Roof orientation and tilt are two of the first things a UK solar installer assesses. Together they determine how much of the available sunlight your panels can capture across the year. Understanding the fundamentals helps you make an informed decision — and pushes back on any installer who tells you a non-ideal roof simply is not worth considering.
The Benchmark: South-Facing at 35 Degrees
For a UK location (approximately 51–58 degrees latitude), the optimal solar panel setup is:
- Orientation: True south (180 degrees azimuth)
- Tilt: 30–40 degrees (35 degrees is widely cited as optimal for UK latitudes)
At this configuration, a well-specified 4 kWp system in the south of England might generate 3,600–3,900 kWh per year. In Scotland, that same system might produce 3,100–3,400 kWh.
This is the baseline against which all other orientations are measured.
South-East and South-West: Minimal Penalty
Diverging 45 degrees from true south — to south-east or south-west — reduces annual generation by approximately 5–8%. In practical terms, this is marginal. The vast majority of UK semi-detached and terraced properties with roofs facing south-east or south-west should proceed with confidence.
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East-West Split Roofs
Many UK properties have a ridge running north-south, meaning one roof slope faces east and the other faces west. An east-west installation produces:
- Approximately 80–85% of the annual yield of an equivalent south-facing setup
- A broader generation profile across the day — morning peaks on the east slope, afternoon peaks on the west
- Better alignment with household energy demand, as morning and evening consumption tends to be higher than midday
East-west installations often have a better self-consumption rate than pure south-facing arrays, which can produce surplus at midday when nobody is home.
Flat and Low-Pitch Roofs
Flat roofs require mounting frames to tilt panels at an appropriate angle. In the UK, 15–25 degrees is commonly used for flat roof installations, balancing generation efficiency against wind loading. Even at 10 degrees, annual yield reduction versus the 35-degree optimum is only around 10–12%.
For very low-pitch roofs (below 10 degrees), self-cleaning via rainfall becomes less effective, meaning cleaning frequency should be factored into the maintenance plan.
Orientation and Generation: UK Summary Table
| Orientation | Pitch | Relative Generation | Notes |
|---|---|---|---|
| South (180°) | 35° | 100% (baseline) | Optimal for UK |
| South-East/South-West | 35° | 92–95% | Excellent |
| East or West | 35° | 80–85% | Good; flatter demand curve |
| North-East/North-West | 35° | 65–75% | Marginal; assess carefully |
| North | 35° | 50–60% | Generally not recommended |
| Any | Flat (0°) | 85–90% | Minimal shading risk |
| Any | 15° (low pitch) | 90–95% | Common on bungalows |
Shading: The More Important Variable
For UK installations, shading often matters more than orientation. A south-facing roof with significant shading from a chimney stack or neighbour's extension can underperform a west-facing unshaded roof. Always request a shading analysis using tools such as Solargis or PVGIS as part of the quotation process.
Products like SolarEdge power optimisers and Enphase microinverters are specifically designed to mitigate shading loss at the individual panel level — worth considering if partial shading is unavoidable.
North-Facing Roofs: When to Say No
A true north-facing roof in the UK will produce 50–60% of a south-facing equivalent. The economics are usually marginal unless:
→ Before you read on — see what payback looks like for your roof in under a minute.
- Electricity prices are very high
- The available roof area is very large
- The property has specific reasons (planning, tree cover) limiting south-facing access
In most cases, a north-facing-only installation is not recommended for a UK homeowner prioritising return on investment.
