An Energy Performance Certificate (EPC) will be required for all homes whenever built, rented or sold.

If you are buying or selling a home it is now law to have a certificate. This will be extended to rented homes from October 2008.

The certificate records how energy efficient a property is as a building and provides A-G ratings. These are similar to the labels now provided with domestic appliances such as refrigerators and washing machines.

They are produced using standard methods and assumptions about energy usage so that the energy efficiency of one building can easily be compared with another building of the same type. This allows prospective buyers, tenants, owners, occupiers and purchasers to see information on the energy efficiency and carbon emissions from their building so they can consider energy efficiency and fuel costs as part of their investment.

An EPC is always accompanied by a recommendation report that lists cost effective and other measures (such as low and zero carbon generating systems) to improve the energy rating. A rating is also given showing what could be achieved if all the recommendations were implemented.

The certificate is important because nearly 50 per cent of the UK's energy consumption and carbon emissions arise from the way our buildings are lit, heated and used. Even comparatively minor changes in energy performance and the way we use each building will have a significant effect in reducing energy consumption.

EPCS are produced by accredited energy assessors.

The certificate provides a rating for the building, showing its energy efficiency. The ratings are similar to those found on products such as fridges and are standard so the energy efficiency of one building can easily be compared with another building of a similar type.

For homes, two ratings are shown.

The energy-efficiency rating is a measure of a home's overall efficiency. The higher the rating, the more energy-efficient the home is, and the lower the fuel bills are likely to be.

The environmental impact rating is a measure of a home's impact on the environment in terms of carbon dioxide (CO2) emissions - the higher the rating, the less impact it has on the environment.

Each rating is based on the performance of the building itself and its services (such as heating and lighting), rather than the domestic appliances within it. This is known as an asset rating. The certificate also lists the potential rating of the building if all the cost-effective measures were installed.

The ratings will vary according to the age, location, size and condition of the building. The potential rating on the certificate will take these factors into account, and the suggested measures will be tailored so that they are realistic for the particular building.

The certificate also includes a recommendation report, providing information about ways to improve the energy performance of the property. Recommendations include cost effective improvements and further improvements (that achieve higher standards but are not necessarily cost effective). For each improvement the level of cost, typical cost savings per year and the performance rating after improvement are listed. The potential rating shown on the certificate is based on all the cost effective recommendations being implemented.

In addition the EPCs must convey several other key pieces of information:

Reference information
This includes the type of property (e.g. house, flat), the unique reference number (as stored in the central register) and date of the certificate.

Estimated energy use
This is based on standardised assumptions about occupancy and heating patterns. An estimate of the current and potential energy use, carbon emissions and fuel costs for lighting, heating and hot water is provided. The actual energy use depends on the behaviour of the occupants.

Energy Assessor details
This includes the assessor's name, accreditation number, company name (or trading name if self employed) and contact details.

Complaints
The certificate will provide information about how to complain or how to check the certificate is authentic.

Energy advice
The certificate provides basic advice about energy efficient behaviour.