"An Energy Performance Certificate (EPC) is a legally valid document which provides an energy efficiency rating (displayed on an A-G scale) in relation to a property’s running costs. This rating will take into account the potential energy performance of the property itself (the fabric) and its services (heating, lighting, hot water etc)." Elmhurst Energy
"An EPC is required in the UK whenever a property is marketed for sale or rent or is newly built. The EPC is valid for 10 years or until a newer EPC is produced for the same property. It is recommended that a property’s EPC should be made available to potential buyers as soon as it is marketed for sale or rent." Elmhurst Energy