Energy Performance Certificates
It is a legal requirement for a property that is marketed for sale or rent to have an Energy Performance Certificate (EPC).
The certificate rates a property from "A" to "G" for both Energy Efficiency and Environmental Impact with "A" being the best. It also shows how a property could potentially better its rating after making improvements.
These are quick to arrange and last for 10 years, so you will not need another one in a hurry!