How much less do north-facing panels generate?
In the UK, a south-facing roof at an optimal pitch (30–35°) is used as the 100% benchmark. An east- or west-facing roof at the same pitch generates roughly 80–85% of the south-facing output. A north-facing roof at the same pitch generates approximately 50–60% of south-facing output.
Over a year, a 4 kWp south-facing system in southern England might generate around 3,600 kWh. The same system north-facing would generate closer to 1,800–2,200 kWh — just over half. The financial return scales proportionally.
The gap narrows somewhat in summer because the sun is high in the sky and illuminates north-facing surfaces more directly during the longest days. In winter, north-facing panels receive almost no direct sunlight and generate very little.
Tilt angle matters more on a north-facing roof
A steeply pitched north-facing roof (45° or more) generates significantly less than a shallow pitch because the panels face even more directly away from the sun. If your north-facing roof slope is shallow (15–25°), the output penalty is less severe than a steep slope.
Some installers fit flat or low-tilt mounting systems on north-facing slopes to tilt the panels back towards the south, effectively overriding the roof orientation. This works structurally but adds cost, increases wind loading, and may not be permitted in conservation areas or under permitted development rules.
When north-facing solar is still worth considering
If the property has no south-, east-, or west-facing roof space — for instance a terrace or mid-terrace property with a strict north/south ridge — north-facing panels may be the only option.
If electricity consumption is high during winter mornings (when north-facing panels still receive some diffuse light) and you are primarily targeting self-consumption rather than maximising generation, the economics may still make sense at a lower system size.
A properly sized, modestly priced system on a north-facing roof can still pay back over its lifetime, but the payback period will be longer — 12–18 years versus 7–10 years for a south-facing equivalent. The investment case needs to be modelled on realistic north-facing generation figures, not the default south-facing estimates some installers quote.
Better alternatives if you have a choice
If the property has both north- and south-facing slopes, always prioritise the south-facing side. A smaller system on the south slope will outperform a larger system on the north slope.
East-west split installations — panels on both the east and west slopes — generate 80–85% of an equivalent south-facing system but spread the generation across more of the day, which can improve self-consumption for households with morning and evening peaks. Many installers prefer this configuration for properties without a usable south slope.
Ground-mounted systems in the garden, carport canopies, or outbuilding roofs can be oriented optimally regardless of the main property roof direction. These add cost but restore the full south-facing generation potential.