The Standard Assessment Procedure (SAP) is the Government’s recommended calculations system for the home energy rating. The SAP energy cost rating is based on energy costs for space and water heating only. A SAP rating is required for all new build dwellings and those which are undergoing significant material alteration (such as the addition of an extension to the dwelling).
A SAP calculation is simply a home energy rating that shows a score between 1 to 100+ for the annual energy cost due to:
the built structure of the home ( ie. amount of insulation in the walls, floors, roof etc, double glazing windows)
heating and hot water system
any renewable technologies
The higher the score, the lower the fuel running costs, with 100 representing zero energy cost. Dwellings with a rating in excess of 100 are net exporters of energy. A SAP calculation is normally a desk exercise. The assessor does not usually visit the dwelling being assessed.