It used to be that Photovoltaic (or solar) panels were expensive and difficult to install, but that is no longer the case. Prices have dropped massively and together with today's high electricity prices, they can pay for themselves within a few years.
Many of our projects, incorporate these panels on the roof, and when we design new houses we try and ensure that at least one of the roofs face south.
There are a wide range of panels which we consider, taking into account the style of the roof, whether the property is in a conservation area or is a listed building etc. Generally panels are considered 'permitted development' and don't need planning permission, provided we make sure they don't have a major impact on the appearance of the house from the road.
They should not be installed above the ridgeline and should project no more than 200mm from the roof or wall surface.
If your property is a listed building installation will require planning permission and is likely to require an application for listed building consent.
If your property is in a conservation area, planning consent is required when panels are to be fitted on the principal or side elevation walls and are visible from the highway. If panels are to be fitted to a building in your garden or grounds they should not be visible from the highway and therefore OK.
If being installed on a flat roof, solar panels are subject to the following conditions:
panels cannot be sited within 1 metre of the external edge of the roof; or
panels cannot protrude more than 1 metre above the plane of the roof.
To run through a few examples:-
The most cost effective photovoltaic panels area standard panel array (ideally 12 or more) fitted onto the roof using clips or a subframe, as it is being built. The roof should ideally face south, but east and west facing roofs will work too, although they are less efficient, only generating electricity when the sun shines on them. The roof should not be shaded by trees or other buildings.
Alternatively the panels can be fitted directly to the structure instead of the roof finish. This is called an 'inroof' system and the panels form the roof waterproofing layer. The advantages of this are you are not paying for a roof finish (such as tiles or zinc) which will never been seen, it is are under the photovoltaic panels.
Where the project is in a sensitive location or a listed building, we have used photovoltaic slates (tiles are also available) which can hardly be differentiated from the adjacent tiles. These are more expensive and not so efficient but can still generate a good level of electricity. The panels below from The Pound roof disappear in wet weather and were approved by the planners for use in the Llandaff Conservation area, facing the Scheduled Ancient Monument - The Bishops Palace
We have also located Photovoltaic panels in adjacent fields, and are looking at using them as a shading device (Brise Soleil) on south facing windows.
Finally, if the panels are used in conjunction with battery storage, they can be even more efficient, storing electricity which can be fed back to the house when the sun stops shining.