Panel installation and wiring
East-West Solar Arrays in the UK: When Splitting Your Panels Pays Off
Most solar installers default to south-facing panels because they produce the highest total annual output. But for many UK homes, splitting panels across east and west pitches can increase self-consumption, reduce battery requirements, and work out better financially even though total generation is lower.
1. Understand what an east-west array actually is
A south-facing array produces one broad peak of power around solar noon, typically between 11 am and 2 pm. An east-west split uses two roof pitches facing in opposite directions. The east-facing panels start generating early in the morning; the west-facing panels carry on into the late afternoon and early evening. The combined output curve is flatter and longer than a south-facing peak, often running usefully from around 7 am to 7 pm in summer.
The trade-off is total annual yield. An east-west array typically produces around 15 to 20 percent less total energy over the year than the same number of panels all facing south. Whether that loss matters depends on how you use the electricity you generate.
2. Check whether your roof actually suits a split array
Not every house with east and west roof pitches is a good candidate. The key questions are:
- Pitch angle: East and west pitches below about 15 degrees offer little directional advantage. Between 20 and 40 degrees is ideal.
- Orientation: Pitches within about 45 degrees of true east and west respectively will perform reasonably well. A south-east and south-west split still sees a midday dip but is better than pure east and west.
- Shading: Morning shading on the east face (a neighbour's chimney, a large tree to the east) undermines the early-generation benefit. Get a shading assessment for both faces, not just one.
- Available area: You need enough panels on each face to make the split worthwhile. A system that is mostly south-west with two east panels misses the point.
3. Compare the generation profile with your household's usage
The self-consumption benefit of an east-west array is most pronounced in households that use electricity in the early morning (electric showers, kettles, dishwashers) and again in the late afternoon and evening (cooking, laundry, TV). A south-facing system that peaks at midday when the house is empty wastes most of that midday surplus to the grid at a low Smart Export Guarantee rate unless a battery captures it.
An east-west array does not produce that same large midday surplus to capture. Instead, it trickles generation into the house from early morning onwards and stays useful into the early evening, matching more naturally with when people are actually home. Some households find this increases their self-consumption rate from around 30 to 40 percent (south-facing, no battery) to 50 to 60 percent (east-west, no battery).
East-west vs south-facing: a rough comparison
- South-facing 4 kWp, no battery: High total output, low self-consumption (30-40%), large midday export
- East-west 4 kWp, no battery: Lower total output (-15 to -20%), higher self-consumption (50-60%), smaller battery needed
- South-facing 4 kWp, with 5 kWh battery: Best total output, high self-consumption, higher upfront cost
For households that cannot afford or do not want a battery, an east-west layout can outperform a south-facing array on the measure that actually appears on the electricity bill: units self-consumed.
4. Size a battery to the flatter generation curve
If you do pair an east-west array with a battery, you usually need less storage than a south-facing system would require. A south-facing array can produce 3 to 5 kWh of surplus in two or three hours around midday; capturing all of that needs a battery to match. An east-west array spreads that same surplus over a much longer window, so the instantaneous generation rarely exceeds what the house is using, meaning less surplus accumulates at any one time.
A 5 kWh battery is often sufficient to capture the afternoon west-facing surplus for evening use. A 7 to 10 kWh battery makes sense if you are also charging an EV overnight or running night-rate loads that you want to cover from stored solar. Larger batteries than that are rarely justified by an east-west array alone.
5. Check the inverter and G98/G99 implications before you design
An east and west orientation on separate roof planes almost always requires a dual-MPPT inverter, which has two independent maximum power point trackers to handle the different generation curves from each face. If you use a single-MPPT inverter with both orientations combined on one string, the tracker will compromise between the two, reducing output from both.
The total system capacity still counts toward your DNO notification threshold. On a standard single-phase UK supply, a solar inverter up to 3.68 kW AC can go in on a G98 notification (which your MCS installer submits on your behalf). Larger systems need a formal G99 application, which can take several weeks. If your east-west design needs 4 kWp or more to make commercial sense, account for the G99 timeline in your project plan.
Frequently Asked Questions
Is an east-west array less efficient than south-facing?
In total annual output, yes, typically around 15 to 20 percent less for the same number of panels. But efficiency is not the only measure. An east-west layout can increase self-consumption by matching generation to when people are actually home and using power, which sometimes means better financial returns even with lower total generation.
Can I add east and west panels to an existing south-facing array?
Yes, but it usually requires a dual-MPPT inverter or a second inverter to handle the separate orientations cleanly. Adding a second orientation to a single-MPPT string inverter will underperform both strings. An MCS installer can advise on whether your existing inverter can accommodate a new string or whether a replacement is needed.
Does an east-west setup need planning permission?
In most cases, no. Roof-mounted solar panels on a standard domestic property fall under permitted development in England, including east or west-facing installations, as long as they do not project more than 200 mm from the roof plane and the property is not a listed building or in a designated area where stricter rules apply. A conservation area or article 4 direction may require householder permission.