Domestic EPCs are used to benchmark the design energy efficiency of homes n comparison to other homes - so helping buyers and renters make informed decisions about the costs associated with living in any given home.
To offer a home for sale or rent, it is usually necessary that it have an in date EPC (within 10 years) meeting the minimum energy efficiency standard (MEES) of an E rating. In some specific cases, an exemption can be applied for such as if the cost of meeting the minimum standard is excessively large, or the available technical options require permissions which cannot be obtained.
Everything else being equal, an A rated home will cost considerably less in energy bills than an E rated home which needs to be factored into affordability calculations, and hence is worth paying a little more to buy or rent.
Most EPCs are done for mandatory reasons, but EPCs can be requested for other reasons such as when a building has been improved and the owner wants this reflected in the EPC, or is needing advice on options to make a home more energy efficient.
An EPC also gives advice on some of the measures which can be taken to make a home more efficient, and I for one am very happy to have a discussion with the client about these options for improvement.