How east-west installations work
An east-west installation places panels on both the east-facing and west-facing roof slopes, typically at the same pitch. The east panels capture morning sun from roughly sunrise to early afternoon; the west panels take over from mid-morning through to sunset. Together they cover most of the day's daylight hours.
The total annual generation from an east-west split is typically 15–20% lower than an equivalent south-facing installation, because neither slope receives direct perpendicular irradiance at solar noon. However, the generation profile is significantly flatter across the day — a characteristic that has practical and financial implications.
The self-consumption advantage
A south-facing system produces a sharply peaked generation curve centred around solar noon. For households where consumption is also highest around noon (or where a battery is present to shift it), this is optimal. But for working households where consumption peaks in the morning and evening, the noon peak from a south-facing system largely goes to export rather than self-consumption.
An east-west installation produces earlier morning generation (useful for morning routines and EV charging before commuting) and later afternoon/evening generation (useful for cooking, heating, and evening usage). The self-consumption fraction of an east-west system is often higher than its south-facing equivalent, even though total generation is lower.
For homes with high morning and evening consumption patterns, modelling the self-consumption fraction against both options is worthwhile before assuming south-facing is always superior.
Structural and planning considerations
East-west installations typically use lower tilt angles (15–25°) than south-facing pitched roof installations (typically 30–40°). Lower tilt reduces wind loading and is sometimes preferred by structural engineers for older or lighter roof structures. This is worth discussing with your installer if you have any concerns about roof loading.
An east-west installation on a ridge with both slopes accessible falls within standard permitted development (assuming the panel projection and height conditions are met for each slope independently). Planning permission is not normally required.
Snow shedding is slower on lower-tilt panels, which can extend the duration of winter snow coverage compared to a steeply pitched south-facing installation. This is a minor factor in most UK locations.
Inverter configuration
An east-west installation should normally use either a string inverter with two MPPTs (maximum power point trackers) — one input for each slope — or microinverters/power optimisers on each panel. Using a single MPPT for both slopes produces significant mismatched-string losses because the east and west panels are never at their individual maximum power points simultaneously.
Ensure your installer quotes an appropriate inverter configuration for an east-west split. A single MPPT string inverter on an east-west system is a common oversight that can reduce output by 10–15% relative to correctly configured dual-MPPT equipment.