Choosing a Site, Planning Permission and Installations.
Choosing a site
Orientation and tilt
Your roof should ideally face due south at a pitched angle of around 30° from the horizontal to give the best overall annual performance. Installations at any pitch and facing anywhere to the south of due east and due west are feasible, although output and income will be reduced. Installation is not recommended on roofs facing north.
Seasonal performance
The chart below shows a typical seasonal spread of energy generation for a system of 2.9kWp facing south. The winter months generate significantly less electricity compared to the summer months.
Site location
The amount of electricity generated by a solar PV system can also vary depending on where you live. Northern areas receive slightly less energy from the sun over the year. For example, a 1kWp system will generate less electricity in Northern Scotland than it would in Cornwall. However, solar electricity is still worthwhile - the differences aren’t substantial.
Shape of roof area
Solar PV arrays are made up of modules of about 1.5 square metres which allows most available roof shapes to be accommodated. Typical UK installations are around 15 to 25 square metres. For example, a 2.9kWp system could comprise 15 panels taking up an area of 20 square metres and will generate roughly 2,450kWh per annum.
Shading
All the modules are connected, so any shading on a single module will affect the performance of the whole array. A system can tolerate some shading early or late in the day without much reduction of overall output but it should not be shaded between 10am and 4pm. Nearby trees, chimneys, TV aerials and vent pipes are all common causes of shading and should be accounted for before any installation.
Solar electricity doesn’t necessarily require direct sunlight and can still generate electricity on cloudy days. You could get as much as a third of the energy on a cloudy day as you would get on a sunny day at the same time of year.
Structure and Building Regulations
When installing a solar hot water system building regulations will apply. This is in part to ensure that your property can support additional load, both internally and on the roof.
Before proceeding with the installation, you must check with your Local Authority Building Control officer that all proposed work is compliant with current building regulations.
Please note that there may be additional costs associated with building control notification.
Planning permission
In England, Wales and Scotland, you don't need planning permission for most home solar electricity systems, as long as they're below a certain size - but you should check with your local planning officer, especially if your home is a listed building, or in a conservation area or World Heritage Site - we can only give general guidance here. You'll find full details on the Government's relevant legislation sites.
England - General Permitted Development Order (GPDO)
Scotland - Town and Country Planning (General Permitted Development) (Domestic Microgeneration) (Scotland) Amendment Order 2009
Wales - The Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2009)
Permitted development rights for solar PV (roof mounted)
Permitted unless:
panels protrude more then 200mm when installed.
Your local Building Control Office may want to check that your roof structure is suitable – your installer should be able to advise on this.
Scotland
In Scotland, permitted unless:
installed on any part of the external walls of the building if the building contains a flat panels when installed on a flat roof are situated within 1 metre from the edge of the roof or protrude more than 1 metre above the plane of the roof panels when installed project higher than the highest point of the roof (excluding the chimney)
the building is within a conservation area or World Heritage Site and the solar PV or solar thermal equipment is installed on a roof which forms the front of the building and is visible form the road.
The solar PV equipment must, as far as is reasonably practical, minimise its effect on the amenity of the area and be removed when it is no longer needed or used for domestic microgeneration.
Installation
Installing solar PV systems is fairly disruption-free and most systems are installed in two or three days. Unless your building is single storey, you'll need to have scaffolding put up.
The next step is usually to bolt the panels to the roof, with the electrical wiring coming last. The installer should inform your District Network Operator to get permission to connect your system to the national grid. They will then register the site with the Microgeneration Certification Scheme ('MCS'), and you will get a certificate by email which you can use to claim Feed-in-Tariffs.
The installer should also:
1, how you how to operate the system and how to spot faults
provide information on maintenance requirements
2, give you a pack with all the manuals and warranties, etc.
