Energy statements

Solar photovoltaic cells (PV cells) convert sunlight into electricity. PV cells consist of semiconductor materials, usually silicon, that convert sunlight into electrical energy through the photovoltaic process.

Photovoltaic cells should be positioned in a location that is not the subject of shading by other objects such as trees or tall neighbouring buildings. In addition the ideal position is south facing. There is still sufficient sunlight to be utilised between a south-westernly aspect and a south-easterly aspect, although the efficiency of the system will reduce.

In Britain photovoltaic systems for domestic use are generally roof mounted. Traditionally this took the form of roof mounted racks of solar panels containing photovoltaic cells. Nowadays panels that can be placed directly upon the roof decking are available and even panels that can be directly integrated within the roof and partially replace conventional roof decking.

Photovoltaic cells can also be attached to or integrated within the walls of a building. This solution is more suited for taller buildings where the roof area in comparison to the net usable area is much smaller than in conventional houses.

A photovoltaic cells system with an output power of between 1.5 and 3 kWp is usually sufficent to provide all or the majority of the electricity needs of a dwelling in the UK. Such a domestic system costs around £5,000- £7,500 per installed kWp. Solar tiles cost more than conventional panels and panels that are integrated into a roof are more expensive than those that sit on top.

Solar photovoltaic cells: how it works

For most dwellings, the production of the electricity through a photovoltaic cells system is usually not simultaneous with its use. To enable maximum benefit of the installation, excess electricity can either be fed into the national electricity grid or it can be stored using batteries.

When the photovoltaic system is connected to the grid the dwelling will draw its electricity from the grid at times when there is a higher need for electricity then the cells are producing. Electricity companies in the UK pay for the export of electricity to the grid. The tariffs for exporting and importing electricity usually differs and it is worthwhile to explore the offers from a number of electricity companies.

Solar photovoltaic cells: How much does it save

The amount of electricity that can be generated depends on the availablility of suitable roof space. For some dwellings it will be possible to generate the entire electricity demand of the building. It should be noted though that, with a grid connected system, even if 100% of the electricity that is used in the dwelling is generated using photovoltaic cells, in most cases there is still a remaining electricity bill, although this will be significantly lower. This is because the electricity company will charge a higher tariff for electricity delivered to the building than that it will pay for electricity delivered to the grid. In addition there will be a standing charge in place.