By installing a PV system, homeowners can generate their own 'green electricity', thus reducing electricity bills and also helping to offset carbon emissions.  As PV is completely pollution free, installing a small domestic system of around 1.5 kW would provide around 1000 kWh of electricity every year, which would save around half a tonne of CO₂ annually.

PV is a very practical and versatile option for renewable electricity generation and is almost universally applicable.  Systems can be integrated into, or mounted on, an existing building structure, thereby creating minimal visual intrusion.  The systems run silently and after the initial installation costs, there are no further fuel costs.  For new buildings the cost of PV will offset the cost of roofing or cladding materials.  Also, as PV systems are modular, they can be added to at any time.

Will it supply all my electricity?

The electrical output of a PV cell is dependent upon the intensity of the light to which it is exposed. So PV cells will tend to generate more electricity on bright days than when skies are overcast. However, photovoltaics do not need to be in direct sunlight to work, so even on overcast days a PV cell will be generating some electricity.

The average household consumption in the UK is 3300 kWh per annum. Thus, on average a 2kWp system would supply around 50% of your electricity over the course of the year, though it may be possible to do more by carefully controlling your energy use.

How much does it cost?

PV is an expensive technology, although the price of a PV module has fallen significantly over the last 20 years, from around £15 per Wp in 1980 to current prices of around £8 per Wp. That means that a single module, typically generating 50W of power under standard test conditions, now costs around £150-£200.

The cost of a complete PV system can vary greatly depending on the equipment and installation prices, so a generalisation is hard to make.  Sundance estimate that a standard domestic system would cost around £5000 with grant assistance - for more information on the available grant aid, visit www.est.org.uk.

How long will they last?

Systems are expected to have a life of 25 years with very low maintenance - routine cleaning forming part of normal building maintenance.  Many systems today are provided with operation and power output guarantees for the lifetime of the equipment.  The electronic control equipment is the most unreliable part of the system.

Will I need planning permission?

Not usually, but if you live in a listed building or in a conservation area, you may need consent.  Contact your local authority planning department for advice and also check if building regulations might apply.  If there are problems installing the panels on the roof, it might be possible to put a system in the grounds of your house.

What does 'grid-connected' mean?

The main area of interest in the UK today is grid connect PV systems. These systems are connected to the local electricity network. This means that during the day, the electricity generated by the PV system can either be used immediately (which is normal for systems installed on offices and other commercial buildings), or can be sold to one of the electricity supply companies (which is more common for domestic systems where the occupier may be out during the day). For more information about green tariffs and electricity supply, visit www.greenelectricity.org.  In the evening, when the solar system is unable to provide the electricity required, power can be bought back from the network. In effect, the grid is acting as an energy storage system, which means the PV system does not need to include battery storage.

Connecting a PV system to the distribution network will require permission from the Distribution Network Operator (DNO). The DNOs in the UK have different policies when it comes to connecting PV systems to their networks, and so different rates will be paid for exported electricity. The system installer will make the necessary arrangements for grid connection.

What are the environmental aspects?

PV is emission free and requires no fuel or cooling water.  It is a silent operation and so is very suitable for installation in urban areas.  The manufacture of the panels uses potentially harmful substances but industrial production techniques and equipment are used to minimise this.  PV modules can be made to be practically 100% recyclable.

Are there many solar PV systems in the UK?

It is estimated the PV is now producing about 1MW of electricity in the UK.  One of the largest arrays can be seen in the Centre For Alternative Technology, Machynlleth, and there are many hundreds of domestic sized systems around the UK.  In other parts of Europe the numbers of systems are much greater than in the UK.  The recent Government grant support for PV is designed to help us catch up - In London for instance, Ken Livingstone has instigated a programme to install solar panels on the majority of new housing being built across the capital.