According an expert opinion on the topic, MEES contains two separate requirements: from 1 April 2018, landlords will not be permitted to grant a lease of a property with an EPC rating below E unless they have carried out all possible cost-effective energy efficiency improvement works, or an exemption applies. Then, from 1 April 2020, (in the case of residential properties) or 1 April 2023 (in the case of commercial properties), landlords will not be permitted to continue to let property with an EPC rating below E on an existing lease unless they have carried out all possible cost-effective energy efficiency improvement works, or an exemption applies.