I have covered this issue in depth before, last year in the video below and in this article on EPC’s.
It’s worth remembering that from the 1st of April 2018 you can’t start a new tenancy with a property rated either F or G on the EPC (Energy Performance Certificate).
I strongly recommend checking your EPC and taking action to improve the rating before this date. Two years later (1st April 2020) the law applies whether there is a new tenancy or not.