When should an estate agent show the EPC to a prospective buyer?
ASAP. Regulation 5(2) of the Energy Performance of Buildings Directive (EPBD) regulations requires the relevant person to make the EPC available to a prospective buyer at the 'earliest opportunity'.
Therefore an agent who has a HIP (including an EPC) in his possession is under a duty to inform a prospective buyer who shows an interest in the property that the EPC (at least) is available for inspection. In theory this should apply even if the HIP has not been asked for by the prospective buyer.