West-facing solar in Perth: when it's the right choice

North-facing solar panels produce the most total energy over the year in Perth. But total energy isn't always what matters most — it's the value of that energy that determines your payback. West-facing panels produce 10–15% less total energy than north-facing, but they generate more of it in the afternoon and evening when Perth's Midday Saver peak rates apply.

Generation profile by orientation

Perth sits at approximately 32° south latitude. At this latitude:

North-facing panels (best total generation):

• Peak generation: solar noon (12pm–1pm)
• Generation curve: symmetric, peaks at midday, drops off evenly toward morning and evening
• Annual yield: ~1,600–1,800 kWh/kW (Perth baseline)

West-facing panels:

• Peak generation: 2pm–4pm
• Generation curve: slower ramp in morning, peaks in afternoon, output continues until sunset
• Annual yield: approximately 1,380–1,530 kWh/kW (about 85–87% of north-facing)

East-facing panels:

• Peak generation: 9am–11am
• Annual yield: similar to west-facing (~85% of north)

Loss in percentage terms:

• North → West: 10–15% fewer kWh/year
• North → East: 10–15% fewer kWh/year
• North → South: 30–40% fewer kWh/year (significant penalty, avoid unless unavoidable)

When west-facing is the better financial choice

On Midday Saver tariff

Perth's Midday Saver tariff creates a dramatic time-of-use pricing structure:

• 9am–3pm (super off-peak): 8.85c/kWh
• 3pm–9pm (peak): 55.33c/kWh

The impact on north-facing panels: Solar generation peaks at noon — which is within the super off-peak window. If you're on Midday Saver and already have a battery that fills up by midday, excess north-facing generation exports at just 2c/kWh (DEBS off-peak).

The advantage of west-facing on Midday Saver: West-facing panels shift generation into the 2pm–6pm window. A 6kW west-facing array in Perth generates approximately 3–4 kW from 3pm–5pm on a clear summer day — directly within the peak window where:

1. Self-consumed generation replaces 55.33c/kWh grid electricity
2. If a battery is full and exports, DEBS peak (10c/kWh) applies

For a household already consuming energy during peak hours (after-work AC, cooking, pool pump), west-facing panels directly reduce the most expensive electricity of the day.

Export limit constrained households

Synergy and Western Power impose export limits in many suburbs — commonly 5kW inverter-level or lower in constrained areas. If your system is export-capped, you don't benefit from excess solar being exported anyway. West-facing panels time the generation closer to when the household is consuming — maximising self-consumption rather than wasted export.

Households with EVs charging in the afternoon

EV owners who plug in after work (5pm–7pm) benefit disproportionately from west-facing solar. A west-facing array in Perth can still generate 1–2 kW at 5pm in summer, providing meaningful contribution to EV charging. North-facing panels are generating near-zero at this time.

When the roof forces the choice

Many Perth homes, particularly older stock with hip roofs, don't have large north-facing sections available. West-facing panels on a good roof face are substantially better than north-facing panels on a shadowed or partially obstructed face.

When north-facing is clearly better

• Without Midday Saver tariff: on standard A1 (33.26c flat rate), every kilowatt-hour is worth the same regardless of time. More total kWh = more savings = north wins.
• Battery-less household: without a battery to absorb the noon surplus, north-facing generation may export at 2c/kWh during super off-peak. Still better than west, but the gap narrows.
• High daytime load (home office, shift workers): if your household consumes heavily from 9am–3pm, north-facing panels directly displace that consumption.

The east-west split approach

For homes where a single north-facing section is insufficient for the desired system size, an east-west split is often better than mixing north with south:

East-west split benefits:

• Broader generation window: starts generating 2–3 hours earlier (east) and continues 2–3 hours later (west) than a pure north configuration
• Avoids midday export peak entirely — generation ramps up and trails off on each side rather than spiking at noon
• Works well with or without a battery

East-west split typical configuration:

• 3.3kW east / 3.3kW west (or asymmetrically weighted toward west for Midday Saver households)
• May require a dual-MPPT inverter or two separate inverters to optimise each face independently
• Total generation: approximately 85% of equivalent north-only capacity, but with a flatter, more useful daily profile

Practical recommendation

On Midday Saver with a battery: West-only or east-west split can outperform north-only in financial terms, because you're shifting value to peak hours. The 10–15% generation loss is recovered by the rate differential.

On standard A1 tariff: North-facing remains the best orientation. Install as much north-facing as your roof allows before considering other orientations.

Constrained roof with limited north: East-west split beats a partial north + south combination. Never install south-facing panels unless you've exhausted all other options.

Annual generation estimates based on 5.0 peak sun hours average, Perth location (32°S). Actual generation varies by roof pitch, shading, and panel specification.