Property managers must supply an NPC whenever a home or flat is built, sold or rented.
They split energy ratings into seven lettered bands from most to least efficient, measured by Standard Assessment Procedure (SAP) points.
The bands include:
Band A: 92 to 100 SAP points
Band B: 81 to 91 SAP points
Band C: 69 to 80 SAP points
Band D: 55 to 68 SAP points
Band E: 39 to 54 SAP points
Band F: 21 to 38 SAP points
Band G: 1 to 20 SAP points