Since 2013, listed buildings have been exempt from EPCs, provided they reach certain minimum standards for energy performance. Ironically, the best way to check whether your building meets these standards is to get an EPC. If your listed building already had an EPC before the exemption came into place, you will have to make sure it has an E rating before you can rent it out. This may require some changes.
Many common EPC-recommended measures, such as installing insulation or double glazing, can harm the authenticity of a listed building, so it's understandable if you want to try and avoid these. Efficiency improvements which will cause minimal harm to the aesthetics or structural integrity of a listed building include switching to a renewable energy source, installing a more efficient boiler and draught-proofing.