EPCs are required whenever a building is constructed or marketed for sale or rent.
The energy survey needed to produce an EPC is performed by an assessor who visits the property, examines key items such as loft insulation, domestic boiler, hot water tank, radiators, windows for double glazing and so on.
He or she then inputs the observations into a software program which perform the calculation of energy efficiency. The program gives a single number for the rating of energy efficiency, and a recommend value of the potential for improvement.
For homes, two ratings are shown, the current rating and the potential rating. The actual energy-efficiency rating is a measure of a home's overall efficiency. The higher the rating, the more energy-efficient the home is, the lower the associated carbon emissions are and the lower fuel bills are likely to be.