Every direction, in kWh per kW
An east or west roof in Manchester makes around four-fifths of what the same panels would make facing south. The figures below come from PVGIS 5.3 for a point in the city centre, using satellite weather data for 2005-2023 and the same allowance for system losses on every row (PVGIS). Each is the yearly output, in kWh, for one kW of panels.
| Roof faces | 30° pitch | 35° pitch | Share of a south roof at 35° |
|---|---|---|---|
| South | 880 | 886 | 100% |
| South-east | 839 | 842 | 95% |
| South-west | 828 | 830 | 94% |
| East | 726 | 717 | 81% |
| West | 712 | 702 | 79% |
| North-east | 592 | 567 | 64% |
| North-west | 583 | 558 | 63% |
| North | 530 | 494 | 56% |
| Flat, panels laid level | 745 | 84% | |
Figures from PVGIS 5.3. Shares are our arithmetic, against 886 kWh per kW for a south roof at 35°.
Two points are easy to miss. First, the step from due south to south-east or south-west is small: 842 and 830 against 886. Second, east and west roofs do better at a shallower pitch. At 30° an east roof makes 726, more than at 35°, and at 10° PVGIS gives 744. So ask any installer to model your actual pitch rather than a standard one.
Flat roofs sit in between. Laid level, panels make 745 kWh per kW, about 84% of a south roof at 35°. In practice panels on a flat roof usually go on frames. Tilting them towards the south raises the output per panel, while a low frame with rows facing east and west fits more panels into the same space. On a house, permitted development lets flat-roof panels rise 0.6 m at most over the roof's top, so frames have to stay low. Back extensions and dormers in Chorlton and Withington are where flat roofs most often come up.
You can try any combination of direction and pitch in the roof yield explorer, which draws on the same data set.
Close in summer, behind in winter
East and west roofs lose most of their ground in winter, not in summer. In June PVGIS gives an east roof at 35° 106 kWh per kW against 111 for a south one, about 95% as much. In December the figures are 11 and 28, about 39% (PVGIS, our arithmetic).
The reason is the sun's path. In midsummer it rises north of east and sets north of west, so both slopes get hours of direct light. In midwinter it rises in the south-east, stays low and sets in the south-west. An east or west slope then sees it only at a glancing angle.
| Month | South | East | West | North |
|---|---|---|---|---|
| March | 78 | 58 | 56 | 28 |
| June | 111 | 106 | 104 | 91 |
| September | 81 | 64 | 63 | 35 |
| December | 28 | 11 | 11 | 6 |
So an east or west roof is a summer-weighted system. Through the long days it keeps pace with a south roof surprisingly well. In the dark months it covers a smaller share of the house's needs, and a household weighing it up should expect that.
Panels on both slopes: east and west together
Where a roof has one slope facing east and one facing west, panels can go on both. Each side then works at a different time of day.
- East panels start early and peak in the morning, which suits a household that cooks breakfast, runs the shower and charges things before leaving.
- West panels peak in the afternoon and run on into the evening, which suits a household that comes home and cooks around teatime.
- Together they give a lower midday peak and a longer working day than a single south-facing array.
Across the year, a system split evenly between the two slopes would make about 710 kWh per kW, by our arithmetic from the PVGIS figures above. To match one kW facing south you would need about 1.25 kW split between east and west. That usually means more panels, and so a higher price for the same yearly kWh. The cost guide gives the North West price per kW to set against it.
Which slope is better on its own? PVGIS gives east a slight edge here, 717 against 702 at 35°, but the difference is small enough that daily routine should decide. A household out all day and home for the evening gets more direct use from a west slope.
There is a technical point to check in any quote. Panels on two slopes see different light, so they should not share one string on one input. The usual answer is an inverter with two separate inputs, often called MPPTs, or optimisers fitted behind the panels. Ask which the quote uses and why.
A split array also makes the grid limit easier. Because the two sides rarely peak together, their combined output seldom reaches the full panel rating, so more panels can sit behind an inverter within the 3.68 kW single-phase limit for G98. The grid connection guide explains that rule.
Hipped roofs on Burnage and Wythenshawe semis
Many inter-war semis have a hipped roof: front and back slopes, plus a sloping end where a gable would otherwise be. That shape gives faces in more directions, but each one is smaller, and the hip end is a triangle that wastes space at its edges.
Manchester has a great many of them. Burnage is the city's most semi-detached ward, with 63.5% of households in a semi. The Wythenshawe wards come next. The council built Wythenshawe up from the 1920s as its "Garden City", and today Sharston stands at 43.1%, Baguley at 41% and Woodhouse Park at 34.8% (ONS Census 2021, ward level).
On a semi, which slope faces where depends on the road. Where a road runs north to south, the front and back slopes face east and west and the hip end faces north or south. Where it runs east to west, one main slope faces south and the hip looks east or west. Curving garden-city roads mean that neighbouring houses can face quite different ways.
Practical points for a hipped semi:
- Count whole panels, not roof area. A hip end may take only a few panels once its edges and triangular shape are allowed for.
- Compare per panel and in total. A south-facing hip end can beat a bigger east or west slope panel for panel, while the bigger slope still gives more overall.
- Plan for two orientations, which brings back the inverter question above.
Panels on a house roof are normally permitted development. They must sit within 0.2 m of the roof surface and must not rise above its highest point (SI 2026/896). The planning guide covers the exceptions.
Terraced rows with east and west slopes
Where a terraced street runs north to south, every house on it has one slope facing east and one facing west. Terraces are a big part of the city: 28% of Manchester households live in one. Moss Side leads at 56.3%, followed by Levenshulme (51.1%) and Gorton & Abbey Hey (47.3%), on Census 2021 figures.
On those streets the choice is between two modest slopes, each broken up by chimney stacks on the party walls. The front slope faces the street, so scaffolding there usually stands on the pavement. The rear slope is often reached from a back yard or alley instead.
A low-pitched rear roof, where a house has one, can help. At a shallow 10° pitch direction matters far less: PVGIS gives 807 kWh per kW facing south, 744 east, 738 west and even 671 north. A shallow roof is the one place where a north-facing panel is worth thinking about.
If the street runs east to west instead, one slope faces south and the other north. Then the south slope does the work, and a steep north slope is a weak case at 494 kWh per kW. The terraced house guide covers access, stacks and party walls in more depth, and the installer checklist lists what a quote for a two-slope design should show.