Is my house suitable for solar panels?

How much sun?

The amount of power that solar panels produce is proportional to the amount of sunlight they get. If placed on a south-facing roof, they will therefore generate more electricity than an east- or west-facing roof. Shading will also make a difference, and significant shading will considerably reduce the output from your array.

The difference from orientation and tilt isn't as large as you might imagine. An east- or west-facing roof, if at a fairly shallow pitch, will generate only about 20% less electricity than an array at the optimum angle; between south-west and south-east you only lose about 5%.

Even vertical walls can be used to mount solar panels. The return from south-facing vertical panels is about 72% of their output at the optimum angle; the return from east or west facing vertical panels is about 54% of the potential maximum.

So although south is certainly the best option, it may well still be economically worthwhile even if you don't have a south-facing roof.

Not everyone has a perfect roof - but if yours has a potential return of at least 70% of the potential maximum after the effects of shading and orientation are taken into account, then it's quite likely to be economically sensible to install solar panels.

Even if nowhere is suitable for an array on the building itself, it may well be possible to mount an array on a mast in the grounds instead. Note however that the subsidies given by the government are higher for building-integrated systems.

Roof type

Solar panels can be fastened to most roof types. Conventional framed panels are the most cost-effective solutions for tiled or slate roofs. For 'standing-seam' roofs, the Unisolar peel-and-stick panels are a great alternative. For flat roofs, it's generally best to use mounting frames to fix the panels at an angle so that they catch more sun, and so that rain will wash dirt off more effectively.

Planning permission

Planning permission is not generally required for solar arrays. However, it may be needed if your building is listed, or if you are in a conservation area. If that is the case, you should contact your local planning department to ask if you would need to apply for permission.

Size of array

The bigger the area available, the more power you will get. You can calculate the approximate peak power of the largest solar array you can fit on your roof by multiplying the area available (in m2) by 130. If you have a space 5m x 4m available for example, you have 20m2, so the maximum array size is around 2600W. Because modules only come in particular sizes however, you may not be able to use the whole space.