This is one of the biggest myths in solar. A lot of people believe panels only work properly on a south facing roof, and that if your roof faces the wrong way you are out of luck. That is not true. South facing is the ideal, but it is far from the only option, and in some cases another orientation actually works out better. Let me explain how roof direction affects output and why your roof almost certainly will take solar.
The orientation figures
The easiest way to think about this is in rough percentages. Imagine a perfect south facing panel produced 100 percent of what it possibly could. Here is roughly how the other directions compare in the UK:
- South facing: around 100 percent. The ideal. The sun tracks across the southern sky, so a south roof catches light all day.
- East facing: around 75 percent. Strong morning production as the sun comes up.
- West facing: around 75 percent. Strong afternoon and evening production as the sun goes down.
- North facing: around 50 percent. Less per panel, but still real, usable electricity.
So even a north facing roof, the worst case, still gives you half of best case output. That is a long way from useless.
If your roof does not face south
The answer here is simple. If your roof does not face south, you put the panels on a different roof, or you accept a slightly lower output from the roof you have. There is almost always a sensible option.
We very often fit panels on east and west facing roofs, and there is a hidden advantage when we do. You usually get double the roof area to play with. A house with east and west pitches can take panels on both, so although each panel works at around 75 percent, you can fit roughly twice as many of them. The total output often lands close to a smaller south facing array, and you get a flatter production curve across the day rather than one big midday peak.
That flatter curve can suit your usage better. Morning sun from the east covers breakfast and getting ready. Afternoon and evening sun from the west covers the time you are home and cooking. With east and west you are generating when you are actually using power.
When north facing makes sense
This surprises people, but we do sometimes fit panels on a north facing roof, and it can be the right call.
Picture a fully electric home. The south facing roof has a dormer window stuck in the middle of it, so you can only squeeze a handful of panels up there. Meanwhile the north facing roof is completely clear, a big open expanse with nothing in the way.
In that situation, filling the clear north roof gives you far more total panels than the broken up south roof ever could. Each panel produces less, but you have so many more of them that the system as a whole produces a healthy amount. For an all electric house that needs every kilowatt hour it can get, that is fantastic. More panels at 50 percent can beat a few panels at 100 percent.
The point is that orientation is one factor among several. Roof space, shading, obstructions like dormers and chimneys, and how much electricity you use all feed into the design. A good survey weighs all of it rather than fixating on the compass.
Panels keep getting better
There is another reason orientation matters less than it used to. Panels have improved enormously, so a less than perfect roof still produces plenty.
Over the years the cost of solar has come down sharply. You tend to pay a similar amount per panel but get far more power out of it. To put numbers on it:
- Older panels were around 275 watts each.
- The panels we fit now are around 465 watts each.
- New panels coming through are approaching 472 to 480 watts.
That means an east, west or even north facing array today can comfortably outproduce a south facing array fitted ten years ago. The roof you have is very likely good enough.
What about shading and pitch?
Direction is only part of the story. Two other things shape how well a roof performs, and they are worth a quick word.
The first is shading. A chimney, a tall tree or a neighbouring building that throws shade across the panels for part of the day will cost you more than facing slightly off south. A good survey looks at where the shadows fall through the day and across the seasons, then designs around them. Sometimes that means choosing one pitch over another, or laying the panels out to keep the shaded ones off the worst spots.
The second is pitch, the angle of the roof. In the UK a pitch of around 30 to 40 degrees is close to ideal, but most roofs sit comfortably in a workable range. A shallow or flat roof can still take panels, often mounted on frames to tilt them towards the sun.
The point is that no single factor decides whether your roof suits solar. Direction, shading, pitch and roof space all feed into the design together, which is exactly why a proper survey beats any rule of thumb.
The bottom line
You do not need a south facing roof for solar to be worthwhile. South is the ideal at around 100 percent, east and west sit at around 75 percent but often give you double the panels, and even a north facing roof at around 50 percent has its place on an all electric home with a clear pitch. The right answer comes from a proper survey of your specific roof, not a rule of thumb. We design systems to suit the roof you have across Cambridgeshire, Bedfordshire and Northamptonshire. If you have been told your roof faces the wrong way, get a second opinion. Call the office on 01480 400607 or request a survey through our website.
Jason Pope
Owner, Selec Group