South-Facing vs East/West: How Orientation Affects Solar Output

Ask any solar installer their golden rule and they'll say: south-facing is best.

But what if your roof faces east? Or south-west? And by how much does orientation really matter? Can you still get a decent return from east-west facing panels?

This article breaks down the real impact of aspect angle on solar output, using PVGIS data for the UK. We'll compare south vs east/west in terms of generation, savings, and payback—so you know what to expect if your property isn't perfectly south-facing.

The Solar Fundamentals: Why South Is Best

In the UK, the sun's path traces from east (sunrise) to south (midday) to west (sunset). Panels facing south intercept the sun's strongest rays at noon, when irradiance is highest.

Panels facing east catch strong morning sun; west catch strong evening sun. But the sun is lower and weaker at these times, so total daily energy is less.

Panels facing north receive almost no direct sun (only diffuse sky light) and are essentially unusable for plug-in solar.

Real Output Data: South vs East/West

Using PVGIS data for London, here's annual generation for an 800W system in different orientations, tilted at 25°:

Key insight: South-east or south-west (±45° from due south) loses only ~5–7% output. East or west (±90° from south) loses ~25%. North-east or north-west loses ~40%.

The difference is real but manageable. East/west is viable; north is not.

Why South-East and South-West Are Nearly As Good

South-east and south-west capture the sun's strong morning (east) and afternoon (west) rays, respectively. The midday sun isn't quite as direct, but the overall daily energy is almost the same as south-facing.

Summer example (London, June):

• South-facing: 115 kWh/month
• South-east facing: 110 kWh/month (-4%)
• East-facing: 80 kWh/month (-30%)

The steeper the angle away from south, the more output suffers—but the relationship is non-linear. The first 45° deviation (south → south-east) costs almost nothing. The next 45° (south-east → east) costs a lot more.

East vs West: Which Is Better?

East and west are nearly identical in annual output (~75% of south). But they differ slightly in seasonal profile:

East-Facing:

• Strong morning generation (6am–12pm)
• Weakens in afternoon
• Good for homes with morning usage (e.g. large breakfast, laundry in the morning)
• Better in spring/autumn when mornings are cool and sunny

West-Facing:

• Weak morning generation
• Strong afternoon generation (12pm–6pm)
• Good for homes with afternoon usage (e.g. work from home, evening meal cooking)
• More vulnerable to afternoon cloud (Atlantic systems often arrive in afternoon)

For self-consumption: East is marginally better (less afternoon cloud risk). For Time-of-Use tariffs, it depends on your peak-rate window. Most ToU tariffs peak 4–9pm, so west's afternoon generation is more valuable.

For export: Both are equally bad (~0p under standard tariffs). If you have an export tariff (Octopus Flux, etc.), east's reliability matters more than west's intensity.

Verdict: East and west are practically equivalent, ~5–10% preference for east if you self-consume.

Real Payback Impact: How Orientation Shifts Timeline

Here's the critical number: How does orientation affect payback?

Assuming an 800W system, £800 cost, and 30p/kWh tariff in London:

East or West costs you 1.1 years (13 months) of payback compared to south.

• South: profitable after 3.1 years
• East/West: profitable after 4.2 years
• Over a 25-year panel lifetime, east/west still generates ~£3,500 net profit. Still worth doing, but with longer patience.

When East/West Is Actually Viable

East/west facing panels make sense if:

1. You have no south-facing option – your property's layout means south is impossible. East/west is the only choice.
2. You work from home with afternoon usage – west-facing panels generate when you're using the most power. This tightens payback by improving self-consumption.
3. You have a Time-of-Use tariff peaking in afternoon/evening – Octopus Flux's 4–9pm peak window aligns with afternoon west generation, boosting value.
4. You have a south-east or south-west option instead – this loses only ~5%, so go for it. Only east or west (full 90°) is notably constrained.

When East/West Is NOT Viable

East/west facing panels become marginal if:

1. System cost is high – above £1.20/W. The longer payback (4.2 years) needs cheap panels to pencil out.
2. You work away from home all day – most generation goes to export at 0p. Without a good tariff, return is poor.
3. You're in Scotland or the North – generation is already lower. East/west loses 25%, so total output is very low. Payback exceeds 5 years, making it marginal.
4. You have no battery and a standard tariff – combine low output + zero export reward = poor economics. Switch to a ToU tariff or battery first.

How the Calculator Models Orientation

Our savings calculator lets you choose aspect:

• South – 0° (best)
• South-East or South-West – ±45° (excellent)
• East or West – ±90° (acceptable)

It queries PVGIS for your exact postcode and orientation, so the estimate accounts for your region's cloud patterns and sun geometry.

Pro tip: If you have a south-west facing roof, always run two calculations:

1. With "South" to see the theoretical best-case
2. With "South-West" to see the realistic expectation

The difference usually ~3–5% for south-west.

Seasonal Variation: Does Orientation Matter More in Winter?

This is a subtle point: east and west lose more output in winter, when the sun is already low and weak.

January generation (London):

• South-facing: 45 kWh
• East-facing: 28 kWh (38% lower)
• West-facing: 25 kWh (44% lower)

June generation:

• South-facing: 115 kWh
• East-facing: 95 kWh (17% lower)
• West-facing: 100 kWh (13% lower)

East and west lose a larger percentage in winter, but absolute values are low (winter generation is always weak in the UK). The real impact on annual output is the summer loss (~13–17%), which is milder than winter.

In other words: yes, orientation matters more in winter, but winter is already such a weak season that the absolute penalty is modest.

Combining Orientation with Other Factors

Orientation doesn't exist in isolation. Here's a quick interaction matrix:

Worst case scenario: North-facing + East/West (only 45° better than due north). ~500 kWh/year = payback 6+ years. Avoid.

Best case scenario: South-facing + unshaded + ToU tariff + battery. ~1,000 kWh/year equivalent value (with storage) = payback 2.4 years.

The Simple Question: Should I Accept East/West?

If it's your only option: Yes. Payback is 4.2 years (vs 3.1 for south), but you still make money over 25 years. Just be clear-eyed about the longer timeline.

If you can wait for south or south-east: Do. The 1-year payback difference adds up to £250–£300 of extra lifetime profit.

If you can optimize elsewhere: Yes. A poor-aspect system on a good tariff (Octopus Flux) or with high self-consumption can beat a perfect south-facing system on a poor tariff (Economy 7, 0p export).

See the tariff guide for advice.

How to Find Out Your Roof's Aspect

1. Use the Solar Report – our tool tells you your building's aspect and sun-exposure grade.
2. Check Google Earth / Maps – rotate the view and look at shadow angles. South-facing roofs have long winter shadows (north side of house); north-facing roofs have shadows on the south side.
3. Physical inspection – stand at your property at solar noon (1pm GMT, 2pm BST) and note where the sun is. If it's roughly in front of you, you're facing south.
4. Compass app – point your phone at your roof surface. Most phones have a compass app that shows azimuth in degrees.

Key Takeaways

• South-facing is 100% baseline – generates the most solar energy across the year.
• South-East/South-West loses ~5% – nearly as good as due south. Go for it if you have it.
• East/West loses ~25% – still viable, but payback extends to 4.2 years. Worth doing if it's your only option; worth waiting for south if you have a choice.
• North-facing loses ~40%+ – not recommended for plug-in solar. Look for alternative placements.
• Tariff and self-consumption matter more than orientation – a west-facing system on Octopus Flux can beat a south-facing system on Economy 7.
• Combine with the Solar Report – check your property's sun exposure grade before committing to aspect calculations.

Ready to assess your property? Run the Solar Report to see your orientation and sun-exposure grade, then use the calculator to model your exact aspect.