annual output of a north-facing system. The financial return is slightly lower but still strong. Your installer will model the exact output using tools like PVsyst or PVWatts before quoting.
An east + west split or north + west split can increase self-consumption compared to a single north-facing array, especially if you have peak demand in both morning and evening. The total output won't exceed a fully north-facing equivalent, but the profile can reduce grid draw at the ends of the day.
Yes, shading is often the bigger factor in WA. A north-facing panel that's shaded by a neighbour's tree in summer afternoons may produce less than an unshaded west-facing one. Ask your installer to run a shading analysis (PVsyst shade scene or on-site assessment) before finalising placement.
Yes, but self-cleaning by rain is reduced and dust accumulation is faster. Flat mounting is common on commercial buildings. For residential homes, a modest tilt (even 10°) improves cleaning and output. If your roof pitch is very low, panel tilt frames can angle them up. Ask your installer if the cost is justified for your site.
Perth sits at 31.9° south latitude. The theoretical optimal tilt for maximum annual output is close to your latitude: 28–32° is well matched. Perth receives 5 peak sun hours per day on average (BOM), which is among Australia's best regardless of tilt, because the direct normal irradiance is so high.
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